Co-reporter:Soumava Biswas, Jayita Chakraborty, Vijay Singh Parmar, Siba Prasad Bera, Nirmal Ganguli, and Sanjit Konar
Inorganic Chemistry May 1, 2017 Volume 56(Issue 9) pp:4956-4956
Publication Date(Web):April 20, 2017
DOI:10.1021/acs.inorgchem.6b03147
Two new lanthanide-based 3D metal–organic frameworks (MOFs), {[Ln(L)(Ox)(H2O)]n·xH2O} [Ln = Gd3+ and x = 3 (1) and Dy3+ and x = 1.5 (2); H2L = mucic acid; OxH2 = oxalic acid] showing interesting magnetic properties and channel-mediated proton conduction behavior, are presented here. Single-crystal X-ray structure analysis shows that, in complex 1, the overall structure originates from the mucate-bridged gadolinium-based rectangular metallocycles. The packing view reveals the presence the two types of hydrophilic 1D channels filled with lattice water molecules, which are strongly hydrogen-bonded with coordinated water along the a and b axes, whereas for complex 2, the 3D framework originates from a carboxylate-bridged dysprosium-based criss-cross-type secondary building block. Magnetic studies reveal that 1 exhibits a significant magnetic entropy change (−ΔSM) of 30.6 J kg–1 K–1 for ΔH= 7 T at 3 K. Our electronic structure calculations under the framework of density functional theory reveal that exchange interactions between Gd3+ ions are weak and of the antiferromagnetic type. Complex 2 shows field-induced single-molecule-magnetic behavior. Impedance analysis shows that the proton conductivity of both complexes reaches up to the maximum value of 4.7 × 10–4 S cm–1 for 1 and 9.06 × 10–5 S cm–1 for 2 at high temperature (>75 °C) and relative humidity (RH; 95%). The Monte Carlo simulations confirm the exact location of the adsorbed water molecules in the framework after humidification (RH = 95%) for 1. Further, the results from computational simulation also reveal that the presence of a more dense arrangement of adsorbed water molecules through hydrogen bonding in a particular type of channel (along the a axis) contributes more to the proton migration compared to the other channel (along the b axis) in the framework.
Co-reporter:Amit Kumar Mondal, Tamal Goswami, Anirban Misra, and Sanjit Konar
Inorganic Chemistry June 19, 2017 Volume 56(Issue 12) pp:6870-6870
Publication Date(Web):May 31, 2017
DOI:10.1021/acs.inorgchem.7b00233
In this work, the effects of ligand field strength as well as the metal coordination geometry on magnetic anisotropy of pentacoordinated CoII complexes have been investigated using a combined experimental and theoretical approach. For that, a strategic design and synthesis of three pentacoordinate CoII complexes [Co(bbp)Cl2]·(MeOH) (1), [Co(bbp)Br2]·(MeOH) (2), and [Co(bbp)(NCS)2] (3) has been achieved by using the tridentate coordination environment of the ligand in conjunction with the accommodating terminal ligands (i.e., chloride, bromide, and thiocyanate). Detailed magnetic studies disclose the occurrence of slow magnetic relaxation behavior of CoII centers with an easy-plane magnetic anisotropy. A quantitative estimation of ZFS parameters has been successfully performed by density functional theory (DFT) calculations. Both the sign and magnitude of ZFS parameters are prophesied well by this DFT method. The theoretical results also reveal that the α → β (SOMO–SOMO) excitation contributes almost entirely to the total ZFS values for all complexes. It is worth noting that the excitation pertaining to the most positive contribution to the ZFS parameter is the dxy → dx2–y2 excitation for complexes 1 and 2, whereas for complex 3 it is the dz2 → dx2–y2 excitation.
Co-reporter:Amit Kumar Mondal;Jesús Jover;Eliseo Ruiz
Chemical Communications 2017 vol. 53(Issue 38) pp:5338-5341
Publication Date(Web):2017/05/09
DOI:10.1039/C7CC02584J
In this work we report two pentacoordinated CoII–P4X1 Single Ion Magnets (SIMs) based on P-donor ligands. The tetradentate ligand tris[2-(diphenylphosphino)ethyl]phosphine allows the obtention of the isostructural square pyramidal [Co(PP3)Cl]·ClO4 (1) and [Co(PP3)Br]·ClO4 (2) complexes. Consistent theoretical and experimental studies indicate that these complexes have a high spin (S = 3/2) ground state and suggest that the relaxation dynamics is governed by ground state quantum tunneling, whereas its temperature dependence is directed by optical or acoustic Raman processes.
Co-reporter:Javeed Ahmad Sheikh, Himanshu Sekhar Jena, Abraham Clearfield, and Sanjit Konar
Accounts of Chemical Research 2016 Volume 49(Issue 6) pp:1093
Publication Date(Web):May 6, 2016
DOI:10.1021/acs.accounts.5b00531
ConspectusTransition metal based high nuclearity molecular magnetic cages are a very important class of compounds owing to their potential applications in fabricating new generation molecular magnets such as single molecular magnets, magnetic refrigerants, etc. Most of the reported polynuclear cages contain carboxylates or alkoxides as ligands. However, the binding ability of phosphonates with transition metal ions is stronger than the carboxylates or alkoxides. The presence of three oxygen donor sites enables phosphonates to bridge up to nine metal centers simultaneously. But very few phosphonate based transition metal cages were reported in the literature until recently, mainly because of synthetic difficulties, propensity to result in layered compounds, and also their poor crystalline properties. Accordingly, various synthetic strategies have been followed by several groups in order to overcome such synthetic difficulties. These strategies mainly include use of small preformed metal precursors, proper choice of coligands along with the phosphonate ligands, and use of sterically hindered bulky phosphonate ligands. Currently, the phosphonate system offers a library of high nuclearity transition metal and mixed metal (3d–4f) cages with aesthetically pleasing structures and interesting magnetic properties.This Account is in the form of a research landscape on our efforts to synthesize and characterize new types of phosphonate based high nuclearity paramagnetic transition metal cages. We quite often experienced synthetic difficulties with such versatile systems in assembling high nuclearity metal cages. Few methods have been emphasized for the self-assembly of phosphonate systems with suitable transition metal ions in achieving high nuclearity. We highlighted our journey from 2005 until today for phosphonate based high nuclearity transition metal cages with VIV/V, MnII/III, FeIII, CoII, NiII, and CuII metal ions and their magnetic properties. We observed that slight changes in stoichiometry, reaction conditions, and presence or absence of coligand played crucial roles in determining the final structure of these complexes. Most of the complexes included are regular in geometry with a dense arrangement of the above-mentioned metal centers in a confined space, and a few of them also resemble regular polygonal solids (Archimedean and Platonic). Since there needs to be a historical approach for a comparative study, significant research output reported by other groups is also compared in brief to ensure the potential of phosphonate ligands in synthesizing high nuclearity magnetic cages.
Co-reporter:Soumava Biswas, Amit Kumar Mondal, and Sanjit Konar
Inorganic Chemistry 2016 Volume 55(Issue 5) pp:2085-2090
Publication Date(Web):February 16, 2016
DOI:10.1021/acs.inorgchem.5b02486
Two isostructural densely packed squarato-bridged lanthanide-based 3D metal–organic frameworks (MOFs) [Ln5(μ3-OH)5(μ3-O)(CO3)2(HCO2)2(C4O4)(H2O)2] [Ln = Gd (1) and Dy (2)] show giant cryogenic magnetic refrigeration (for 1) and slow magnetic relaxation (for 2). The structural analyses reveal the presence of a self-assembled crown-shaped building unit with a cubane-based rectangular moiety that leads to a special array of metal centers in 3D space in the complexes. Magnetic investigations confirm that complex 1 exhibits one of the largest cryogenic magnetocaloric effects among the molecular magnetic refrigerant materials reported so far (−ΔSm = 64.0 J kg–1 K–1 for ΔH = 9 T at 3 K). The cryogenic cooling effect (of 1) is also quite comparable with that of the commercially used magnetic refrigerant gadolinium–gallium garnet, whereas for complex 2, slow relaxation of magnetization was observed below 10 K.
Co-reporter:Amit Kumar Mondal, Himanshu Sekhar Jena, Amita Malviya, and Sanjit Konar
Inorganic Chemistry 2016 Volume 55(Issue 11) pp:5237-5244
Publication Date(Web):May 19, 2016
DOI:10.1021/acs.inorgchem.6b00177
A rare class of four tetranuclear lanthanide based quadruple stranded helicates namely, [Ln4L4(OH)2](OAc)2·xH2O (Ln = GdIII(1), DyIII(2) and x = 4, 5 respectively), [Er4L4(OH)2](NO3)2·9H2O (3), and [Dy4L4(NO3)](NO3)2·2CH3OH·H2O (4) were synthesized by employing succinohydrazone derived bis-tridentate ligand (H2L) and characterized. Structures of 1–3 are similar to each other except the nature of counterions and number of lattice water molecules. In 4, a distorted nitrate ion was arranged in a hexagonal manner holding four dysprosium centers in a slightly twisted manner. Because of the symmetrical nature of each complex, the C4 axis crosses the center of helicate resulting a pseudo-D4 coordination environment. Each ligand coordinates to lanthanide centers in helical manner forming mixture of left (Λ) and right (Δ) handed discrete units. Complex 1 exhibits antiferromagnetic exchange interaction between nearby GdIII centers and shows magnetic refrigeration (−ΔSm = 24.4 J kg–1 K–1 for ΔH = 7 T at 3 K). AC magnetic susceptibility measurements of 2 and 4 demonstrate slow relaxation behavior, with Ueff (effective energy barrier) of 20.5 and 4.6 K, respectively. As per our knowledge, complexes 1, 2, and 4 represent the first examples of aesthetically pleasing quadruple stranded helicates showing potential magnetocaloric effect and single-molecule-magnet-like behavior.
Co-reporter:Ankita Sharma Gangele, Soumyabrata Goswami, Arun Kumar Bar, Priyanka Tiwari, Sanjit Konar, and Anita Dutt Konar
Crystal Growth & Design 2016 Volume 16(Issue 4) pp:2130-2139
Publication Date(Web):February 11, 2016
DOI:10.1021/acs.cgd.5b01803
In an attempt to artificially imitate the importance of side chains in supramolecular architecture stabilization, we have synthesized a set of four model tripeptides Boc-4(X)-Phe-Aib-Yaa-OMe (I–IV), where X = I, F, N3, and Yaa = Ile/Leu, respectively. Our experimental (X-ray crystallography) and computational investigation (differential functional theory calculations) reveals that the tripeptide (I) self-assembles to form a zigzag ribbon-like assemblage between two conformers, a type III β-turn and an open strand, present in the asymmetric unit. In contrast when a slight modification has been incorporated in the side chains in tripeptides II–IV, it does not support the formation of a ribbon-like organization. Instead, significant heterogeneity is displayed within the supramolecular framework. Interestingly, field emission scanning electron microscopy studies also support the morphological diversities present in the peptides arising due to a mere change of terminal side chains. Thus, the importance of co-operative steric interactions among the side chains of amino acid residues is emphasized in stabilizing a particular supramolecular architecture. This research may not only serve to indicate effective candidates in protein modification but also assist in the rational design of peptidomimetics.
Co-reporter:Upendarrao Golla, Amit Adhikary, Amit Kumar Mondal, Raghuvir Singh Tomar and Sanjit Konar
Dalton Transactions 2016 vol. 45(Issue 29) pp:11849-11863
Publication Date(Web):23 Jun 2016
DOI:10.1039/C6DT01496H
Four coordination compounds of formulae [CuII2(H2L1)(HL1)](ClO4)3·H2O (1), [CuII2(H2L2)(CH3OH)2](ClO4)2·2CH3OH (2), [CoII2(H2L1)2](ClO4)4 (3) and [CoII2(H2L2)2]·2H2O (4) were synthesized via self-assembly of succinohydrazone derived ligands (H2L1 = N′,N′-4-bis(2-pyridyl)succinohydrazide, H4L2 = N′,N′-4-bis(2-hydroxybenzylidene)succinohydrazide) and Cu2+ and Co2+ ions, respectively. The compounds were characterized by crystal structure determination, magnetic measurements and biological activities. Compounds 1, 3 and 4 have discrete double helicate structures, whereas compound 2 is a one-dimensional chain. Magnetic studies show antiferromagnetic exchange interactions in 2 with a J value of −67.1 cm−1 and antiferromagnetic spin-canting in compound 3 originates through supramolecular H-bonding. For compound 3, a clear bifurcation was observed in zero field cooled (ZFC) and field cooled (FC) measurement at a temperature of 3.5 K and field of 0.1 T, implying long range magnetic ordering below this temperature. Interestingly, all of compounds 1–4 show significant changes in their absorption (hypo- and hyperchromism) in the presence of SS-DNA, inferring interaction between the compounds and DNA. In addition, compounds 1–4 significantly exhibited nuclease activities on both RNA and pUC19 plasmid DNA. Moreover, the nuclease activity was further enhanced in the presence of oxidant (H2O2) and suggests the possible role of reactive oxygen species in DNA nicking ability of compounds 1–4. Furthermore, compounds 1, 2 and 4 exhibited significant cytotoxicity against mammalian cancer cell lines (HeLa, A549 and MDAMB-231). In addition, our results from Annexin/PI staining and DNA fragmentation assays revealed that these compounds are capable of inducing apoptosis and have potential to act as anticancer drugs.
Co-reporter:Srinivasulu Parshamoni and Sanjit Konar
CrystEngComm 2016 vol. 18(Issue 23) pp:4395-4404
Publication Date(Web):04 Apr 2016
DOI:10.1039/C5CE02542G
Four new Zn(II)-based metal organic frameworks (MOFs), namely, [Zn(tdc)(4-bpmh)]n·n(H2O) (1), [Zn(2-NH2BDC)(4-bpmh)]n·n(EtOH) (2), [Zn(NDC)(4-bpmh)]n (3) and {[Zn(ADPA)(4-bpmh)(H2O)](ClO4)}n·n(MeOH) (4) (tdc = 2,5-thiophene dicarboxylic acid, 2-NH2BDC = 2-aminoterephthalic acid, NDC = 2,6-naphthalene dicarboxylic acid, ADPA = adipic acid, 4-bpmh = N,N-bis-pyridin-4-ylmethylene-hydrazine) have been synthesized through the slow diffusion technique using a 4-bpmh linker and different dicarboxylic acids. Structural analysis reveals that compounds 1–3 have 3D networks with diamondoid (dia) topologies whereas compound 4 has a 2D pillared-trilayer framework with sql/Shubnikov tetragonal plane net topology. Compounds 1–2 have 6-fold interpenetrated nets and compound 3 is a 7-fold interpenetrated net. Gas adsorption studies reveal that all the compounds 1–4 show selective adsorption of CO2 over other gases (N2, CH4) at low temperature, and the uptake amount of compound 2 is almost double in comparison with those of compounds 1, 3 and 4.
Co-reporter:Amit Kumar Mondal, Vijay Singh Parmar, Soumava Biswas and Sanjit Konar
Dalton Transactions 2016 vol. 45(Issue 11) pp:4548-4557
Publication Date(Web):2016/01/25
DOI:10.1039/C5DT04173B
A rare class of dinuclear double-stranded helicates having tetrahedral metal centres with formulae [Co2(L1)2]·2(CH3CN) (1), [Co2(L2)2]·6(CH3CN) (2), [Zn2(L1)2]·2(CH3CN)·(CH3OH) (3) and [Zn2(L2)2]·4(CH3CN) (4) were synthesized and characterized. Detailed dc and ac magnetic susceptibility measurements reveal the presence of field induced slow magnetic relaxation behaviour in high spin tetrahedral CoII centres with an easy-plane magnetic anisotropy. Complexes 1 and 2 are the rare examples of transition metal based helicates showing such behaviour. Furthermore, 3 and 4 exhibit fluorescence emission in different solvents that are analyzed in terms of fluorescence quantum yields and lifetimes.
Co-reporter:Amit Kumar Mondal;Sajal Khatua;Kapil Tomar
European Journal of Inorganic Chemistry 2016 Volume 2016( Issue 22) pp:
Publication Date(Web):
DOI:10.1002/ejic.201670221
Co-reporter:Amit Kumar Mondal;Sajal Khatua;Kapil Tomar
European Journal of Inorganic Chemistry 2016 Volume 2016( Issue 22) pp:
Publication Date(Web):
DOI:10.1002/ejic.201600847
Abstract
Invited for the cover of this issue is the group of Dr. Sanjit Konar from the Indian Institute of Science Education and Research, Bhopal, India. The cover image shows field-induced slow magnetic relaxation of an octahedral CoII center in a two-dimensional coordination polymer. The rare [4+4] metallocyclic building blocks lead to separated, magnetically isolated CoII centers, which show slow relaxation.
Co-reporter:Srinivasulu Parshamoni;Jyothi Telangae;Suresh Sa ;Dr. Sanjit Konar
Chemistry – An Asian Journal 2016 Volume 11( Issue 4) pp:540-547
Publication Date(Web):
DOI:10.1002/asia.201501084
Abstract
A copper(I)-based metal–organic framework ({[Cu2Br2(pypz)]n⋅nH2O} (Cu—Br–MOF) [pypz=bis[3,5-dimethyl-4-(4’-pyridyl)pyrazol-1-yl] methane] has been synthesized by using an elongated and flexible bridging ligand. The structure analysis reveals that each pypz ligand acts as a tritopic ligand connected to two Cu2Br2 dimeric units, forming a one-dimensional zig–zag chain, and these chains further connected by a Cu2Br2 unit, give a two-dimensional framework on the bc-plane. In the Cu2Br2 dimeric unit, the copper ions are four coordinated, thereby possessing a tetrahedral geometry; this proves to be an excellent heterogeneous catalyst for the aerobic homocoupling of arylboronic acids under mild reaction conditions. This method requires only 3 mol % of catalyst and it does not require any base or oxidant—compared to other conventional (Cu, Pd, Fe, and Au) catalysts—for the transformation of arylboronic acids in very good yields (98 %). The shape and size selectivity of the catalyst in the homocoupling was investigated. The use of the catalyst was further extended to the epoxidation of olefins. Moreover, the catalyst can be easily separated by simple filtration and reused efficiently up to 5 cycles without major loss of reactivity.
Co-reporter:Sajal Khatua, Soumyabrata Goswami, Soumava Biswas, Kapil Tomar, Himanshu Sekhar Jena, and Sanjit Konar
Chemistry of Materials 2015 Volume 27(Issue 15) pp:5349
Publication Date(Web):July 8, 2015
DOI:10.1021/acs.chemmater.5b01773
A novel Cu(I)-based two-dimensional (2D, 44 net) metal–organic framework (MOF) [Cu(L)(I)]2n·2nDMF·nMeCN (1); L = 4′-(4-methoxyphenyl)-4,2′:6′,4″-terpyridine; DMF = N,N-dimethylformamide, MeCN = acetonitrile) has been synthesized and found to behave as a colorimetric detector for the widest variety of small molecules such as different solvents, halobenzenes, N-heterocycles, amine, and nitroaromatic explosives all in vapor phase through a single crystal to single crystal (SCSC) transformation. The 2D 44 nets are interdigitated with each other to form a supramolecular 3D MOF having 1D pore. The interdigitated layers are stabilized by π···π interactions and CH···π interactions and provide extreme stability up to 380 °C. Interestingly, all guest exchange and encapsulation processes are reversible without loss of structural integrity. Positions of the guest molecules in the host–guest complex have been identified from the crystal structure and found to involve weak interactions with the framework. Notably, this is the first time for a report of any material which encapsulates such a large number of small molecules in the vapor phase from different chemical classes in SCSC fashion with visible color changes. Tests confirm the selectivity toward most polar molecule in a class. In the presence of guest molecules, the MOF exhibits a blue shift in fluorescence emission spectra and the extent of the blue shift is appreciably high. It also shows high selectivity toward diethylamine (dea) among N-heterocycles, amine, and highly explosive trinitrophenol (TNP) among nitroaromatic explosives as revealed from concurrent luminescence quenching in solution. Finally, the MOF represents one of the best hosts reported so far having extreme stability and selectivity and meets the benchmark of reversibility for material applications.
Co-reporter:Suresh Sanda, Srinivasulu Parshamoni, Soumava Biswas and Sanjit Konar
Chemical Communications 2015 vol. 51(Issue 30) pp:6576-6579
Publication Date(Web):04 Mar 2015
DOI:10.1039/C4CC10442K
A Zn(II) based luminescent metal organic framework is synthesized, which acts as a dual functional fluorescent sensor to selectively detect picric acid and palladium(II).
Co-reporter:Prasath Rangaraj, Srinivasulu Parshamoni and Sanjit Konar
Chemical Communications 2015 vol. 51(Issue 85) pp:15526-15529
Publication Date(Web):28 Aug 2015
DOI:10.1039/C5CC06311F
In a new concept, an iodine loaded amine functionalized MOF was employed as a syringe pump for the slow release of iodine as a catalyst in the synthesis of thienyl dipyrromethanes under ambient conditions and turned out to be successful. The catalytic activities were compared with an isoreticular non-functionalized MOF and other conventional catalysts.
Co-reporter:Suresh Sanda, Soumava Biswas, and Sanjit Konar
Inorganic Chemistry 2015 Volume 54(Issue 4) pp:1218-1222
Publication Date(Web):January 16, 2015
DOI:10.1021/ic502098h
We report the proton conduction properties of a 2D flexible MOF and a 1D coordination polymer having the molecular formulas {[Zn(C10H2O8)0.5(C10S2N2H8)]·5H2O]}n (1) and {[Zn(C10H2O8)0.5(C10S2N2H8)]·2H2O]}n (2), respectively. Compounds 1 and 2 show high conductivity values of 2.55 × 10–7 and 4.39 × 10–4 S cm–1 at 80 °C and 95% RH. The conductivity value of compound 1 is in the range of those for previously reported flexible MOFs, and compound 2 shows the highest proton conductivity among the carboxylate-based 1D CPs. The dimensionality and the internal hydrogen bonding connectivity play a vital role in the resultant conductivity. Variable-temperature experiments of both compounds at high humidity reveal that the conductivity values increase with increasing temperature, whereas the variable humidity studies signify the influence of relative humidity on high-temperature proton conductivity. The time-dependent measurements for both compounds demonstrate their ability to retain conductivity up to 10 h.
Co-reporter:Amit Adhikary, Himanshu Sekhar Jena and Sanjit Konar
Dalton Transactions 2015 vol. 44(Issue 35) pp:15531-15543
Publication Date(Web):24 Jul 2015
DOI:10.1039/C5DT01569C
Herein, the synthesis, structural characterization, magnetic properties and guest binding activities of four Fe3+ based double-stranded helicates namely; [Fe2(L)2](ClO4)(Cl)·4(CH3OH)·2(H2O) (1), [Fe2(L)2](BF4)2·2(H2O) (2), [Fe2(L)2](NO3)2·3(CH3OH)·2(H2O) (3), and [Fe2(L)2](Cl)2·2(CH3OH)·4(H2O) (4) are reported. Complexes 1–4 have been synthesized using the hydrazide-based ligand H2L (H2L = N′1,N′4-bis(2-hydroxybenzylidene)succinohydrazide) and the corresponding Fe2+ salts. Each of the independent cationic complexes [Fe2(L)2]2+ shows double-stranded helicates from the self-assembly of the ligand and metal ions in a 2:2 ratio, where the individual Fe3+ centre is lying on a C2-axis and the ligand strands wrap around it. In 1–4, ligand L adopts “pseudo-C” conformations and forms a double-stranded dinuclear helicate with a small cage in between them. Moreover, in 1–4, each of the independent cationic complexes [Fe2L2]2+ is inherently chiral and possesses P for right-hand and M for left-hand helicity and as a consequence is a racemic solid. Detailed magnetic studies of all the complexes reveal that the Fe3+ centres are magnetically isolated and isotropic in nature. Estimation of the Magnetocaloric Effect (MCE) from magnetization data unveils a moderate MCE at a temperature of 3 K with magnetic entropy changes (−ΔSm) of 22.9, 27.7, 24.1, 26.5 J kg−1 K−1 at a magnetic field of 7 T for complexes 1–4, respectively. Also, the variation of the −ΔSm values was justified by considering the parameter of magnetization per unit mass. Stability of all the complexes in solution phase was confirmed by ESI-mass spectrometric analysis and liquid phase FT-IR spectroscopy. Further, the interaction of the complexes 1–4 with Rhodamine B dye was examined by UV-vis and fluorescence spectroscopic study. The observed blue-shift in the fluorescence study and hyperchromicity and hypochromicity with the appearance of two isosbestic points in the UV-vis study ascertain the interactions of the dye with the complexes. A DNA binding study by absorption spectral titration suggests the weak external intercalation of complex 1 within the nucleotide of calf thymus DNA. Computational study supports the isotropic nature of the metal centres and the consequent high spin multiplicity, which assists the complexes to show significant magnetic entropy changes.
Co-reporter:Amit Kumar Mondal, Soumyabrata Goswami and Sanjit Konar
Dalton Transactions 2015 vol. 44(Issue 11) pp:5086-5094
Publication Date(Web):30 Jan 2015
DOI:10.1039/C4DT03620D
The reaction of 2,6-bis(1-salicyloylhydrazonoethyl)pyridine [H4daps] with Dy(NO3)3·5H2O led to the formation of two new Dy(III) based complexes with formulae [Dy(H4daps)(H2O)3(NO3)] (NO3)2 (H2O) (1) and [Dy(H3daps)(H2O)2(NO3)] (NO3) (MeOH) (2). Complexes 1 and 2 were characterized by crystal structure determination, magnetic measurements and photoluminescence studies. In comparison with complex 1, complex 2 shows a slight difference of local symmetry around the Dy(III) center which is attributed to deprotonation of the ligand and also to different binding modes of the peripheral NO3− anion. AC magnetic susceptibility measurements reveal that both complexes exhibit single-molecule magnet (SMM) behavior, with the thermal energy barrier of 1 being higher than that of 2 (Ueff = 32.7 K for 1 and 23.8 K for 2). Our investigation discloses that small differences in the coordination environment around the metal centre played an important role in the difference in relaxation dynamics of the complexes. Solid state photoluminescence studies showed their photoluminescence behaviour with quantum yields of 0.98 and 1.44%.
Co-reporter:Soumyabrata Goswami, Soumava Biswas and Sanjit Konar
Dalton Transactions 2015 vol. 44(Issue 9) pp:3949-3953
Publication Date(Web):22 Jan 2015
DOI:10.1039/C4DT03575E
Two unprecedented oxonate based 1D coordination polymers with FeII and CoII have been synthesized. A detailed magnetic investigation revealed that these complexes are the first oxonate based systems to exhibit spin canted antiferromagnetic ordering at low temperatures. Proton conductivity studies of the complexes showed good proton conduction ability at elevated temperatures and under high humidity conditions.
Co-reporter:Kapil Tomar, Richa Rajak, Suresh Sanda, and Sanjit Konar
Crystal Growth & Design 2015 Volume 15(Issue 6) pp:2732
Publication Date(Web):March 27, 2015
DOI:10.1021/acs.cgd.5b00056
Six porous metal–organic frameworks (MOFs), {[Ni(BTC)0.66(BPz)2]·2MeOH·4H2O}n (1), {[Co(BTC)0.66(BPz)2]·2MeOH·4H2O}n (2), {[Mn(BTC)0.66(BPz)2]·2MeOH·4H2O}n (3), {[Cd(BDC)(BPz)(H2O)]·2MeOH·DMF}n (4), {[Cd2(NH2-BDC)2(BPz)(H2O)]·MeOH·H2O·DMF}n (5), and {[Co(BDC)(BPz)(H2O)]}n (6) (where H3BTC = 1,3,5-benzenetricarboxylic acid, H2BDC = 1,4-benzenedicarboxylic acid, NH2-H2BDC = 2-amino-1,4-benzenedicarboxylic acid, and BPz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole), were obtained through a solvent diffusion technique and characterized. The networks exhibit a variety of topologies: 1, 2, and 3 are isostructural and possess octahedral and cuboctahedra type cages and exhibit 3,6-c binodal net having loh1 topology, 4 is a two-dimensional MOF having one-dimensional open channels with a 4-c uninodal net having sql topology, 5 exhibits a three-dimensional (3D) porous MOF having a 3,3,4,8-c net with a new topology having the name, skr1, whereas 6 discloses a 3D nonporous network which exhibits a 4-c uninodal net having CdSO4 topology. Being isostructural, gas sorption studies of 1–3 show nearly the same CO2 sorption at 195 K of ∼90 mL g–1, whereas 4 and 5 show a maximum uptake of 42 and 37 mL g–1 at 195 K. Vapor sorption studies of 1–3 reveal stepwise uptake of water with a final amount reached to nearly 350 mL g–1, whereas 4 and 5 show maximum uptake of 110 and 90 mL g–1, respectively. Compared to the free ligand BPz, photoluminescence studies of 4 and 5 show red shifts and emit in the blue-green region with λmax at 430 and 472 nm for 4 and 5, respectively.
Co-reporter:Amita Malviya;Himanshu Sekhar Jena;Amit Kumar Mondal
European Journal of Inorganic Chemistry 2015 Volume 2015( Issue 17) pp:2901-2907
Publication Date(Web):
DOI:10.1002/ejic.201500301
Abstract
Two europium-based helicates, namely the dinuclear triple-stranded helicate [Eu2L3] (1) and tetranuclear quadruple-stranded helicate [Eu4L4(NO3)]3+ (2), were achieved by the self-assembly of the succinohydrazone derived bis-tridentate ligand (H2L) and Eu3+ ions in 1:1 and 1:2 ratios, respectively. Both the helicates were characterized by single-crystal X-ray analysis. Structural analysis of both the helicates revealed optically inactive 50:50 mixtures of left- (Λ) and right-hand (Δ) helicates in one unit cell. In 1, both the europium centers lie along the three-fold axis whereas in 2, four europium centers are arranged in a triangular fashion around the four-fold axis, which passes through the center of the quadruple stranded helicate. In 2, the presence of a nitrate ion on the nucleation of the aesthetically pleasing tetranuclear quadruple stranded helicate is significant. Apart from the molar ratio, the role of the bridging modes of the ligand, anion and noncovalent interaction on the self-assembly of two helicates are also discussed.
Co-reporter:SOUMYABRATA GOSWAMI;AMIT KUMAR MONDAL
Journal of Chemical Sciences 2015 Volume 127( Issue 2) pp:257-264
Publication Date(Web):2015 February
DOI:10.1007/s12039-015-0771-8
A new Co(II)-based three-dimensional (3D) framework having the molecular formula [Co(C4O4) (4-bpmh))H2O)2]n⋅ 2nH2O⋅2nMeOH ⋅(1) (4-bpmh = N, N-bis-pyridin-4-ylmethylene-hydrazine) has been synthesized using a mixed ligand system and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, single crystal X-ray diffraction and variable temperature magnetic study. The framework is constructed by the bridging squarate (C\(_{\mathrm{4}}$O$_{\mathrm{4}}^{\mathrm{2-}}) \) and N, N-bis-pyridin-4-ylmethylene-hydrazine (4-bpmh) ligands and interpenetration of the 2D grid-like frameworks at definite angles gives rise to 2D → 3D inclined polycatenation with sql/Shubnikov tetragonal plane net topology. Extensive non-covalent interactions (H-bonding as well as π⋯π interactions) are also observed which stabilises the 3D arrangement. Additionally, complex 1 contains 1D channels of large dimensions (10.91 × 11.78 Å2) that runs along the b-axis. Variable temperature DC magnetic susceptibility study reveals dominant spin–orbit coupling effect typical of the 4T1g ground state of octahedral high-spin Co(II) ion at a higher temperature range.
Co-reporter:Soumava Biswas;Himanshu Sekhar Jena;Suresh Sa ;Dr. Sanjit Konar
Chemistry - A European Journal 2015 Volume 21( Issue 39) pp:13793-13801
Publication Date(Web):
DOI:10.1002/chem.201501526
Abstract
Three isostructural lanthanide-based two- dimensional coordination polymers (CPs) {[Ln2(L)3(H2O)2]n⋅2n CH3OH)⋅2n H2O} (Ln=Gd3+ (1), Tb3+ (2), Dy3+ (3); H2L=cyclobutane-1,1-dicarboxylic acid) were synthesized by using a low molecular weight dicarboxylate ligand and characterized. Single-crystal structure analysis showed that in complexes 1–3 lanthanide centers are connected by μ3-bridging cyclobutanedicarboxylate ligands along the c axis to form a rod-shaped infinite 1D coordination chain, which is further linked with nearby chains by μ4-connected cyclobutanedicarboxylate ligands to form 2D CPs in the bc plane. Viewing the packing of the complexes down the b axis reveals that the lattice methanol molecules are located in the interlayer space between the adjacent 2D layers and form H-bonds with lattice and coordinated water molecules to form 1D chains. Magnetic properties of complexes 1–3 were thoroughly investigated. Complex 1 exhibits dominant ferromagnetic interaction between two nearby gadolinium centers and also acts as a cryogenic magnetic refrigerant having a significant magnetic entropy change of −ΔSm=32.8 J kg−1 K−1 for ΔH=7 T at 4 K (calculated from isothermal magnetization data). Complex 3 shows slow relaxation of magnetization below 10 K. Impedance analysis revealed that the complexes show humidity-dependent proton conductivity (σ=1.5×10−5 S cm−1 for 1, σ=2.07×10−4 S cm−1 for 2, and σ=1.1×10−3 S cm−1 for 3) at elevated temperature (>75 °C). They retain the conductivity for up to 10 h at high temperature and high humidity. Furthermore, the proton conductivity results were correlated with the number of water molecules from the water-vapor adsorption measurements. Water-vapor adsorption studies showed hysteretic and two-step water vapor adsorption (182000 μL g−1 for 1, 184000 μL g−1 for 2, and 1874000 μL g−1 for 3) in the experimental pressure range. Simulation of water-vapor adsorption by the Monte Carlo method (for 1) confirmed the high density of adsorbed water molecules, preferentially in the interlayer space between the 2D layers.
Co-reporter:Srinivasulu Parshamoni;Suresh Sa;Dr. Himanshu Sekhar Jena ;Dr. Sanjit Konar
Chemistry – An Asian Journal 2015 Volume 10( Issue 3) pp:653-660
Publication Date(Web):
DOI:10.1002/asia.201403123
Abstract
The synthesis and characterization of two isoreticular metal–organic frameworks (MOFs), {[Cd(bdc)(4-bpmh)]}n⋅2 n(H2O) (1) and {[Cd(2-NH2bdc)(4-bpmh)]}n⋅2 n(H2O) (2) [bdc=benzene dicarboxylic acid; 2-NH2bdc=2-amino benzene dicarboxylic acid; 4-bpmh=N,N-bis-pyridin-4-ylmethylene-hydrazine], are reported. Both compounds possess similar two-fold interpenetrated 3D frameworks bridged by dicarboxylates and a 4-bpmh linker. The 2D Cd-dicarboxylate layers are extended along the a-axis to form distorted square grids which are further pillared by 4-bpmh linkers to result in a 3D pillared-bilayer interpenetrated framework. Gas adsorption studies demonstrate that the amino-functionalized MOF 2 shows high selectivity for CO2 (8.4 wt % 273 K and 7.0 wt % 298 K) over CH4, and the uptake amounts are almost double that of non-functional MOF 1. Iodine (I2) adsorption studies reveal that amino-functionalized MOF 2 exhibits a faster I2 adsorption rate and controlled delivery of I2 over the non-functionalized homolog 1.
Co-reporter:Soumava Biswas, Himanshu Sekhar Jena, Amit Adhikary, and Sanjit Konar
Inorganic Chemistry 2014 Volume 53(Issue 8) pp:3926-3928
Publication Date(Web):April 1, 2014
DOI:10.1021/ic4030316
Two isostructural lanthanide-based 3D coordination networks [Ln = Gd3+ (1), Dy3+(2)] with densely packed distorted cuboid nanoscopic cages are reported for the first time. Magnetic characterization reveals that complex 1 shows a significant cryogenic magnetocaloric effect (−ΔSm = 44 J kg–1 K–1), whereas 2 shows slow relaxation of magnetization.
Co-reporter:Soumyabrata Goswami, Himanshu Sekhar Jena, and Sanjit Konar
Inorganic Chemistry 2014 Volume 53(Issue 14) pp:7071-7073
Publication Date(Web):June 30, 2014
DOI:10.1021/ic5003258
We present here a simple, milder, and environmentally benign heterogeneous catalytic method for the transformation of tetrazines to oxadiazole derivatives at room temperature (25 °C) using our earlier synthesized iron-squarate based 3D metal organic framework, [Fe3(OH)3(C4O4)(C4O4)0.5]n (FeSq-MOF).
Co-reporter:Javeed Ahmad Sheikh, Amit Adhikary, Himanshu Sekhar Jena, Soumava Biswas, and Sanjit Konar
Inorganic Chemistry 2014 Volume 53(Issue 3) pp:1606-1613
Publication Date(Web):January 17, 2014
DOI:10.1021/ic402673v
The synthesis, structural characterization, and magnetic property studies of five new transition metal (M = Co, Ni) phosphonate-based cages are reported. Three substituted phenyl and benzyl phosphonate ligands [RPO3H2; R1 = p-tert-butylbenzyl, R2 = p-tert-butylphenyl, R3 = 3-chlorobenzyl] were synthesized and employed to seek out high-nuclearity cages. Complexes 1–3 are quasi-isostructural and feature a dodecanuclear metal-oxo core having the general molecular formula of [M12(μ3-OH)4 (O3PR)4(O2CtBu)6 (HO2CtBu)6(HCO3)6] {M = Co, Ni and R = R1 for 1 (Co12), R2 for 2, 3 (Co12, Ni12)}. The twelve metal centers are arranged at the vertices of a truncated tetrahedron in a manner similar to Keggin ion. Complex 4 is an octanuclear nickel phosphonate cage [Ni8(μ3-OH)4 (OMe)2(O3PR1)2 (O2CtBu)6(HO2CtBu)8], and complex 5 represents a pentadecanuclear cobalt phosphonate cage, [Co15(chp)8(chpH) (O3PR3)8(O2CtBu)6], where chpH = 6-chloro-2-hydroxypyridine. Structural investigation reveals some interesting geometrical features in the molecular cores, which may provide new models in single molecular magnetic materials. Magnetic property measurements of compounds 1–5 indicate the coexistence of both antiferromagnetic and ferromagnetic interactions between magnetic centers for all cages.
Co-reporter:Suresh Sanda, Soumyabrata Goswami, Himanshu Sekhar Jena, Srinivasulu Parshamoni and Sanjit Konar
CrystEngComm 2014 vol. 16(Issue 22) pp:4742-4752
Publication Date(Web):14 Jan 2014
DOI:10.1039/C3CE42451K
Three flexible metal–organic frameworks (MOFs) based on aldrithiol linker and pyromellitate ligand, namely, [Co(aldrithiol)(pyromellitate)0.5(H2O)2]n (1), [Ni2(aldrithiol)2(pyromellitate)(H2O)2]n·2n(C2H5OH)·11n(H2O) (2) and [Cu(aldrithiol)2(pyromellitate)]n·2n(H2O) (3) have been synthesized through slow diffusion technique and characterized by structural, magnetic and adsorption studies. Single crystal X-ray studies show that compounds 1 and 3 have two-dimensional layered structures, whereas compound 2 adopts a three-dimensional framework structure. The observed dimensionality change might be due to the different orientation of pyridine rings in the flexible aldrithiol linker and versatile bridging modes of the pyromellitate ligand. In 1 and 2, the pyromellitate ligand coordinates to the metal centre in a monodentate fashion {(κ1)-(κ1)-(κ1)-(κ1)-μ4} and in 3, it coordinates in {(κ1)-(κ1)-μ2} fashion. The magnetic properties of 1–3 were investigated in detail and show weak antiferromagnetic coupling among the metal centres. Vapour sorption studies reveal that compounds 1 and 3 show high methanol vapour uptake, whereas compound 2 shows a decent amount of H2O adsorption. The dehydrated frameworks of 1–3 regenerate the as-synthesized framework structures upon exposure to water vapour.
Co-reporter:Soumava Biswas, Himanshu Sekhar Jena, Soumyabrata Goswami, Suresh Sanda, and Sanjit Konar
Crystal Growth & Design 2014 Volume 14(Issue 3) pp:1287-1295
Publication Date(Web):February 3, 2014
DOI:10.1021/cg401804e
Two novel isostructural lanthanide- based three-dimensional (3D) metal organic frameworks (MOFs), [Ln2(pam)3(DMF)2(H2O)2]n·nDMF {Ln = Gd(1), Dy(2); H2pam = 4,4′-methylenebis[3-hydroxy-2-naphthalenecarboxylic acid]} using the pharmaceutical agent “pamoic acid (H2pam)” are synthesized for the first time. Single crystal structure analysis shows that the 3D framework originates from the self-assembly of lanthanide metallomacrocycles made of dumble-shaped basic secondary building units and having channels of sizes 17.427 × 15.163 Å (for 1) and 14.58 × 17.23 Å (for 2), respectively. In both the complexes, two eight-coordinated lanthanide centers are connected with six pamoate groups to give a paddle-wheel type building block. The arrangement of pamoates and lanthanides in the framework provokes both right- (P) and left-hand (M) helicity around the 21 screw axis. The magnetic measurements show that complex 1 acts as a cryogenic magnetic refrigerant having magnetic entropy change, −ΔSm, of 17.25 J kg–1 K–1(ΔH = 7 T at 3 K), and complex 2 shows slow relaxation of magnetization. The adsorption studies reveal that complexes 1 and 2 show selectivity toward CO2 sorption over other gases and exhibit high methanol vapor uptake (227 cm3 g–1 for 1 and 201 cm3 g–1 for 2). Solid state photoluminescence properties reveal that they are photoluminescent materials.
Co-reporter:Srinivasulu Parshamoni, Suresh Sanda, Himanshu Sekhar Jena, Kapil Tomar, and Sanjit Konar
Crystal Growth & Design 2014 Volume 14(Issue 4) pp:2022-2033
Publication Date(Web):March 3, 2014
DOI:10.1021/cg500149s
Four new compounds (two coordination polymers (CPs) and two metal organic frameworks (MOFs)), namely, [Zn(cpp)(H2O)]n (1), [Cu(cpp)(4-bpmh)]n·nH2O·nMeOH (2), [Cd2(cpp)2(3-bpmh)2]n4nH2O·2nMeOH (3), and [Cd(cpp)(bpy)(H2O)2]n·2nH2O (4), have been synthesized through the slow diffusion technique using cpp ligand and different neutral linkers (H2cpp = 3-(4-carboxyphenyl)propionic acid, 4-bpmh = N,N-bis-pyridin-4-ylmethylene-hydrazine, 3-bpmh = N,N-bis-pyridin-3-ylmethylene-hydrazine, bpy = 4,4-bipyridine). Single crystal X-ray analysis of compounds 1–4 reveals their structural diversities which might have been generated due to both rigidity (aryl carboxylate) and flexibility (aliphatic carboxylates) of cpp ligands as well their bridging modes and the orientation of nitrogen atoms of the neutral linkers. In addition, the dihedral angle in the aliphatic carboxylates of cpp ligand is also playing an important role in directing the final structural arrangement. Compound 1 exhibits a uninodal 6-connected three-dimensional (3D) coordination polymer with point Schälfli symbol {33.59.63} and shows an uncommon lcy; 6/3/c1 topological type. Compound 2 reveals a 6-connected uninodal 3D framework with point Schälfli symbol {48.66.8} and shows a rare rob topology. Compound 3 formed a 4-connected uninodal two-dimensional framework with point Schälfli symbol {44.62} and displays a sql/Shubnikov tetragonal plane net topology, whereas 4 forms a one-dimensional CP which subsequently extended to 3D supramolecular networks through hydrogen bonding interactions. Gas adsorption studies reveal that compounds 1 and 2 show selective adsorption of CO2 over other gases (N2, CH4) at low temperature, whereas 3 and 4 show no uptake. Vapor sorption studies reveal that compounds 1, 2, and 4 show high uptake capacities for H2O over MeOH and EtOH. Solid state luminescence studies of compounds 1, 3, and 4 display significant red shifts compared to free ligands.
Co-reporter:Srinivasulu Parshamoni, Suresh Sanda, Himanshu Sekhar Jena and Sanjit Konar
Dalton Transactions 2014 vol. 43(Issue 19) pp:7191-7199
Publication Date(Web):14 Feb 2014
DOI:10.1039/C4DT00228H
A new 2D pillared-bilayer flexible open metal organic framework {[Cu(tdc)(bpe)]n·2n(H2O)·n(MeOH)} (compound 1) [H2tdc = 2,5 thiophenedicarboxylic acid; bpe = 1,2-bis(4-pyridyl)ethane] has been synthesized through a solvent diffusion technique and structurally characterized. The structure analysis reveals that the tdc ligands formed bilayers with the Cu(II) ions along the b-direction and the layers are further pillared by bpe linkers and resulted in a 2D pillared-bilayer porous framework with a four connected uninodal sq1/Shubnikob tetragonal plane net with the Schälfli symbol {44·62}. The framework is enclosed with large square shaped channels (13.7 × 8.35 Å2) along the bc-plane and the channels are occupied by guest solvent molecules. The adsorption studies reveal that compound 1 shows selective adsorption for CO2 over CH4 at room temperature and it also shows hysteretic sorption for a few protic solvents (H2O and EtOH) and a Type-1 isotherm for an aprotic solvent (CH3CN). The catalytic performance of compound 1 for Glaser type homo-coupling reactions has also been reported.
Co-reporter:Amit Adhikary, Javeed Ahmad Sheikh, Soumava Biswas and Sanjit Konar
Dalton Transactions 2014 vol. 43(Issue 24) pp:9334-9343
Publication Date(Web):25 Mar 2014
DOI:10.1039/C4DT00540F
The synthesis, crystal structure and magnetic properties of four polynuclear lanthanide coordination complexes having molecular formulae, [Gd3L12(H2O)8(Cl)](Cl)4·10H2O (1), [Dy3L12(H2O)9](Cl)5·6H2O (2) [Gd6L22(HCO2)4(μ3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (3) and [Dy6L22(HCO2)4(μ3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (4) (where H2L1 = bis[(2-pyridyl)methylene]pyridine-2,6-dicarbohydrazide and H4L2 = bis[2-hydroxy-benzylidene]pyridine-2,6-dicarbohydrazide) are reported. Structural investigation by X-ray crystallography reveals similar structural features for complexes 1 and 2 and they exhibit butterfly like shapes of the molecules. Non-covalent interactions between the molecules create double helical arrangements for both molecules. Complexes 3 and 4 are isostructural and the core structures feature four distorted hemi-cubanes connected by vertex sharing. Magnetic studies unveil significant magnetic entropy changes for complexes 1, 3 and slow relaxation of magnetization for both dysprosium analogues 2 and 4.
Co-reporter:Himanshu Sekhar Jena, Soumyabrata Goswami, Suresh Sanda, Srinivasulu Parshamoni, Soumava Biswas and Sanjit Konar
Dalton Transactions 2014 vol. 43(Issue 45) pp:16996-16999
Publication Date(Web):16 Oct 2014
DOI:10.1039/C4DT02496F
We present a robust two dimensional coordination polymer, [Ni2(L)2(N(CN)2)2]n (1) (LH = 2-((1-(pyridin-2-yl)ethylimino)methyl)phenol; N(CN)2− = dicyanamide ion) using a chiral Schiff base (LH), which shows diastereoselectivity in the structure via a chiral self-discrimination process, ferro- and antiferromagnetic interactions among the metal centers and unusual CO2 uptake behavior as a porous framework
Co-reporter:Soumyabrata Goswami, Suresh Sanda and Sanjit Konar
CrystEngComm 2014 vol. 16(Issue 3) pp:369-374
Publication Date(Web):15 Oct 2013
DOI:10.1039/C3CE41612G
A three-dimensional (3D) porous metal organic framework namely, {[Cu3(N3)2(4-ptz)4(DMF)2]·2DMF}n, has been synthesized using Cu(CH3COO)2·H2O and ligand 4-ptz [5-(4-pyridyl)-tetrazolate] which was formed in situ from 4-cyanopyridine and sodium azide in presence of water and CuII ions. Crystal structure analysis showed that the complex crystallizes in the monoclinic space group P21/c and has a decorated body centred cubic (bcu) topological net with 8-connected Cu3 cluster as node. Magnetic studies exhibit prominent antiferromagnetic interactions influenced by EO (end on) azide and μ2,η2-tetrazolato bridge among the metal centres. Gas adsorption studies reveal moderate carbon dioxide uptake, which is also reflected in the isosteric heat of adsorption (Qst) value of −28 kJ mol−1.
Co-reporter:Amit Adhikary;Soumyabrata Goswami;Javeed Ahmad Sheikh
European Journal of Inorganic Chemistry 2014 Volume 2014( Issue 6) pp:963-967
Publication Date(Web):
DOI:10.1002/ejic.201301536
Abstract
The synthesis, characterization, magnetic properties, and magnetostructural correlation of a square-grid complex having the molecular formula [Cu16L18](dmf)3 (1) {H4L1 = 2,6-bis[(3-methoxysalicylidene)hydrazinecarbonyl]pyridine} is described. Reaction of the H4L1 ligand and the Cu2+ salt generates complex 1, which exhibits a rare grid structure with a [4×4] metallic core of Cu2+. Structural studies revealed a mixed coordination geometry around the Cu2+ core. The molecule has a fourfold rotational axis and one inversion center. Magnetic investigations showed the coexistence of both ferro- and antiferromagnetic spin exchanges, though antiferromagnetic exchange dominates over ferromagnetic coupling in the low-temperature region.
Co-reporter:Javeed Ahmad Sheikh, Amit Adhikary and Sanjit Konar
New Journal of Chemistry 2014 vol. 38(Issue 7) pp:3006-3014
Publication Date(Web):09 Apr 2014
DOI:10.1039/C4NJ00349G
Three new Ln3+ coordination compounds having formulae, [Gd4(μ3-OH)2(L)2L1L2(HOCH3)2]·11H2O (1), [Dy4(μ3-OH)2(L)2L1L2(H2O)2]·11H2O (2) and [Dy4(μ4-O)(OMe)(HOMe)2(CH3COO)3(L3)2]·2H2O (3), have been synthesized in a one pot synthesis from O-vanillin, diaminomaleonitrile (DAMN), LnCl3·6H2O (Ln = Gd3+, Dy3+) and sodium acetate for 3, {H2L = 2,3-bis((E)-(2-hydroxy-3-methoxy benzylidene) amino)maleonitrile, HL1 = (2-amino-3-((E)-(2-hydroxy-3-methoxy benzylidene)amino)maleonitrile), H3L2 = ((1E,3Z,8Z,10E)-1,6,11-tris(2-hydroxy-3-methoxyphenyl)-2,5,7,10-tetraazaundeca-1,3,8,10-tetraene-3,4,8,9-tetracarbonitrile) and H2L3 = 2-((cyano(2-hydroxy-3-methoxyphenyl)methyl)amino)-3-((E)-(2-hydroxy-3-methoxybenzylidene)amino)maleonitrile. Single-crystal X-ray diffraction studies reveal that compounds 1 and 2 are quasi-isostructural, exhibiting tetranuclear hemicubane-like cores. For 3 the metal centers are arranged in a tetrahedral arrangement. Complexes 1–3 were formed with the ligands (L1–L3), which resulted in situ during synthesis. Magnetic studies reveal that compound 1 shows significant magnetocaloric effect (ΔSm = −27.2 J kg−1 K−1) at 3 K and 7 T. The magnetic properties of 2 and 3 are considerably different. Indeed, no out-of-phase alternating current (ac) signal is noticed for 2, whereas 3 shows a slow relaxation of magnetization. These differences are most likely due to the different Dy–O–Dy angles observed for the respective cores.
Co-reporter:Amit Adhikary, Javeed Ahmad Sheikh, Anita Dutt Konar and Sanjit Konar
RSC Advances 2014 vol. 4(Issue 24) pp:12408-12414
Publication Date(Web):20 Jan 2014
DOI:10.1039/C3RA45928D
This report describes the synthesis and characterization of three different complexes of molecular formulae {[Cu6L2(ClO4)4(μ-ClO4)2(H2O)9](ClO4)2·8H2O}n(1), [Cu6L2Cl6(μ2-Cl)2(H2O)2]·3H2O (2) and [Cu9L6](ClO4)6·6H2O·2CH3CN·CH3OH (3), where, H2L = bis[(2-pyridyl)methylene] pyridine 2,6 dicarbohydrazone. X-ray crystallography reveals that complex 1 exhibits 1D chain, complex 2 is a hexanuclear entity and an unsymmetrical [3 × 3] grid formation in complex 3. Variable temperature magnetic measurements were performed, they show that weak antiferromagnetic interactions exist among the metal centers in complex 1 and both ferro- and antiferromagnetic interactions coexist for complexes 2 and 3. Below 20 K antiferromagnetic interactions dominate for complex 2 whereas it is ferromagnetic for complex 3. Transformation from one cage to another is possible at mild reaction conditions, which results in a dramatic change in the magnetic properties.
Co-reporter:Amit Adhikary;Dr. Himanshu Sekhar Jena;Sajal Khatua ;Dr. Sanjit Konar
Chemistry – An Asian Journal 2014 Volume 9( Issue 4) pp:1083-1090
Publication Date(Web):
DOI:10.1002/asia.201301619
Abstract
Two unique lanthanide-based cages [Ln10(L)5(μ2-OH)6(H2O)22](Cl)4⋅7 H2O ([Gd10] and [Dy10]) have been synthesized by using a hydrazone-based ligand H4L (H4L=2,6-bis[(3-methoxysalicylidene)hydrazinecarbonyl]pyridine) and LnCl3⋅x H2O. Structural characterization of [Gd10] reveals an aesthetically pleasing self-assembly of five L4− and ten Gd3+ ions forming a 2×[1×5] rectangular array. The ladder-shaped cage consists of three “rungs” and two “rails” that are occupied by five ligands. Six out of ten gadolinium centers act as rung locks. Further analysis revealed that three chloride ions are encapsulated inside each discrete [Gd10] molecule through hydrogen bonding and other noncovalent interactions. Both the complexes ([Gd10] and [Dy10]) were characterized by powder X-ray diffraction and thermogravimetric analysis, which shows that they are isostructural in nature. Magnetic investigations reveal that [Gd10] is a good candidate for magnetic refrigeration with a significant entropy change (−ΔSm) of 37.4 J kg−1 K−1 for an applied field of 7 T and at 3 K. Whereas [Dy10] shows single-molecule-magnet-like behavior.
Co-reporter:Javeed Ahmad Sheikh, Soumyabrata Goswami, Amit Adhikary, and Sanjit Konar
Inorganic Chemistry 2013 Volume 52(Issue 8) pp:4127-4129
Publication Date(Web):April 3, 2013
DOI:10.1021/ic3025183
This report describes the synthesis, characterization, and magnetic properties of two novel phosphonate-based CoII cages. Structural investigation reveals some interesting geometrical features in the molecular core that may provide new models in single molecular magnetic materials.
Co-reporter:Javeed Ahmad Sheikh, Himanshu Sekhar Jena, Amit Adhikary, Sajal Khatua, and Sanjit Konar
Inorganic Chemistry 2013 Volume 52(Issue 17) pp:9717-9719
Publication Date(Web):August 14, 2013
DOI:10.1021/ic401754q
A novel octadecanuclear copper pyrazolate–phosphonate nanocage with a bowl-shaped arrangement of the copper(II) centers in the asymmetric unit is reported. Characterization of intermediates in both solid and solution states aids to propose the mechanism of such a giant aggregation. Magnetic studies affirm the presence of antiferromagnetic interactions between the adjacent copper(II) centers. Extensive supramolecular interactions result in a framework structure.
Co-reporter:Soumyabrata Goswami ; Amit Adhikary ; Himanshu Sekhar Jena ; Soumava Biswas
Inorganic Chemistry 2013 Volume 52(Issue 20) pp:12064-12069
Publication Date(Web):October 1, 2013
DOI:10.1021/ic401886f
The reaction of dilithium squarate with Fe(II) perchlorate led to the formation of a new Fe(II)-based 3D MOF, [Fe3(OH)3(C4O4)(C4O4)0.5]n (1), with homoleptic squashed cuboctahedral cages. Complex 1 crystallizes in the monoclinic C2/c space group. Fe(II) centers in the complex are octahedrally coordinated by four squarate dianions in axial and equatorial positions and two hydroxyl groups in the remaining equatorial positions. The interesting structural feature of 1 is that the three-dimensional framework is an infinite extension of nanoscopic cuboctahedral cages. The framework also contains two types of voids; the larger hydrophobic ones are surrounded by aromatic squarate ligands, while the smaller ones are hydrophilic with hydroxyl groups on the surface connected by bifurcated hydrogen bonding interaction. A variable temperature magnetic study shows spin-canted long-range antiferromagnetic ordering in the low temperature regime.
Co-reporter:Suresh Sanda ; Srinivasulu Parshamoni
Inorganic Chemistry 2013 Volume 52(Issue 22) pp:12866-12868
Publication Date(Web):October 30, 2013
DOI:10.1021/ic402095u
A new 2D interdigitated and highly flexible, breathing metal–organic framework has been synthesized through a diffusion technique by using the aldrithiol linker and pyromellitate ligand. The compound shows selective, stepwise, reversible, and hysteretic adsorption properties for CO2 gas and H2O, MeOH, and CH3CN vapors.
Co-reporter:Suresh Sanda, Srinivasulu Parshamoni, Amit Adhikary, and Sanjit Konar
Crystal Growth & Design 2013 Volume 13(Issue 12) pp:5442-5449
Publication Date(Web):November 1, 2013
DOI:10.1021/cg401403a
Four new two-dimensional/three-dimensional (2D/3D) bpmh-based metal organic frameworks, namely, {[Zn(1,3-adaa)(bpmh)]}n (1), {[Cd(1,3-adaa)(bpmh)]}n (2), {[Zn(1,4-pdaa)(bpmh)]}n (3), and {[Co(1,4-pdaa)(bpmh)]}n (4) (bpmh = N,N-bis-pyridin-4-ylmethylene-hydrazine, 1,3-adaa = 1,3-adamantane diacetic acid, 1,4-pdaa = 1,4-phenylene diacetic acid) have been synthesized through the slow diffusion technique. Structural determination reveals that compounds 1 and 2 have 2D layered architectures with similar framework topology, whereas 3 and 4 are isostuctural 3D frameworks. Both 1 and 2 perceives a common secondary building unit (SBU) [M2(adaa)4(bpmh)4] [M = Zn(1) and Cd(2)]. In compound 1, 1,3-adaa exhibits both μ- 1,1 and μ- 1,2 bridging modes, whereas in 2 it shows both μ-1,1 and μ-1,1,2 bridging modes. The difference in the bridging mode of 1,3-adaa in 1 (Zn) and 2 (Cd) is responsible for the shorter M···M contacts in 2 (3.872 Å) than in 1 (4.13 Å) in the SBU. The 1,3-adaa ligands are sandwiched between the bpmh linkers in compounds 1 and 2. In compounds 3 and 4, 1,4-pdaa exhibits both μ-1 and μ-1,1 bridging modes and are isostructural in nature. The metal centers are arranged in a helical fashion around 21 screw axis in 3 and 4. In compounds 1–4, the used dicarboxylic acids act as pillars between the metal-bpmh layers. Solid-state photoluminescent properties of compounds 1–3 show ligand (n → π* and π → π*)-based florescence. The magnetic studies of compound 4 show presence of the antiferromagnetic exchange between the metal centers.
Co-reporter:Soumyabrata Goswami, Amit Adhikary, Himanshu Sekhar Jena and Sanjit Konar
Dalton Transactions 2013 vol. 42(Issue 27) pp:9813-9817
Publication Date(Web):13 May 2013
DOI:10.1039/C3DT51195B
Three lanthanide one-dimensional coordination polymers, obtained using Ln3+ salts and croconate dianion, were structurally characterized. Magnetic studies reveal that the gadolinium analogue exhibits a large magnetocaloric effect while single-molecule magnet behaviour is observed in the dysprosium analogue.
Co-reporter:Soumava Biswas, Amit Adhikary, Soumyabrata Goswami and Sanjit Konar
Dalton Transactions 2013 vol. 42(Issue 37) pp:13331-13334
Publication Date(Web):15 Jul 2013
DOI:10.1039/C3DT51668G
A new 2D Gd(III)-based coordination polymer has close to the highest cryogenic magnetocaloric effect of any MOF reported so far. The experimental results reveal its structural features and magnetic properties.
Co-reporter:Sajal Khatua, Soumyabrata Goswami, Srinivasulu Parshamoni, Himanshu Sekhar Jena and Sanjit Konar
RSC Advances 2013 vol. 3(Issue 47) pp:25237-25242
Publication Date(Web):25 Sep 2013
DOI:10.1039/C3RA44331K
A 2D MOF with the secondary building unit [Co3(CTC)6(Py)2(OH)2] is synthesized using the sodium salt of a flexible ligand, cis,cis-cyclohexane-1,3,5-tricarboxylate (Na-CTC), and a cobalt trimer ([Co3O(CH3COO)6(Py)3]·ClO4). Structural analysis shows that the complex crystallizes in the monoclinic space group P21/n and forms a 2D framework with channel sizes of 9.0 × 4.2 Å2. Magnetic characterization shows spin-canting ferromagnetic behaviour at low temperatures. Frequency dependency for in-phase (χ′M) and out-of-phase (χ′′M) signals at low temperatures is observed from the AC measurements. The gas adsorption behaviour suggests selectivity towards CO2 over N2, and demonstrates enhancement of CO2 uptake (19–33 cm3 g−1) on lowering the temperature (273–195 K).
Co-reporter:Amit Adhikary, Himanshu Sekhar Jena and Sanjit Konar
Dalton Transactions 2015 - vol. 44(Issue 35) pp:NaN15543-15543
Publication Date(Web):2015/07/24
DOI:10.1039/C5DT01569C
Herein, the synthesis, structural characterization, magnetic properties and guest binding activities of four Fe3+ based double-stranded helicates namely; [Fe2(L)2](ClO4)(Cl)·4(CH3OH)·2(H2O) (1), [Fe2(L)2](BF4)2·2(H2O) (2), [Fe2(L)2](NO3)2·3(CH3OH)·2(H2O) (3), and [Fe2(L)2](Cl)2·2(CH3OH)·4(H2O) (4) are reported. Complexes 1–4 have been synthesized using the hydrazide-based ligand H2L (H2L = N′1,N′4-bis(2-hydroxybenzylidene)succinohydrazide) and the corresponding Fe2+ salts. Each of the independent cationic complexes [Fe2(L)2]2+ shows double-stranded helicates from the self-assembly of the ligand and metal ions in a 2:2 ratio, where the individual Fe3+ centre is lying on a C2-axis and the ligand strands wrap around it. In 1–4, ligand L adopts “pseudo-C” conformations and forms a double-stranded dinuclear helicate with a small cage in between them. Moreover, in 1–4, each of the independent cationic complexes [Fe2L2]2+ is inherently chiral and possesses P for right-hand and M for left-hand helicity and as a consequence is a racemic solid. Detailed magnetic studies of all the complexes reveal that the Fe3+ centres are magnetically isolated and isotropic in nature. Estimation of the Magnetocaloric Effect (MCE) from magnetization data unveils a moderate MCE at a temperature of 3 K with magnetic entropy changes (−ΔSm) of 22.9, 27.7, 24.1, 26.5 J kg−1 K−1 at a magnetic field of 7 T for complexes 1–4, respectively. Also, the variation of the −ΔSm values was justified by considering the parameter of magnetization per unit mass. Stability of all the complexes in solution phase was confirmed by ESI-mass spectrometric analysis and liquid phase FT-IR spectroscopy. Further, the interaction of the complexes 1–4 with Rhodamine B dye was examined by UV-vis and fluorescence spectroscopic study. The observed blue-shift in the fluorescence study and hyperchromicity and hypochromicity with the appearance of two isosbestic points in the UV-vis study ascertain the interactions of the dye with the complexes. A DNA binding study by absorption spectral titration suggests the weak external intercalation of complex 1 within the nucleotide of calf thymus DNA. Computational study supports the isotropic nature of the metal centres and the consequent high spin multiplicity, which assists the complexes to show significant magnetic entropy changes.
Co-reporter:Soumyabrata Goswami, Soumava Biswas and Sanjit Konar
Dalton Transactions 2015 - vol. 44(Issue 9) pp:NaN3953-3953
Publication Date(Web):2015/01/22
DOI:10.1039/C4DT03575E
Two unprecedented oxonate based 1D coordination polymers with FeII and CoII have been synthesized. A detailed magnetic investigation revealed that these complexes are the first oxonate based systems to exhibit spin canted antiferromagnetic ordering at low temperatures. Proton conductivity studies of the complexes showed good proton conduction ability at elevated temperatures and under high humidity conditions.
Co-reporter:Upendarrao Golla, Amit Adhikary, Amit Kumar Mondal, Raghuvir Singh Tomar and Sanjit Konar
Dalton Transactions 2016 - vol. 45(Issue 29) pp:NaN11863-11863
Publication Date(Web):2016/06/23
DOI:10.1039/C6DT01496H
Four coordination compounds of formulae [CuII2(H2L1)(HL1)](ClO4)3·H2O (1), [CuII2(H2L2)(CH3OH)2](ClO4)2·2CH3OH (2), [CoII2(H2L1)2](ClO4)4 (3) and [CoII2(H2L2)2]·2H2O (4) were synthesized via self-assembly of succinohydrazone derived ligands (H2L1 = N′,N′-4-bis(2-pyridyl)succinohydrazide, H4L2 = N′,N′-4-bis(2-hydroxybenzylidene)succinohydrazide) and Cu2+ and Co2+ ions, respectively. The compounds were characterized by crystal structure determination, magnetic measurements and biological activities. Compounds 1, 3 and 4 have discrete double helicate structures, whereas compound 2 is a one-dimensional chain. Magnetic studies show antiferromagnetic exchange interactions in 2 with a J value of −67.1 cm−1 and antiferromagnetic spin-canting in compound 3 originates through supramolecular H-bonding. For compound 3, a clear bifurcation was observed in zero field cooled (ZFC) and field cooled (FC) measurement at a temperature of 3.5 K and field of 0.1 T, implying long range magnetic ordering below this temperature. Interestingly, all of compounds 1–4 show significant changes in their absorption (hypo- and hyperchromism) in the presence of SS-DNA, inferring interaction between the compounds and DNA. In addition, compounds 1–4 significantly exhibited nuclease activities on both RNA and pUC19 plasmid DNA. Moreover, the nuclease activity was further enhanced in the presence of oxidant (H2O2) and suggests the possible role of reactive oxygen species in DNA nicking ability of compounds 1–4. Furthermore, compounds 1, 2 and 4 exhibited significant cytotoxicity against mammalian cancer cell lines (HeLa, A549 and MDAMB-231). In addition, our results from Annexin/PI staining and DNA fragmentation assays revealed that these compounds are capable of inducing apoptosis and have potential to act as anticancer drugs.
Co-reporter:Amit Adhikary, Javeed Ahmad Sheikh, Soumava Biswas and Sanjit Konar
Dalton Transactions 2014 - vol. 43(Issue 24) pp:NaN9343-9343
Publication Date(Web):2014/03/25
DOI:10.1039/C4DT00540F
The synthesis, crystal structure and magnetic properties of four polynuclear lanthanide coordination complexes having molecular formulae, [Gd3L12(H2O)8(Cl)](Cl)4·10H2O (1), [Dy3L12(H2O)9](Cl)5·6H2O (2) [Gd6L22(HCO2)4(μ3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (3) and [Dy6L22(HCO2)4(μ3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (4) (where H2L1 = bis[(2-pyridyl)methylene]pyridine-2,6-dicarbohydrazide and H4L2 = bis[2-hydroxy-benzylidene]pyridine-2,6-dicarbohydrazide) are reported. Structural investigation by X-ray crystallography reveals similar structural features for complexes 1 and 2 and they exhibit butterfly like shapes of the molecules. Non-covalent interactions between the molecules create double helical arrangements for both molecules. Complexes 3 and 4 are isostructural and the core structures feature four distorted hemi-cubanes connected by vertex sharing. Magnetic studies unveil significant magnetic entropy changes for complexes 1, 3 and slow relaxation of magnetization for both dysprosium analogues 2 and 4.
Co-reporter:Prasath Rangaraj, Srinivasulu Parshamoni and Sanjit Konar
Chemical Communications 2015 - vol. 51(Issue 85) pp:NaN15529-15529
Publication Date(Web):2015/08/28
DOI:10.1039/C5CC06311F
In a new concept, an iodine loaded amine functionalized MOF was employed as a syringe pump for the slow release of iodine as a catalyst in the synthesis of thienyl dipyrromethanes under ambient conditions and turned out to be successful. The catalytic activities were compared with an isoreticular non-functionalized MOF and other conventional catalysts.
Co-reporter:Soumyabrata Goswami, Amit Adhikary, Himanshu Sekhar Jena and Sanjit Konar
Dalton Transactions 2013 - vol. 42(Issue 27) pp:NaN9817-9817
Publication Date(Web):2013/05/13
DOI:10.1039/C3DT51195B
Three lanthanide one-dimensional coordination polymers, obtained using Ln3+ salts and croconate dianion, were structurally characterized. Magnetic studies reveal that the gadolinium analogue exhibits a large magnetocaloric effect while single-molecule magnet behaviour is observed in the dysprosium analogue.
Co-reporter:Soumava Biswas, Amit Adhikary, Soumyabrata Goswami and Sanjit Konar
Dalton Transactions 2013 - vol. 42(Issue 37) pp:NaN13334-13334
Publication Date(Web):2013/07/15
DOI:10.1039/C3DT51668G
A new 2D Gd(III)-based coordination polymer has close to the highest cryogenic magnetocaloric effect of any MOF reported so far. The experimental results reveal its structural features and magnetic properties.
Co-reporter:Amit Kumar Mondal, Jesús Jover, Eliseo Ruiz and Sanjit Konar
Chemical Communications 2017 - vol. 53(Issue 38) pp:NaN5341-5341
Publication Date(Web):2017/04/18
DOI:10.1039/C7CC02584J
In this work we report two pentacoordinated CoII–P4X1 Single Ion Magnets (SIMs) based on P-donor ligands. The tetradentate ligand tris[2-(diphenylphosphino)ethyl]phosphine allows the obtention of the isostructural square pyramidal [Co(PP3)Cl]·ClO4 (1) and [Co(PP3)Br]·ClO4 (2) complexes. Consistent theoretical and experimental studies indicate that these complexes have a high spin (S = 3/2) ground state and suggest that the relaxation dynamics is governed by ground state quantum tunneling, whereas its temperature dependence is directed by optical or acoustic Raman processes.
Co-reporter:Amit Kumar Mondal, Vijay Singh Parmar, Soumava Biswas and Sanjit Konar
Dalton Transactions 2016 - vol. 45(Issue 11) pp:NaN4557-4557
Publication Date(Web):2016/01/25
DOI:10.1039/C5DT04173B
A rare class of dinuclear double-stranded helicates having tetrahedral metal centres with formulae [Co2(L1)2]·2(CH3CN) (1), [Co2(L2)2]·6(CH3CN) (2), [Zn2(L1)2]·2(CH3CN)·(CH3OH) (3) and [Zn2(L2)2]·4(CH3CN) (4) were synthesized and characterized. Detailed dc and ac magnetic susceptibility measurements reveal the presence of field induced slow magnetic relaxation behaviour in high spin tetrahedral CoII centres with an easy-plane magnetic anisotropy. Complexes 1 and 2 are the rare examples of transition metal based helicates showing such behaviour. Furthermore, 3 and 4 exhibit fluorescence emission in different solvents that are analyzed in terms of fluorescence quantum yields and lifetimes.
Co-reporter:Amit Kumar Mondal, Soumyabrata Goswami and Sanjit Konar
Dalton Transactions 2015 - vol. 44(Issue 11) pp:NaN5094-5094
Publication Date(Web):2015/01/30
DOI:10.1039/C4DT03620D
The reaction of 2,6-bis(1-salicyloylhydrazonoethyl)pyridine [H4daps] with Dy(NO3)3·5H2O led to the formation of two new Dy(III) based complexes with formulae [Dy(H4daps)(H2O)3(NO3)] (NO3)2 (H2O) (1) and [Dy(H3daps)(H2O)2(NO3)] (NO3) (MeOH) (2). Complexes 1 and 2 were characterized by crystal structure determination, magnetic measurements and photoluminescence studies. In comparison with complex 1, complex 2 shows a slight difference of local symmetry around the Dy(III) center which is attributed to deprotonation of the ligand and also to different binding modes of the peripheral NO3− anion. AC magnetic susceptibility measurements reveal that both complexes exhibit single-molecule magnet (SMM) behavior, with the thermal energy barrier of 1 being higher than that of 2 (Ueff = 32.7 K for 1 and 23.8 K for 2). Our investigation discloses that small differences in the coordination environment around the metal centre played an important role in the difference in relaxation dynamics of the complexes. Solid state photoluminescence studies showed their photoluminescence behaviour with quantum yields of 0.98 and 1.44%.
Co-reporter:Suresh Sanda, Srinivasulu Parshamoni, Soumava Biswas and Sanjit Konar
Chemical Communications 2015 - vol. 51(Issue 30) pp:NaN6579-6579
Publication Date(Web):2015/03/04
DOI:10.1039/C4CC10442K
A Zn(II) based luminescent metal organic framework is synthesized, which acts as a dual functional fluorescent sensor to selectively detect picric acid and palladium(II).
Co-reporter:Himanshu Sekhar Jena, Soumyabrata Goswami, Suresh Sanda, Srinivasulu Parshamoni, Soumava Biswas and Sanjit Konar
Dalton Transactions 2014 - vol. 43(Issue 45) pp:NaN16999-16999
Publication Date(Web):2014/10/16
DOI:10.1039/C4DT02496F
We present a robust two dimensional coordination polymer, [Ni2(L)2(N(CN)2)2]n (1) (LH = 2-((1-(pyridin-2-yl)ethylimino)methyl)phenol; N(CN)2− = dicyanamide ion) using a chiral Schiff base (LH), which shows diastereoselectivity in the structure via a chiral self-discrimination process, ferro- and antiferromagnetic interactions among the metal centers and unusual CO2 uptake behavior as a porous framework
Co-reporter:Srinivasulu Parshamoni, Suresh Sanda, Himanshu Sekhar Jena and Sanjit Konar
Dalton Transactions 2014 - vol. 43(Issue 19) pp:NaN7199-7199
Publication Date(Web):2014/02/14
DOI:10.1039/C4DT00228H
A new 2D pillared-bilayer flexible open metal organic framework {[Cu(tdc)(bpe)]n·2n(H2O)·n(MeOH)} (compound 1) [H2tdc = 2,5 thiophenedicarboxylic acid; bpe = 1,2-bis(4-pyridyl)ethane] has been synthesized through a solvent diffusion technique and structurally characterized. The structure analysis reveals that the tdc ligands formed bilayers with the Cu(II) ions along the b-direction and the layers are further pillared by bpe linkers and resulted in a 2D pillared-bilayer porous framework with a four connected uninodal sq1/Shubnikob tetragonal plane net with the Schälfli symbol {44·62}. The framework is enclosed with large square shaped channels (13.7 × 8.35 Å2) along the bc-plane and the channels are occupied by guest solvent molecules. The adsorption studies reveal that compound 1 shows selective adsorption for CO2 over CH4 at room temperature and it also shows hysteretic sorption for a few protic solvents (H2O and EtOH) and a Type-1 isotherm for an aprotic solvent (CH3CN). The catalytic performance of compound 1 for Glaser type homo-coupling reactions has also been reported.
Co-reporter:Srinivasulu Parshamoni, Himanshu Sekhar Jena, Suresh Sanda and Sanjit Konar
Inorganic Chemistry Frontiers 2014 - vol. 1(Issue 8) pp:NaN620-620
Publication Date(Web):2014/07/14
DOI:10.1039/C4QI00077C
Three hydrogen bonded three-dimensional (3D) metal–organic frameworks (MOFs) namely [Cd(L-tart)(bpy)(H2O)]n·9n(H2O) (1), [Cd(D-tart)(bpy)(H2O)]n·9n(H2O) (2) and [Cd(DL-tart)(bpy)(H2O)]n·6n(H2O) (3) (tart = tartaric acid, bpy = 4,4-bipyridine) have been synthesized by the solvent diffusion technique at room temperature. Compounds 1 and 2 have been characterized by single crystal X-ray analysis, whereas the powder X-ray diffraction patterns show that the structural integrity of compound 3 is similar to 1 and 2. Structural analysis of 1 and 2 shows H-bonded homochiral 3D MOFs, fabricated by the hydrogen bonding interactions between the nearby 2D pillared-layer frameworks through the metal-bound water, metal-bound carboxylate, free carboxylic acid and the hydroxy group of L-/D- tart. The absolute configuration of all the compounds was investigated by solid state circular dichroism (CD) spectroscopy, which signifies that 1 and 2 are enantiomers whereas 3 is racemic. The adsorption studies reveal that compounds 1–3 show a significant amount of uptake for water vapor (∼239 mL g−1 for 1, ∼240 mL g−1 in 2, whereas 184 mL g−1 for 3 at P/P0 ≈ 1 bar) over other solvents (MeOH, EtOH) and an impedance measurement indicates that these compounds show proton conduction (1.3 × 10−6 S cm−1 in 1, 1.3 × 10−6 S cm−1 in 2 and 4.5 × 10−7 S cm−1 in 3) at a higher temperature (358 K) and at 95% relative humidity. The observed conductivity is explained by the so-called vehicle mechanism (activation energy (Ea) = 0.63–0.77 eV). Since all the compounds contain H3O+ cations in the interlayer space, the hydronium ions might act as vehicles to transport the protons in the interlayer space. The photoluminescence properties of all the compounds are also reported.
Co-reporter:Javeed Ahmad Sheikh, Soumyabrata Goswami and Sanjit Konar
Dalton Transactions 2014 - vol. 43(Issue 39) pp:NaN14585-14585
Publication Date(Web):2014/07/30
DOI:10.1039/C4DT01791A
Two types of heterometallic aggregates of the general formula [(CoII)3(CoIII)2Ln3(μ3-OH)5(O2CtBu)12(L)2]·2H2O (Ln = GdIII (1), DyIII (2)) and [(CoIII)3Ln3(μ3-OH)4(O2CtBu)6(L)3](NO3)2·2CH3CN·2H2O (Ln = GdIII (3), DyIII (4)) were successfully isolated in reactions with [Co2(μ-OH2)(O2CtBu)4]·(HO2CtBu)4, Ln(NO3)3 and n-N-butyldiethanolamine (H2L) under ambient conditions by a change in the stoichiometry of the reactants from 1:1:1 to 1:1:2 in order. Bond Valence Sum (BVS) calculations and bond lengths indicate the presence of mixed valent Co (CoII, CoIII) centres in compounds 1 and 2 and only CoIII centres in 3 and 4 as required for the charge balances and supported by the magnetic measurements. Isostructural crab shaped complexes 1 and 2 feature distorted cubane cores that edge share to each other whereas the metallic core of 3 or 4 displays hemicubane like arrangement of metal centres and oxygen atoms. Overall structural symmetry was found to enhance on moving from the former to the latter series of complexes. Magnetic studies reveal significant magnetic entropy changes for complexes 1 and 3 (−ΔSm = 21.57 and 19.39 J kg−1 K−1) and single molecular magnetic behaviour for 2 and 4.
Co-reporter:Soumyabrata Goswami, Amit Kumar Mondal and Sanjit Konar
Inorganic Chemistry Frontiers 2015 - vol. 2(Issue 8) pp:NaN712-712
Publication Date(Web):2015/06/16
DOI:10.1039/C5QI00059A
Nanoscopic molecular magnets have attracted tremendous interest in recent years both from an experimental and a theoretical point of view because of their potential application in magnetic data storage devices, quantum computing and molecular spintronics. These molecules have crucial advantages over magnetic nanoparticles in terms of their perfectly mono-dispersed phase, chemical flexibility and high purity. This review discusses a few basic concepts that are needed to understand the magnetic properties observed in nanoscopic molecular magnets, a chemical approach for their synthesis and magneto-structural correlations. It includes a few selected examples and discusses the new trends in the field.
