•Covalent attachment of multiple DNA strands to a single porphyrin molecule•Construction of DNA-porphyrin nanonetwork by hybridization mediated self-assembly process•High ROS generation efficiency and light sustainability of porphyrins in DNA-porphyrin observed•High killing efficiency of gram-positive S. aureus following light irradiation of DNA-porphyrin networkDNA derived well-controlled arrangement of porphyrins has emerged as promising hybrid nanostructures. Exceptional biocompatibility and DNA-directed surface addressability coupled with rich symmetry features of the porphyrin have made these hybrid nanostructures attractive candidates for potential biomedical and biotechnological applications. However, the noteworthy photophysical properties of porphyrin and related molecules when present in DNA based nanostructures are yet to be explored fully and should be a matter of intense research that may unearth a plethora of interesting applications of these nanostructures. Herein, we demonstrate the construction of novel self-assembled DNA-porphyrin hybrid nanonetworks that utilize the porphyrin core for antibacterial applications. Porphyrin derivative with four pendant NH2 groups was synthesized and conjugated with the 5′-PO4 of ss-DNA by solution phase phosphoramidation coupling reaction. The conjugation was followed by DNA hybridization mediated self-assembly to form DNA-porphyrin hybrid nanonetwork. The enhanced antimicrobial property of the nanonetwork was envisioned following light irradiation at relevant wavelength. In line with this, comparative antimicrobial activities against gram-negative (Escherichia coli BL-21) and gram-positive bacteria (Staphylococcus aureus) have been studied. Interestingly, DNA-porphyrin nanonetwork afforded highly efficient and coherent photoinduced reactive oxygen species (ROS) generation to display antimicrobial activity against Staphylococcus aureus. The escalated and coherent ROS generation from the nanonetworks was attributed to the ordered placement of the porphyrins that inhibits self-quenching. Our work points out to a good alternative for antibiotic free strategies for preservation of biological materials and other applications.Download high-res image (141KB)Download full-size image

The synthesis and characterization of a new pyrazine-based “flexible” and ditopic platinum(II) organometallic molecule (3) is being reported. Flexibility in this molecule is due to the presence of ether functional groups that bridge the rigid core and periphery. Due to the presence of square planar Pt(II) centers at the two ends, the molecule's potential to act as an acceptor building block in the construction of metallamacrocycles was tested. Upon reaction of 3 with various dicarboxylates in a 1 : 1 stoichiometric ratio, [2 + 2] self-assembled neutral metallacycles (M1–M3) were obtained in high yields. M1–M3 were characterized using multinuclear NMR, high resolution mass spectrometry and elemental analyses. The shape and dimensions of these supramolecular structures were also confirmed by optimizing the geometry using the density functional theory (DFT) approach. Computational studies suggest that M1–M3 are nanoscalar macrocyles. Furthermore, using isothermal titration calorimetry (ITC), it was shown that 3 can bind with picric acid (PA) to yield a 3·(PA)2 host–guest complex. The magnitude of the binding constant indicates that 3 has significant affinity for PA.

Coordination of a triptycene-based ditopic Schiff base ligand (H2L) with Zn2+ leads to the formation of a novel trinuclear circular species. A combination of 1H NMR spectroscopy, infrared spectroscopy, mass spectrometry and elemental analysis allow the unambiguous characterization of H2L and Zn3L3·8H2O. DFT molecular modelling has been used to study the possible isomers of the cyclic trinuclear Zn(II) complex that results from the combination of conformational and optical isomers of the ligand. A NOESY experiment demonstrated that in the trinuclear circular zinc(II) helicate the three isomers of the ligand have an anti configuration of N,O-donor domains and an s-cis configuration of their imine bonds. Besides, a UV-VIS absorption and fluorescence emission study of H2L and Zn3L3·8H2O has been performed.

Two new supramolecular building blocks derived from pyrazine are introduced. These molecules, having pendant pyridine units covalently linked to central pyrazine ring, are structurally rigid with pre-defined bite angles. Therefore they can act as donor tectons in design of supramolecular hexagons using coordination driven self-assembly protocol. Multinuclear NMR (including 1H DOSY) and mass spectrometry have been utilized to confirm the purity and stoichiometry of these self assembled hexagonal ensembles. PM6 molecular modeling studies corroborate their hexagonal shape and nanoscalar dimensions.

Herein, facile synthesis and characterization of four triazole linked network polymers (TNPs) in high yields is described. These nitrogen rich polymers are derived using a “click” reaction between 2,6,14-triazido triptycene and various di- or triethynyl comonomers. The TNPs are microporous and exhibit high surface area (SABET up to 1348 m2 g−1). Due to the incorporation of the 1,2,3-triazole motif (a CO2-philic moiety), the TNPs record moderate to high CO2 uptake (up to 4.45 mmol g−1 at 273 K and 1 bar). The TNPs also show very good CO2/N2 (up to 48) and CO2/CH4 (8–9) selectivity. While the highest storage capacity has been registered by TNP4 (CO2 4.45 mmol g−1 at 273 K and 1 bar, CH4 23.8 mg g−1, H2 1.8 wt%), the highest CO2/N2 and CO2/CH4 selectivity is shown by TNP3 which contains additional nitrogen rich building blocks in the form of heteroaromatic pyrazine rings. These results suggest that TNPs are porous materials with potential practical application in gas storage and separation.

The design, synthesis, and characterization of a new pyrazine-based ditopic platinum(II) organometallic complex are reported. The molecular structure of the organoplatinum pyrazine dipod was determined by single-crystal X-ray crystallography. The potential utility of this organometallic ditopic acceptor as a building block in the construction of neutral metallasupramolecular macrocycles containing the pyrazine motif was explored. Pyrazine motifs containing supramolecules were characterized by multinuclear NMR (including 1H DOSY), mass spectrometry, and elemental analysis. The geometry of each supramolecular framework was optimized by employing the PM6 semiempirical molecular orbital method to predict its shape and size. The ability of the pyrazine-based organoplatinum complex to act as a host for nitroaromatic guest (2,4-dinitrotoluene and PA) molecules was explored by isothermal titration calorimetry (ITC). The binding stoichiometry and thermodynamic parameters of these host–guest complexation reactions were evaluated using ITC. Theoretical calculations were performed to obtain insight into the binding pattern between the organometallic host and nitroaromatic guests. The preferable binding propensity of the binding sites of complex 1 for both nitroaromatics (PA and 2,4-dinitrotoluene) determined by molecular simulation studies corroborates well with the experimental results as obtained by ITC experiments.

The synthesis and characterization of cationic two-dimensional metallamacrocycles having a hexagonal shape and cavity are described. Both macrocycles utilize a pyrazine motif containing an organometallic acceptor tecton with platinum(II) centers along with different donor ligands. While one macrocycle is a relatively larger [6 + 6], the other is a relatively smaller [2 + 2] polygon. A unique feature of the smaller ensemble is that it is an irregular polygon in which all six edges are not of equal length. Molecular modeling of these macrocycles confirmed the presence of hexagonal cavities. The ability of these π-electron rich macrocycles to act as potential hosts for relatively electron deficient nitroaromatics (DNT = 2,4-dinitrotoluene and PA = picric acid) has been studied using isothermal titration calorimetry (ITC) as a tool. Molecular dynamics simulation studies were subsequently performed to gain critical insight into the binding interactions between the nitroaromatic guest molecules (PA/DNT) and the ionic macrocycles reported herein.

•Synthesis of 2,6-diazidotriptycene: a new building block in triptycene polymer chemistry.•Polytriazole synthesis using Cu(I)OAc catalyzed “Click” reaction.•Temperature dependent regioselective incorporation of 1,2,3-triazole motif.•Strong host-guest interaction between polytriazole polymers and nitroaromatics.We report facile synthesis of a new triptycene based monomeric building block 2,6-diazidotriptycene (DAZT) that has been utilized to synthesize a series of triptycene based and triazole linked alternate co-polymer (TPT1-TPT4) via Cu(I)OAc catalyzed Sharpless “Click reaction”. The effect of reaction temperature on regioselective incorporation of 1,2,3-triazole motif in the polymer backbone has been studied. The newly synthesized triptycene-polytriazole (TPT) polymers (having 1,4-regioregular 1,2,3-triazole units) have been characterized using NMR, FTIR, and UV–vis spectroscopic techniques. Interestingly, TPTs possess moderately high molecular weight, are organosoluble, amorphous in nature and have reasonably high thermal stability with Tg > 400 °C. Additionally, selected polymers are fluorescent in nature. These fluorescent TPTs interact strongly with nitroaromatics (NACs), as evident from the binding constants values obtained from Benesi−Hildebrand fluorescence plots (assuming complexation 1:1). The extent of fluorescence quenching of these TPTs in presence of NACs was also estimated from Stern–Volmer (SV) plots. It was observed that polymer backbone which is richer in nitrogen, exhibited superior sensitivity towards NACs. Amongst the three NACs, PA is the most efficient quencher. KSV values of TPTs for various NACs are comparable with those of previously reported polymers.

Preparation and characterization of two new triptycene based polytopic Pt(II) organometallic complexes are being reported. These complexes have three trans-bromobis(trialkylphosphine)platinum(II) units directly attached to the central triptycene unit. These organoplatinum complexes were converted to the corresponding nitrate salts for subsequent use in self-assembly reactions. Characterization of these organometallic triptycene complexes by multinuclear NMR, FTIR, mass spectrometry and elemental analyses is described. The molecular structure of one of the organoplatinum triptycene tripods was determined by single-crystal X-ray crystallography. The potential utility of these organometallic tritopic acceptors as building blocks in the construction of metallasupramolecular cages containing the triptycene motif is explored. Additionally, for the first time, 3,3′-bipyridine has been used as a flexible donor tecton for self-assembly of discrete and finite metallacages using triptycene based tritopic organometallic acceptor units. Triptycene motif containing supramolecules were characterized by multinuclear NMR (including 1H DOSY), mass spectrometry and elemental analyses. Geometry of each supramolecular framework was optimized by employing the PM6 semiempirical molecular orbital method to predict its shape and size.

Synthesis of new triptycene-containing polyamides (TPAs) using 2,6-diaminotriptycene and various aromatic and aliphatic dicarboxylates (Yamazaki–Higashi phosphorylation polyamidation) is described. The effect of the polymer backbone flexibility on the surface morphology of the respective polymer is studied. Polyamides thus prepared are organosoluble and have relatively low solution viscosities (0.18–0.5 dL g−1). TGA indicated that triptycene polyamides containing aliphatic chains are thermally less stable than the wholly aromatic triptycene polyamides. These polyamides may be categorized as self-extinguishing materials. FTIR spectroscopy studies show that hydrogen bonding interactions are weaker in wholly aromatic polyamides (TPA1–TPA3) relative to those in semi-aromatic polyamides (TPA4–TPA6). FE-SEM images of TPAs show that replacement of aromatic dicarboxylates with aliphatic dicarboxylates results in a drastic change in the morphology of the polyamides.

•Facile synthesis of 2,6,14- and 2,7,14-triptycenetripropiolic acids in high yields.•Unique examples of triptycene based tripodal chemosensors.•Selective and specific detection of Hg2+/Fe3+ in pure aqueous media.•Low detection limits for Hg2+/Fe3+ using fluorescence (turn off) spectroscopy.•pH dependence of fluorescence quenching of receptors has been investigated.Synthesis and characterization of two trisubstituted triptycene derivatives in high yields are being reported. Aqueous solutions of sodium salt of 2,6,14- and 2,7,14-triptycenetripropiolic acids (1c and 2c) have shown high selectivity for Hg2+ and Fe3+ ions, through quenching of fluorescence intensity, when tested in presence of other metal ions in pure aqueous medium. In addition, pH dependence of fluorescence quenching has been studied. Binding stoichiometry between probes and metal ions (Hg2+ and Fe3+) has been studied using Job’s plot, and corresponding association constant has been evaluated. 1c and 2c are the unique examples of triptycene based tripods that act as chemosensors for selective detection of metal ions.Two new trisubstituted triptycene derivatives (2,6,14- and 2,7,14-triptycenetripropiolic acids) were synthesized and characterized. Sodium salt of these tricarboxylic acids have shown high selectivity for mercury(II) and iron(III) ions, through quenching of fluorescence intensity, in pure aqueous medium. In addition, pH dependence of fluorescence quenching has been studied.

Two triptycene-based ligands with pendant bromophenyl units have been prepared. These triptycene derivatives have been used as synthons for the synthesis of di and tri nuclear palladium complexes. The organic molecules and their corresponding organometallic complexes have been fully characterized using nuclear magnetic resonance (NMR), infrared (IR) spectroscopy and mass spectrometry. The mode of binding and effect of the complexes on pUC19 plasmid, calf thymus DNA and oligomer duplex DNA have been investigated by a host of analytical methods. The complexes brought about unwinding of supercoiled plasmid and the unwinding angle was found to be related to the binding affinity of the complexes with DNA, where both these parameters were guided by the structure of the complexes. Concentration-dependent inhibition of endonuclease activity of SspI and BamHI by the complexes indicates preference for G/C sequence for binding to DNA. However, neither the complexes did not introduce any cleavage at abasic site in oligomer duplex DNA, nor they created linear form of the plasmid upon co-incubation with the DNA samples. The interactions of the complexes with DNA were found to be strongly guided by the structure of the complexes, where intercalation as well as groove binding was observed, without inflicting any damage to the DNA. The mode of interaction of the complexes with DNA was further confirmed by isothermal calorimetry.

Synthesis and characterization of four new tripodal linkers each with a central triptycene unit and pendant pyridine unit have been reported. These tripods have flexible arms due to the presence of amide linkages that bridge the peripheral pyridine units and central triptycene core. Self-assembly of one of the tripods with Pt(II) based ditopic acceptor unit is the first example of a truly supramolecular cage based on a triptycene tecton. Additionally, this metallacage also represents the unique example of a Pt(II) based trigonal bipyramidal (TBP) cage containing amide functionality.

The synthesis and characterization of a new pyrazine-based “flexible” and ditopic platinum(II) organometallic molecule (3) is being reported. Flexibility in this molecule is due to the presence of ether functional groups that bridge the rigid core and periphery. Due to the presence of square planar Pt(II) centers at the two ends, the molecule's potential to act as an acceptor building block in the construction of metallamacrocycles was tested. Upon reaction of 3 with various dicarboxylates in a 1:1 stoichiometric ratio, [2 + 2] self-assembled neutral metallacycles (M1–M3) were obtained in high yields. M1–M3 were characterized using multinuclear NMR, high resolution mass spectrometry and elemental analyses. The shape and dimensions of these supramolecular structures were also confirmed by optimizing the geometry using the density functional theory (DFT) approach. Computational studies suggest that M1–M3 are nanoscalar macrocyles. Furthermore, using isothermal titration calorimetry (ITC), it was shown that 3 can bind with picric acid (PA) to yield a 3·(PA)2 host–guest complex. The magnitude of the binding constant indicates that 3 has significant affinity for PA.

We report a facile synthesis of 2,6-diethynyltriptycene (DET) in high yield. Application of DET as monomer in polymer chemistry has been shown (for the first time) in syntheses of two novel polymers via Sonogashira cross-coupling reaction in high yield. The newly synthesized polymers were characterized by FT-IR, UV–vis absorption, and NMR spectroscopic techniques. The polymers prepared using DET have interesting properties such as high solubility in common organic solvents, high thermal stability [decomposition temperatures (Td) > 495 °C], and high char yield (greater than 81% at 900 °C). Additionally, polymers are fluorescent. Host–guest interaction between triptycene-based polymers and fullerene (C60) has been studied for the first time. Fluorescence quenching of our polymers by C60 has been used to study the extent of (polymer·C60) host–guest complex formation. Fluorescence quenching studies indicate binding constant for polymer·C60 complexation on the order of 105 M–1.

Preparation and characterization of two new triptycene based polytopic Pt(II) organometallic complexes are being reported. These complexes have three trans-bromobis(trialkylphosphine)platinum(II) units directly attached to the central triptycene unit. These organoplatinum complexes were converted to the corresponding nitrate salts for subsequent use in self-assembly reactions. Characterization of these organometallic triptycene complexes by multinuclear NMR, FTIR, mass spectrometry and elemental analyses is described. The molecular structure of one of the organoplatinum triptycene tripods was determined by single-crystal X-ray crystallography. The potential utility of these organometallic tritopic acceptors as building blocks in the construction of metallasupramolecular cages containing the triptycene motif is explored. Additionally, for the first time, 3,3′-bipyridine has been used as a flexible donor tecton for self-assembly of discrete and finite metallacages using triptycene based tritopic organometallic acceptor units. Triptycene motif containing supramolecules were characterized by multinuclear NMR (including 1H DOSY), mass spectrometry and elemental analyses. Geometry of each supramolecular framework was optimized by employing the PM6 semiempirical molecular orbital method to predict its shape and size.

Herein, facile synthesis and characterization of four triazole linked network polymers (TNPs) in high yields is described. These nitrogen rich polymers are derived using a “click” reaction between 2,6,14-triazido triptycene and various di- or triethynyl comonomers. The TNPs are microporous and exhibit high surface area (SABET up to 1348 m2 g−1). Due to the incorporation of the 1,2,3-triazole motif (a CO2-philic moiety), the TNPs record moderate to high CO2 uptake (up to 4.45 mmol g−1 at 273 K and 1 bar). The TNPs also show very good CO2/N2 (up to 48) and CO2/CH4 (8–9) selectivity. While the highest storage capacity has been registered by TNP4 (CO2 4.45 mmol g−1 at 273 K and 1 bar, CH4 23.8 mg g−1, H2 1.8 wt%), the highest CO2/N2 and CO2/CH4 selectivity is shown by TNP3 which contains additional nitrogen rich building blocks in the form of heteroaromatic pyrazine rings. These results suggest that TNPs are porous materials with potential practical application in gas storage and separation.