The structures and properties of two mononuclear Dy(III) enantiomeric pairs were dramatically controlled by crystallization temperature; the enantiomeric pair with coordinated chiral N,N′-donor ligands exhibits enhanced single-ion magnetic, ferroelectric and chiroptical properties with respect to the other one with protonated chiral N,N′-donor ligands.

The hydrothermal reaction of Mn(II) or Co(II) ions with 2-carboxyethyl(phenyl)phosphinic acid (H2L) afforded Mn(II) and Co(II) carboxylate–phosphinates containing μ3-OH− as a co-ligand, namely [M3(L)2(OH)2] (M = Mn (1) or Co (2)). Such two compounds feature a new layered structure in which Δ-type chains built from alternating corner- and edge-sharing M3(μ3-OH) triangles are further connected via the Y-shaped “–(CH2)2–C(–O–)–” spacers. Magnetic studies reveal that there are dominant antiferromagnetic interactions between the metal ions. In 1, the complicated magnetic couplings in the Δ-type chains result in spin competition, displaying spin-glass behaviors. In 2, spin fluctuation behavior was observed and the critical field at 2 K is 25 kOe.

A new family of 3d–4f heterometallic trinuclear complexes, namely [M2LnL2]·2ClO4·H2O (H3L = tris(((2-hydroxy-3-methoxybenzy1)amino)ethyl)amine, where M = Ni, Ln = Gd (1), Dy (2), and M = Zn, Ln = Gd (3), Dy (4)) were synthesized via the reaction of H3L and Ln(NO3)3·6H2O and Ni(ClO4)2·6H2O or Zn(ClO4)2·6H2O in a 2 : 1 : 2 ratio in the solution. Complexes 1–4 consisted of three metal ions arranged in an isosceles triangle manner. Magnetic properties investigations showed that complexes 1 and 2 exhibited weak ferromagnetic coupling between the Ni(II) and Ln(III) ions, whereas complex 4 displayed lanthanide single-ion magnetic properties. The alternating current (ac) magnetic susceptibilities of 4 revealed that both the in-phase (χ′) and out-of-phase (χ′′) signals are frequency- and temperature-dependent, which are typical features of the field-induced slow relaxation of the magnetization with Ueff = 124.5 K. Complex 4 also exhibited an obvious butterfly-shaped hysteresis loop at 2 K, indicating that it is a single-ion magnet. Moreover, complex 4 showed stronger fluorescent emissions, which were typical narrow emission bands of lanthanide ions. Therefore, complex 4 can be considered as a molecular magnetic and luminescent material. Comparably, complex 2 showed very weak DyIII-based emissions because the paramagnetic NiII ions quench the fluorescence and thereby lower the population of the triplet state.

Reactions of DyCl3·6H2O or Dy2O3 with 2-quinolinecarboxylic acid (H-QLC) yielded two compounds, namely, [Dy4(QLC)12(H2O)6]·4H2O (1) and [Dy(QLC)3(H2O)2]n (2). Compound 1 is a linear tetranuclear structure with one central [Dy2(QLC)4(H2O)4] subunit and two terminal [Dy(QLC)3(H2O)] subunits linked by bridging QLC− ligands. Compound 2 has a one-dimensional (1D) chain wherein the [Dy(QLC)2] unit formed by two QLC− ligands chelating a Dy(III) ion is connected by the bridging QLC− ligands. Compounds 1 and 2 exhibit slow magnetic relaxation behaviour in the absence of a static magnetic field, which is rarely observed in lanthanide-carboxylate compounds. During the structural evolution from a linear Dy4 cluster of 1 into a 1D chain of 2, the anisotropy energy barrier (Ueff) is enhanced from 45.4(2) to 144.2(1) K. Though the Dy(III) centers in 1 and 2 all are eight-coordinated with square antiprismatic coordination environments, the higher energy barrier observed for 2 could be the result of a more favorable crystal field for the Dy(III) ions in 2.

Two dysprosium(III) complexes derived from 2,2′-bipyridine-6,6′-dicarboxylic acid (H2bpdc), [Dy(bpdc)(Hbpdc)]·3H2O (1) and [Dy2(bpdc)3(H2O)3]·2.125H2O (2), were isolated from the same hydrothermal reaction container as different phases. Compound 1 is a mononuclear complex with a DyN4O4 coordination polyhedron; whereas compound 2 is a dinuclear complex with two types of eight coordinated dysprosium(III) ions, showing DyN4O4 and DyN2O6 coordination polyhedra, respectively. Remarkably, a new type of (H2O)6 supramolecular aggregate exists in the crystal structure of 2. Magnetic investigations revealed that 1 is a field-induced single-ion magnet with an effective energy barrier of 45.6 K, exhibiting two-step magnetic relaxation; while an intramolecular ferromagnetic interaction exists in 2, which is a field-induced single-molecule magnet, displaying two-step magnetic relaxation too, with effective energy barriers of 53.4 and 92.1 K, respectively.

The reactions of NiII or CuII ions with N3− anions in the presence of templated diethyl or triethyl amines afford three new azido-bridged coordination polymers, namely, [Ni(N3)2(Deeda)] (1), (DeaH)[Cu3(N3)7] (2), and (TeaH)[Cu4(N3)9] (3), where Deeda, (DeaH)+ and (TeaH)+ represent N,N-diethylethane-1,2-diamine, diethylammonium and triethylammonium, respectively. Magnetic studies revealed that they exhibit metamagnetism, spin glass and canted ferromagnetism, respectively, induced by different coordination modes of the azide ligands.

A novel 3D MOF based on dysprosium(III) oxalate and 1,10-phenanthroline (phen), {[Dy(C2O4)1.5phen]·0.5H2O}n (1), has been hydrothermally synthesized. The Dy3+ ion acts as a typical Y-shaped node, linking to each other to generate an interesting 3D topology structure. Complex 1 is the first 3D DyMOF displaying both ferromagnetic coupling and field-induced two-step magnetic relaxation.

Three types of lanthanide complexes based on the tetrazole-1-acetic acid ligand and the 2,2′-bipyridine coligand were prepared and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analyses; the formulas of these complexes are [Ln2(1-tza)4(NO3)2(2,2′-bipy)2] (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5)), [Dy2(1-tza)4Cl2(2,2′-bipy)2] (6), and [Yb2(1-tza)4(NO3)2(2,2′-bipy)2] (7) (1-tza = tetrazole-1-acetate and 2,2′-bipy = 2,2′-bipyridine). They are dinuclear complexes possessing similar structures but different lanthanide(III) ion coordination geometries because of the distinction of peripheral anions (such as NO3– and Cl–) and the effect of lanthanide contraction. The variable-temperature magnetic susceptibilities of 1–6 were measured. Both DyIII complexes (5 and 6) display field-induced single-molecule magnet behaviors. Ab initio calculations revealed that the DyIII complex 6 possesses a more anisotropic DyIII ion in comparison to that in 5. The room-temperature photoluminescence spectra of SmIII (1), EuIII (2), TbIII (4), and DyIII (5 and 6) complexes exhibit strong characteristic emissions in the visible region, whereas the YbIII (7) complex shows near-infrared (NIR) luminescence.

A new family of 3d–4f dinuclear complexes derived from a chiral Schiff-base ligand, (R,R)-N,N′-bis(3-methoxysalicylidene)cyclohexane-1,2-diamine (H2L), has been synthesized and structurally characterized, namely, [Cu(L)Ln(NO3)3(H2O)] (Ln = Ce (1) and Nd (2)), [Cu(L)Sm(NO3)3]·2CH3CN (3) and [Cu(L)Ln(NO3)3] (Ln = Eu (4), Gd (5 and 5′), Tb (6 and 6′), Dy (7 and 7′), Ho (8), Er (9) and Yb (10)). Structural determination revealed that these complexes are composed of two diphenoxo-bridged CuII–LnIII dinuclear clusters with slight structural differences. Complexes 1, 2 and 4–7 crystallize in the chiral space group P1, and the space group of 3 is P21, while the other six complexes (5′–7′ and 8–10) are isomorphous and each of them contains two slightly different CuII–LnIII dinuclear clusters in the asymmetric unit with the chiral space group P21. Magnetic investigations showed that ferromagnetic couplings between the CuII and LnIII ions exist in 5–7 and 5′–7′. Moreover, the alternating current (ac) magnetic susceptibilities of 6, 6′, 7 and 7′ showed that both the in-phase (χ′) and out-of-phase (χ′′) are frequency- and temperature-dependent with a series of frequency-dependent peaks for the χ′′, which being typical features of field-induced slow magnetic relaxation phenomena. For 8, a frequency dependent χ′ with peaks but χ′′ without peaks appeared; however, the compound displays field-induced slow magnetic relaxation behavior. Furthermore, no obvious frequency-dependent ac signal was observed in 9 owing to the absence of the easy-axis anisotropy. More significantly, we observed the temperature-controlled reversible conversion from one chiral single-crystal (5–7) to another chiral single-crystal (5′–7′) exhibiting slow magnetic relaxation.

A novel lanthanide metal–organic framework was yielded by a hydrothermal reaction of 5-chloro-6-hydroxypyridine-3-carboxylic acid (5-Cl-6-HOPy-3-CO2H) and Dy2O3 in the presence of oxalic acid [H2(OX)], namely, {[Dy2(1H-5-Cl-6-Opy-3-CO2)2(OX)2(H2O)]·2H2O}∞ (1, 1H-5-Cl-6-Opy-3-CO2− = 1-hydro-5-chloro-6-oxopyridine-3-carboxylate, which was formed by the autoisomerization of single deprotonated 1H-5-Cl-6-HOpy-3-CO2− anion). The dysprosium(III) ions are bridged by oxalate anions to construct an interesting 4-connected layer network with a Schälfli topology symbol of (32·52) (3·53), such layers are connected with each other by the 1H-5-Cl-6-HOpy-3-CO2− anions to form a three-dimensional framework. Magnetic investigations indicated that 1 is a field-induced single-molecule magnet, displaying two-step thermal magnetic relaxation, with an effective thermal barrier of 37.6 K. Surprisingly, a zigzag chain-like gadolinium(III) complex, {[Gd(1H-5-Cl-6-Opy-3-CO2)2(OX)0.5(H2O)3]·6H2O}∞ (2), was isolated using Gd2O3 instead of Dy2O3 owing to the lanthanide contraction effect. Notebaly, a unique F-shaped (H2O)6 supramolecular aggregate exists in the crystal structure of 2.

Three lanthanide coordination polymers containing both nicotinate N-oxide and glutarate, {[Ln(NNO)(glu)]·0.25H2O}∞ (Ln = Eu, 1; Ln = Gd, 2; Ln = Dy, 3; HNNO = nicotinic acid N-oxide, H2glu = glutaric acid), have been hydrothermally synthesized, which are isostructural, showing 2D layer network structures. The europium(III) species displays typical narrow fluorescent emission bands of the lanthanide ion, with the absolute emission quantum yield of 0.055 and the fluorescence lifetime of 4.2 ns. Magnetic determinations revealed that a weak antiferromagnetic interaction exists in the gadolinium(III) complex, while the dysprosium(III) analogue exhibits field-induced two-step magnetic relaxation, with an effective thermal barrier of 44.2 K.

A new two-dimensional (2D) lanthanide metal–organic framework, {[Dy2(HCAM)3(H2O)4]·2H2O}n (1, H3CAM = 4-hydroxypyridine-2,6-dicarboxylic acid) has been hydrothermally synthesized and structurally characterized using single-crystal X-ray diffraction. There are two crystallographically independent dysprosium atoms in 1, displaying spherical tricapped trigonal prism geometry and square antiprism geometry, respectively. The dysprosium(III) ions are connected with each other through the bridging HCAM2− anions, generating a classical 2D (4, 4) grid structure. Magnetic investigations revealed that intramolecular ferromagnetic interactions exist among the dysprosium(III) ions in 1, which shows field-induced two-step thermal magnetic relaxation, with the effective thermal barriers of 63.5 K and 57.1 K, respectively.

A new family of homochiral lanthanide dinuclear complexes based on a chiral carboxylate, namely [Ln(R-pba)3(phen)]2 (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9) and Ho (10), R-pba = (R)-2-phenylbutyric acid, phen = 1,10-phenanthroline), have been synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analyses and IR spectra. Complexes 1–10 are isostructural and crystallize in the chiral space group P21. Their optical activity and enantiomeric nature were confirmed by the circular dichroism spectra. Complexes 6, 8 and 9 exhibit strong fluorescent emissions with typical narrow emission bands of lanthanide ions and 6 and 8 display relatively high quantum yields. Magnetic investigations revealed that the weak antiferromagnetic exchange and/or the depopulation of the Ln(III) excited Stark sub-levels which exist in 7–10.

•Chiral nickel–lanthanide complexes derived from Schiff-base were synthesized.•The circular dichroism spectra and magnetic properties were investigated.•Complexes Ni–Tb and Ni–Dy exhibit field-induced single-molecule magnet behaviors.A new family of nickel–lanthanide heterometallic dinuclear complexes derived from a chiral Schiff-base ligand, (R,R)-N,N′-bis(3-methoxysalicylidene)cyclohexane-1,2-diamine (H2L), namely [Ni(L)Ln(NO3)3(H2O)] (Ln = Ce (1), Nd (2)) and [Ni(L)Ln(NO3)3] (Ln = Sm (3), Eu (4), Gd (5), Tb (6), Dy (7) and Yb (8)) have been synthesized and structurally characterized. X-ray single-crystal structure determination revealed that these complexes are diphenoxo-bridged NiII–LnIII dinuclear clusters, which crystallize in the chiral space group P1. The solid circular dichroism (CD) spectra confirmed the optical activity and enantiomorphous properties of all these complexes. Magnetic investigations suggested that crystal-field effects and/or the possible antiferromagnetic dipole–dipole interaction between the molecules exist in the complexes and single-ion properties of LnIII ions lead to their magnetic behaviors. The alternating current (ac) magnetic susceptibilities showed that complexes 6 and 7 exhibit field-induced single-molecule magnet behaviors due to the strong anisotropy and important crystal-field effect of the TbIII or DyIII ions. It is noteworthy that the quantum tunneling effect at low temperatures can be effectively suppressed by employing a 2 kOe direct current field.A new family of nickel–lanthanide heterometallic dinuclear complexes is constructed from a chiral Schiff-base ligand. They show single-ion magnetic properties duo to the diamagnetic nickel ion with square coordination geometry, both the Ni–Dy complex and the Ni–Tb complex of them are chiral field-induced SMMs.

Two hexanuclear 3d–4f cluster complexes containing the pyridine-2-aldoximate ligand (pao−), [Ni2Ln4 (hfac)8(pao)6(CH3COO)2(MeOH)]·H2O·MeOH (Ln = Gd, 1; Ln = Dy, 2; hfac− = hexafluoroacetylacetonate), have been synthesized, which show similar structures with an interesting ‘trigonal bipyramid’ metal topology. Magnetic determinations revealed that the Ni–Gd species has a spin ground state of 16 due to the dominant ferromagnetic exchange, exhibiting an enhanced magnetocaloric effect, which can be used as a cryogenic magnetic cooler; while the Ni–Dy analogue displays slow magnetic relaxation, a typical characteristic of a single-molecule magnet.

The hydrothermal reaction of 4,4′-dicarboxybiphenyl sulfone and dysprosium(III) nitrate in the presence of L-histidine yielded the first 2D → 2D polyrotaxane lanthanide–organic framework, which possesses both polyrotaxane and polycatenane topology features. Magnetic investigations indicated that it is a field-induced single-molecule magnet with two-step magnetic relaxation processes.

•A novel chiral dinuclear Cu(II) cluster has been synthesized and characterized.•The two Cu ions in complex 1 are sitting in a distorted octahedral arrangement.•Inversion crystallographic symmetry gives dimers as either Λ or Δ isomers.•Magnetic susceptibility measurements indicate the presence of ferromagnetic Cu⋯Cu exchange.A novel chiral dinuclear Cu(II) cluster [Cu2(bpca)(bpy)(H2O)(NO3)3] (1) (bpca− is the anion of bis(2-pyridylcarbonyl)amine and bpy is 2,2′-bipyridine), was synthesized and characterized. Single crystal X-ray diffraction analysis showed that the two Cu(II) ions in complex 1 are sitting in a distorted octahedral arrangement and bridged by the organic spacer bpca−. Hydrogen bonding links neighboring dinuclear units into a three-dimensional framework. Inversion crystallographic symmetry gives dimers as either Λ or Δ isomers. Racemization of complex 1 was confirmed by circular dichroism (CD) spectroscopy. The temperature dependence of the magnetic susceptibility for complex 1 in the range 2–300 K indicates the presence of ferromagnetic Cu⋯Cu exchange. The data fitting gave the magnetic coupling constant J = 8.08 cm−1.A novel chiral dinuclear Cu(II) cluster [Cu2(bpca)(bpy)(H2O)(NO3)3] (1) was synthesized and characterized. Single crystal X-ray diffraction analysis showed that the two Cu(II) ions in complex 1 are sitting in a distorted octahedral arrangement and bridged by the organic spacer bpca. Inversion crystallographic symmetry gives dimers as either Λ or Δ isomers. The magnetic studies indicate that Cu(II) ions in complex 1 are ferromagnetically coupled with the magnetic coupling constant J = 8.08 cm−1.

A pair of homochiral β-diketonate ligands (+)-3-trifluoroacetyl)camphor (d-Htfc) and (−)-3-trifluoroacetyl)camphor (l-Htfc) were used to construct two enantiomeric pairs of Dy(III) single-ion magnets [Dy(d-tfc)3(bpy)]2 (d-1)/[Dy(l-tfc)3(bpy)]2 (l-1) (bpy = 2,2′-bipyridine) and [Dy(d-tfc)3(phen)]·2H2O (d-2)/[Dy(l-tfc)3(phen)] (l-2) (phen = 1,10-phenanthroline). The capping aromatic N,N′-donors have a dramatic influence on the structural and magnetic characteristics of the Dy(III) β-diketonate enantiomeric pairs: the cocrystal of two homochiral Dy(III) β-diketonate stereoisomers with the 2,2′-bipyridine ligand was formed, showing field-induced single-ion magnet behaviors with a two-step relaxation process, while no stereoisomerization happened for the homochiral Dy(III) β-diketonate with the 1,10-phenanthroline coligand, exhibiting a single relaxation process of the magnetization only. The anisotropy barriers of d-1 (36.5 and 46.1 K) are slightly smaller than those of l-1 (37.0 and 49.3 K), while d-2 has a larger energy barrier (30.5 K) with respect to l-2 (25.1 K).

An alkoxido-bridged tetranuclear Dy(III) complex, [Dy4(H3L)2(OAc)6]·2EtOH {1, H6L = 1,3-bis[tris(hydroxymethyl)methylamino]propane}, has been solvothermally synthesized and characterized. An X-ray crystallographic study revealed that complex 1 possesses a novel “parallelogram” [Dy4(OCH2–)4] core, and a new binding mode η3:η3:η1:η1:η1:η2:μ4 of the Bis-tris propane ligand was observed. Magnetic investigations indicated that it is a single-molecule magnet (SMM), showing two distinct magnetic relaxation processes with the energy barriers of 44 K and 107 K, respectively. Such a two-step magnetic relaxation process could be well described by the sum of two modified Debye functions.

Reaction of the chiral ligand (−)-4,5-pinenepyridyl-2-pyrazine (L) with Ln(hfac)3·2H2O precursors [hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonate, Ln = Sm3+ (1), Eu3+ (2), Tb3+ (3) and Dy3+ (4)] in methanol solution led to the formation of four noncentrosymmetric lanthanide complexes with the general formula [Ln(hfac)3L]n·H2O. The single-crystal X-ray diffraction analyses revealed that they are isostructural and take a one-dimensional (1D) chain structure based on the Ln(hfac)3L repeating units, in which the nine-coordinate Ln3+ ions reside in a tricapped trigonal prism (TTP) environment never reported in previous 1D chain lanthanide complexes. The investigations of their photophysical properties showed that complexes 1, 2 and 3 exhibit characteristic emissions of Sm3+, Eu3+ and Tb3+ ions with respective luminescent lifetime values of 0.065, 1.066 and 0.129 ms, while complex 4 does not display any emission. The different luminescent intensities and lifetimes among them were further discussed in detail. Moreover, the magnetic properties of complexes 1–4 were assessed with a special emphasis on the Dy3+ complex 4. Alternating-current (ac) magnetic susceptibility measurements indicated that field-induced two-step slow magnetic relaxation processes were observed in 4, indicating the single-molecule magnet (SMM) behavior of 4. In addition, the noncentrosymmetric complexes 1–4 crystallizing in the same polar point group (Cs) exhibit both ferroelectric and nonlinear optical properties at room temperature. All these features make them multifunctional crystalline molecule materials.

Two new sandwich calix[4]arene-supported cluster complexes, [Ln4(OH)4(TBSOC)2(H2O)4(CH3OH)4]·4H2O (H4TBSOC = p-tert-butylsulfonylcalix[4]arene; Ln = Dy, 1; Ln = Ho, 2), have been prepared and characterized. An X-ray crystallographic study reveals that both complexes contain a holistically disordered [Ln4(OH)4]8+ cubane cluster core, which is sandwiched between two antiparallel calixarene macrocycles. Magnetic investigations indicate that complex 1 displays slow magnetization relaxation typical for single-molecule magnets in the absence of a static applied dc field, with the ΔE/kB parameter of 22.9 K, the largest value for the calixarene-supported pure 4f single-molecule magnets so far, whereas complex 2 does not show any relaxation of the magnetization above 2 K.

Three new manganese(III) compounds have been synthesized via in situ ligand transformation and oxidation of Mn(II) ions. In the presence/absence of N3− anion in the reaction solutions, the dinuclear/mononuclear Mn(III) coordination compounds were formed, respectively. A structural analysis of the dinuclear compounds (1, 2) shows that the six coordination Mn(III) atoms are linked by two methanolato oxygen atoms from two ligands to form a rectangular arrangement of the metal ions and oxygen atoms. In complex 3, two facially coordinating tridentate ligands are bound to the Mn(III) ion, resulting in a MnN4O2 chromophore with an axially-compressed octahedral geometry. In addition, variable-temperature magnetic analysis of 1 shows that a weak antiferromagnetic coupling interaction was mediated through the methanolato oxygen bridge between two Mn(III) ions and the exchange parameter is given as J = − 3.6 cm− 1.Graphical abstractThree new manganese(III) compounds have been synthesized via in situ ligand transformation and oxidation of Mn(II) ions. The crystal structure and magnetic properties of these complexes have been studied.Highlights► Three Mn(III) compounds have been synthesized via in situ ligands transformation. ► In the presence/absence of N3–, the di-/mononuclear Mn(III) compounds were formed. ► The crystal structure and magnetic properties of these complexes have been studied.

Both ferromagnetic and ferroelectric properties were observed in two enantiomerically pure nanoscale manganese cluster complexes supported by chiral Schiff base ligands, each of which comprises a 22-nucleus mixed-valence manganese(II/III) supratetrahedral cluster cation and an equilateral-triangle trinuclear manganese(III) cluster anion with C3 symmetry.

Hydrothermal reactions of FeIII or CoII ion with dimethyl methylsulfonomethanephosphonate afforded two novel layered transition metal phosphonates containing oxo-bridging hydroxides (H2O or OH−) as coligands, namely, [Fe(L)(OH)(H2O)] (1) and [Co4(L)4(H2O)4]·2H2O (2) (H2L = CH3SO2CH2PO3H2). Magnetic property studies reveal that spin-canting and metamagnetic behaviors coexist in complex 2 with a Tc of 7.0 K.

The screw propeller-like cluster complex [Mn3(OMe)(LSchiff)3(H2O)Cl2]·2H2O {H2LSchiff = 2-[(E)-(R)-1-hydroxypropan-2-ylimino]methyl-6-methoxyphenol} is the first chiral triangle manganese cluster compound. It is also a rare nonsymmetrical triangle compound with an unequilateral arrangement of three manganese(III) atoms. Both ferromagnetic and antiferromagnetic interactions exist between the Mn3+ ions, exhibiting a magnetic anisotropy.

Two novel coaxial double-screw-propeller heptanuclear 3d–4f cluster complexes are ferromagnetic: one exhibits a large magnetocaloric effect while the other a magnetic relaxation behavior, depending on the lanthanoid ions used.

The new azido-bridged cobalt cluster complex, [Co2IICo2IIIμ1,1-N3)4(N3)2(HDMSP)2(MeOH)2]·2H2O (H3DMSP = 1,3-dihydroxy-2-methyl-2-(salicylideneamino)propane), is the first azido-bridged mixed-valent cobalt complex showing a defective double cubane structure. Magnetic study indicated that there is an antiferromagnetic interaction between two Co2+ ions.The first azido-bridged mixed-valent cobalt defective double cubane cluster complex was synthesized and characterized structurally and magnetically.

The wheel-shaped heptanuclear cluster complex {[Mn4Na3(thmp)2(acac)6(H2O)6]CH3COO}·4H2O is the first heterometallic mixed-valent disklike compound with apical alkali-metal ions. The weak ferromagnetic interaction between the central Mn4+ ion and the peripheral Mn2+ ones leads to a high-spin ground state (S = 9).

The coordination of methanol and ethanol molecules was observed in the construction of three 1D coordination polymers composed of anti−anti carboxylato-bridged MnIII3O(Brppz)3 units [Brppz = 3-(5-bromine-2-phenolate)pyrazolate]. The difference in these 1D complexes’ structures induced by methanol and ethanol solvents leads to the variation of the magnetic properties. The methanol solvent product 1 [MnIII3O(Brppz)3(MeOH)3(AcO)]·0.5MeOH has a MnIII3O repeating unit with two octahedral configuration manganese(III) ions and one square-pyrimid configuration manganese(III) ion, showing a long-range magnetic ordering with a Tc of 8.2 K, whereas the ethanol solvent products 2 [MnIII3O(Brppz)3(C2H5OH)4(AcO)] (α-phase) and 3 [MnIII3O(Brppz)3(C2H5OH)4(AcO)] (β-phase) are polymorphs, both having a MnIII3O repeating unit with three octahedral configuration manganese(III) ions, displaying single-chain magnet behaviors. Products 2 and 3 represent the first examples of polymorphs of single-chain magnets. Furthermore, the bridging carboxylate ligand in these 1D complexes was generated by the decomposition of β-diketones via the retro-Claisen condensation reactions in the presence of strong bases.

Two couples of enantiomerically pure chiral cyano-bridged heterobimetallic chain coordination polymers, [Mn((R,R)-Salcy)Fe(Tp)(CN)3·H2O·1/2CH3CN]n (1), [Mn((S,S)-Salcy)Fe(Tp)(CN)3·H2O·1/2CH3CN]n (2), [Mn((R,R)-Salcy)Fe(bpca)(CN)3·H2O]n (3), and [Mn((S,S)-Salcy)Fe(bpca)(CN)3·H2O]n (4) [(R,R)-Salcy or (S,S)-Salcy = (R,R)- or (S,S)-N,N′-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion, Tp = tris(pyrazolyl)hydroborate, bpca = bis(2-pyridylcarbonyl)amidate anion], were synthesized using the modified cyanometalate building blocks [Fe(L)(CN)3]− (L = Tp, bpca) and the chiral polydentate Schiff base manganese(III) complex fragments. The circular dichroism measurements showed Cotton effects of the opposite sign at the same wavelength for each pair of enantiomers. Magnetic property studies indicated that complexes 1 and 2 show not only intrachain but also interchain field-induced metamagnetic transitions from an antiferromagnetic to a ferromagnetic state and exhibit an antiferromagnetic long-range ordering with a TN of 3.2 K, while enantiomers 3 and 4 are typical antiferromagnetic coupling compounds. Furthermore, complex 3 exhibits a ferroelectric behavior that relates to the polar point group C2, in which it crystallizes.

6-Hydroxypyridine-3-carboxylic acid (6-HOPy-3-CO2H) reacts with Ln2O3 (Ln = Nd, Sm, Eu, Gd) and oxalic acid (H2OX) under hydrothermal conditions to generate four novel lanthanide–organic coordination polymeric networks [Ln2(1H-6-Opy-3-CO2)2(OX)2(H2O)3]·2.5H2O (Ln = Nd, 1; Sm, 2; 1H-6-Opy-3-CO2− = 1-hydro-6-oxopyridine-3-carboxylate) and [Ln(1H-6-Opy-3-CO2)(OX)(H2O)2]·H2O (Ln = Eu, 3; Gd, 4). The new co-ligand 1H-6-Opy-3-CO2− anion was generated by the autoisomerization of the single deprotonated 6-HOPy-3-CO2− anion (from the enol form into the ketone one). 1 and 2 are isomorphous, they possess a three-dimensional architecture constructed from Ln3+ ions bridged by oxalate anions and two types of 1H-6-Opy-3-CO2− bridges, showing a three-nodal (4,5)-connected topology (3.42.52.63.7.8)2(3.53.62)2(32.6.72.8) or a simplified uninodal 6-connected topology (33.46.55.6), both topologies are completely new; while only one type of 1H-6-Opy-3-CO2− bridge is used to construct the two-dimensional layer networks of 3 and 4 besides oxalate bridges, both complexes 3 and 4 are isostructural, exhibiting the honeycomb topology 63. The lanthanide contraction effect is believed to play a key role in directing the formation of a particular structure. A magnetic study of 1–3 indicated that the coupling interaction between Ln3+ ions is weak.

A new one-dimensional (1D) copper(II) complex, [Cu2(dpk · CH2O)(N3)3]n (dpk · CH2OH = unimethylated diol of di-2-pyridyl ketone) (1), has been synthesized and characterized. X-ray crystal structure study reveals that 1 is composed of 1D copper(II) chain with alternating double EO-azido bridges and mixed EO-azido/alkoxo double bridges. The magnetic determination indicates that ferromagnetic interaction dominates in this new 1D S = 1/2 system.A novel one-dimensional (1D) copper(II) coordination polymer with alternating double EO-azido bridges and mixed EO-azido/O double bridges, [Cu2(dpk · CH2O)(N3)3]n (dpk · CH2OH = unimethylated diol of di-2-pyridyl ketone) (1), was synthesized and characterized, which represents a new type of 1D CuII magnetic system.

The non-uniform chain manganese(III) complex constructed from EE-azido bridged MnIII3O units, [MnIII3O(Brppz)3(MeOH)3(N3)]·2MeOH [1, Brppz = 3-(5-bromo-2-phenolate)pyrazolate], is the first example of 1D azido-bridged coordination polymer showing both solvatomagnetic effect and spin-glass behavior.

In situ hydrothermal decarboxylation was observed during preparing two novel three-dimensional (3D) lanthanide–organic frameworks Ln(2,5-PyDC)(3-PyC)(H2O) (Ln = Nd, Sm; 2,5-H2PyDC = 2,5-pyridinedicarboxylic acid, 3-HPyC = 3-pyridinecarboxylic acid). X-ray crystallographic analyses revealed that both complexes are isomorphous and show an interesting topology. Magnetic study indicated the coupling interaction between Ln3+ ions in both complexes is weak.In situ hydrothermal decarboxylation reactions play an important role to form two novel (3D) lanthanide–organic frameworks Ln(2,5-PyDC)(3-Py-C)(H2O) (Ln = Nd, Sm; 2,5-H2PyDC = 2,5-pyridinedicarboxylic acid, 3-HPyC = 3-pyridinecarboxylic acid), which can be specified by the Schläfli symbol (42638) as a 3D {4,4}-connected net.

Two new binuclear radical complexes derived from a new long nitronyl nitroxide ligand, 2-[4-(5-pyrimidyl)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (4-NITPhPyrim), and M(hfac)2 (M2+ = Cu2+, Mn2+; hfac− = hexafluoroacetylacetonato), [Cu(hfac)2(4-NITPhPyrim)]2 · 4H2O (1) and [Mn(hfac)2(4-NITPhPyrim)]2 · 4H2O (2), were synthesized as well as characterized structurally and magnetically. X-ray analysis indicates that 1 and 2 are rectangle-like centrosymmetric dimer M2L2 complexes. Magnetic measurements indicate that there are two types of magnetic exchanges in 1: the ferromagnetic (FM) exchange between the Cu(II) ion and the directly bonded nitroxide unit (J1 = 24.20 cm−1) and the weak FM exchange of Cu–NIT through the pyrimidine and phenyl rings (J2 = 0.62 cm−1). Besides the strong antiferromagnetic (AFM) coupling between the Mn(II) ion and the directly bonded nitroxide unit (J = −87.61 cm−1), there is a weak FM interaction between the two Mn–NIT pairs (θ = 0.39 K) in 2.The new long nitronyl nitroxide radical ligand, 2-[4-(5-pyrimidyl)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (4-NITPhPyrim), was successfully utilized to construct two new cyclic dimer M2L2 magnetic complexes [Cu(hfac)2(4-NITPhPyrim)]2 · 4H2O (hfac− = hexafluoroacetylacetonate) (1) and [Mn(hfac)2(4-NITPhPyrim)]2 · 4H2O (2).

A new dinuclear manganese(II)–azido complex: [Mn(2,2′-dpa)(N3)2]21 (2,2′-dpa = 2,2′-dipicolylamine) has been synthesized solvothermally. X-ray crystallography analysis reveals that it consists of two crystallographically independent dimeric manganese moieties; each manganese(II) atom is coordinated by one 2,2′-dipicolylamine, one terminal azido ligand, and double end-on bridging azido ligands, exhibiting a slightly distorted octahedral sphere. There are extensive short contacts among dimeric manganese moieties, which extend the structure into an interesting three-dimensional supramolecular array. Magnetic determination of 1 indicates that dominant ferromagnetic interaction and weak antiferromagnetic interaction, which are ascribed to the end-on azido bridges and the short contacts, respectively, co-exist in this complex.The complex [Mn(2,2′-dpa)(N3)2]2 has been solvothermally prepared and structurally characterized (2,2′-dpa = 2,2′-dipicolylamine). Two manganese centers are connected with each other through double end-on-azido bridges in this dinuclear complex. Each manganese atom is coordinated by one 2,2′-dipicolylamine, double end-on azido ligands and one terminal azido ligand to form a slightly distorted tetrahedral geometry. The extensive short contacts among dimeric manganese molecules play an important role in stabling the crystal structure. This complex exhibits dominant ferromagnetic interaction and weak antiferromagnetic interaction mediated by the end-on azido bridges and the short contacts, respectively.

A three-dimensional (3D) dysprosium(III) metal-organic framework with nicotinate N-oxide (NNO–) and squarate (C4O42–) mixed bridging ligands, [Dy(NNO)(C4O4)(H2O)]n (1), has been hydrothermally synthesized. The dysprosium(III) ions are linked to each other by the squarate anions to form a unique dysprosium(III) squarate double-layered network; the NNO– anions then bridge such layers to complete the 3D framework. Complex 1 exhibits a two-step relaxation of magnetization under a dc field of 1000 Oe, with effective energy barrier values of 8.5 and 14.3 K, respectively.Topics: Crystal structure; Ligands (Organomet.); Magnetic processes; Mechanical properties; Molecular structure;

A new family of 3d–4f heterometallic trinuclear complexes, namely [M2LnL2]·2ClO4·H2O (H3L = tris(((2-hydroxy-3-methoxybenzy1)amino)ethyl)amine, where M = Ni, Ln = Gd (1), Dy (2), and M = Zn, Ln = Gd (3), Dy (4)) were synthesized via the reaction of H3L and Ln(NO3)3·6H2O and Ni(ClO4)2·6H2O or Zn(ClO4)2·6H2O in a 2:1:2 ratio in the solution. Complexes 1–4 consisted of three metal ions arranged in an isosceles triangle manner. Magnetic properties investigations showed that complexes 1 and 2 exhibited weak ferromagnetic coupling between the Ni(II) and Ln(III) ions, whereas complex 4 displayed lanthanide single-ion magnetic properties. The alternating current (ac) magnetic susceptibilities of 4 revealed that both the in-phase (χ′) and out-of-phase (χ′′) signals are frequency- and temperature-dependent, which are typical features of the field-induced slow relaxation of the magnetization with Ueff = 124.5 K. Complex 4 also exhibited an obvious butterfly-shaped hysteresis loop at 2 K, indicating that it is a single-ion magnet. Moreover, complex 4 showed stronger fluorescent emissions, which were typical narrow emission bands of lanthanide ions. Therefore, complex 4 can be considered as a molecular magnetic and luminescent material. Comparably, complex 2 showed very weak DyIII-based emissions because the paramagnetic NiII ions quench the fluorescence and thereby lower the population of the triplet state.

6-Hydroxypyridine-3-carboxylic acid (6-HOPy-3-CO2H) reacts with Ln2O3 (Ln = Nd, Sm, Eu, Gd) and oxalic acid (H2OX) under hydrothermal conditions to generate four novel lanthanide–organic coordination polymeric networks [Ln2(1H-6-Opy-3-CO2)2(OX)2(H2O)3]·2.5H2O (Ln = Nd, 1; Sm, 2; 1H-6-Opy-3-CO2− = 1-hydro-6-oxopyridine-3-carboxylate) and [Ln(1H-6-Opy-3-CO2)(OX)(H2O)2]·H2O (Ln = Eu, 3; Gd, 4). The new co-ligand 1H-6-Opy-3-CO2− anion was generated by the autoisomerization of the single deprotonated 6-HOPy-3-CO2− anion (from the enol form into the ketone one). 1 and 2 are isomorphous, they possess a three-dimensional architecture constructed from Ln3+ ions bridged by oxalate anions and two types of 1H-6-Opy-3-CO2− bridges, showing a three-nodal (4,5)-connected topology (3.42.52.63.7.8)2(3.53.62)2(32.6.72.8) or a simplified uninodal 6-connected topology (33.46.55.6), both topologies are completely new; while only one type of 1H-6-Opy-3-CO2− bridge is used to construct the two-dimensional layer networks of 3 and 4 besides oxalate bridges, both complexes 3 and 4 are isostructural, exhibiting the honeycomb topology 63. The lanthanide contraction effect is believed to play a key role in directing the formation of a particular structure. A magnetic study of 1–3 indicated that the coupling interaction between Ln3+ ions is weak.

The screw propeller-like cluster complex [Mn3(OMe)(LSchiff)3(H2O)Cl2]·2H2O {H2LSchiff = 2-[(E)-(R)-1-hydroxypropan-2-ylimino]methyl-6-methoxyphenol} is the first chiral triangle manganese cluster compound. It is also a rare nonsymmetrical triangle compound with an unequilateral arrangement of three manganese(III) atoms. Both ferromagnetic and antiferromagnetic interactions exist between the Mn3+ ions, exhibiting a magnetic anisotropy.

The structures and properties of two mononuclear Dy(III) enantiomeric pairs were dramatically controlled by crystallization temperature; the enantiomeric pair with coordinated chiral N,N′-donor ligands exhibits enhanced single-ion magnetic, ferroelectric and chiroptical properties with respect to the other one with protonated chiral N,N′-donor ligands.

Reaction of the chiral ligand (−)-4,5-pinenepyridyl-2-pyrazine (L) with Ln(hfac)3·2H2O precursors [hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonate, Ln = Sm3+ (1), Eu3+ (2), Tb3+ (3) and Dy3+ (4)] in methanol solution led to the formation of four noncentrosymmetric lanthanide complexes with the general formula [Ln(hfac)3L]n·H2O. The single-crystal X-ray diffraction analyses revealed that they are isostructural and take a one-dimensional (1D) chain structure based on the Ln(hfac)3L repeating units, in which the nine-coordinate Ln3+ ions reside in a tricapped trigonal prism (TTP) environment never reported in previous 1D chain lanthanide complexes. The investigations of their photophysical properties showed that complexes 1, 2 and 3 exhibit characteristic emissions of Sm3+, Eu3+ and Tb3+ ions with respective luminescent lifetime values of 0.065, 1.066 and 0.129 ms, while complex 4 does not display any emission. The different luminescent intensities and lifetimes among them were further discussed in detail. Moreover, the magnetic properties of complexes 1–4 were assessed with a special emphasis on the Dy3+ complex 4. Alternating-current (ac) magnetic susceptibility measurements indicated that field-induced two-step slow magnetic relaxation processes were observed in 4, indicating the single-molecule magnet (SMM) behavior of 4. In addition, the noncentrosymmetric complexes 1–4 crystallizing in the same polar point group (Cs) exhibit both ferroelectric and nonlinear optical properties at room temperature. All these features make them multifunctional crystalline molecule materials.

Two second-order nonlinear optically (NLO)-active dinuclear and square Cu(II) enantiomeric pairs were obtained via the self-assemblies of enantiopure linear bis-bidentate ligands with different copper(II) salts under the identical reaction conditions. Their magnetic properties are switched from antiferromagnetic to ferromagnetic coupling.

Two novel coaxial double-screw-propeller heptanuclear 3d–4f cluster complexes are ferromagnetic: one exhibits a large magnetocaloric effect while the other a magnetic relaxation behavior, depending on the lanthanoid ions used.

A novel 3D MOF based on dysprosium(III) oxalate and 1,10-phenanthroline (phen), {[Dy(C2O4)1.5phen]·0.5H2O}n (1), has been hydrothermally synthesized. The Dy3+ ion acts as a typical Y-shaped node, linking to each other to generate an interesting 3D topology structure. Complex 1 is the first 3D DyMOF displaying both ferromagnetic coupling and field-induced two-step magnetic relaxation.

An alkoxido-bridged tetranuclear Dy(III) complex, [Dy4(H3L)2(OAc)6]·2EtOH {1, H6L = 1,3-bis[tris(hydroxymethyl)methylamino]propane}, has been solvothermally synthesized and characterized. An X-ray crystallographic study revealed that complex 1 possesses a novel “parallelogram” [Dy4(OCH2–)4] core, and a new binding mode η3:η3:η1:η1:η1:η2:μ4 of the Bis-tris propane ligand was observed. Magnetic investigations indicated that it is a single-molecule magnet (SMM), showing two distinct magnetic relaxation processes with the energy barriers of 44 K and 107 K, respectively. Such a two-step magnetic relaxation process could be well described by the sum of two modified Debye functions.

A new family of 3d–4f dinuclear complexes derived from a chiral Schiff-base ligand, (R,R)-N,N′-bis(3-methoxysalicylidene)cyclohexane-1,2-diamine (H2L), has been synthesized and structurally characterized, namely, [Cu(L)Ln(NO3)3(H2O)] (Ln = Ce (1) and Nd (2)), [Cu(L)Sm(NO3)3]·2CH3CN (3) and [Cu(L)Ln(NO3)3] (Ln = Eu (4), Gd (5 and 5′), Tb (6 and 6′), Dy (7 and 7′), Ho (8), Er (9) and Yb (10)). Structural determination revealed that these complexes are composed of two diphenoxo-bridged CuII–LnIII dinuclear clusters with slight structural differences. Complexes 1, 2 and 4–7 crystallize in the chiral space group P1, and the space group of 3 is P21, while the other six complexes (5′–7′ and 8–10) are isomorphous and each of them contains two slightly different CuII–LnIII dinuclear clusters in the asymmetric unit with the chiral space group P21. Magnetic investigations showed that ferromagnetic couplings between the CuII and LnIII ions exist in 5–7 and 5′–7′. Moreover, the alternating current (ac) magnetic susceptibilities of 6, 6′, 7 and 7′ showed that both the in-phase (χ′) and out-of-phase (χ′′) are frequency- and temperature-dependent with a series of frequency-dependent peaks for the χ′′, which being typical features of field-induced slow magnetic relaxation phenomena. For 8, a frequency dependent χ′ with peaks but χ′′ without peaks appeared; however, the compound displays field-induced slow magnetic relaxation behavior. Furthermore, no obvious frequency-dependent ac signal was observed in 9 owing to the absence of the easy-axis anisotropy. More significantly, we observed the temperature-controlled reversible conversion from one chiral single-crystal (5–7) to another chiral single-crystal (5′–7′) exhibiting slow magnetic relaxation.

Reactions of DyCl3·6H2O or Dy2O3 with 2-quinolinecarboxylic acid (H-QLC) yielded two compounds, namely, [Dy4(QLC)12(H2O)6]·4H2O (1) and [Dy(QLC)3(H2O)2]n (2). Compound 1 is a linear tetranuclear structure with one central [Dy2(QLC)4(H2O)4] subunit and two terminal [Dy(QLC)3(H2O)] subunits linked by bridging QLC− ligands. Compound 2 has a one-dimensional (1D) chain wherein the [Dy(QLC)2] unit formed by two QLC− ligands chelating a Dy(III) ion is connected by the bridging QLC− ligands. Compounds 1 and 2 exhibit slow magnetic relaxation behaviour in the absence of a static magnetic field, which is rarely observed in lanthanide-carboxylate compounds. During the structural evolution from a linear Dy4 cluster of 1 into a 1D chain of 2, the anisotropy energy barrier (Ueff) is enhanced from 45.4(2) to 144.2(1) K. Though the Dy(III) centers in 1 and 2 all are eight-coordinated with square antiprismatic coordination environments, the higher energy barrier observed for 2 could be the result of a more favorable crystal field for the Dy(III) ions in 2.

Two isostructural dense lanthanide metal–organic frameworks derived from an extended ligand 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB), [Ln(BTB)H2O]n (Ln = Eu, 1; Ln = Dy, 2), which are constructed via a cross-like folding assembly strategy, were yielded by ‘two-step warming solvothermal synthesis’. Complex 1 shows luminescence while complex 2 exhibits field-induced two-step magnetic relaxation.