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A new organic fluorescent ionic compound [MOBIP]I (1) (MOBIP+ = 1-methyl-2-oxo-3 -(1H-benzimidazol-2(3H)-ylidene)-2,3-dihydropyridinium) was synthesized and used to prepare seven maleonitriledithiolate metal complexes [MOBIP] n [M(mnt)2] by substitution of the iodide ion with [M(mnt)2] n − (M = Cu2+ (2), Ni2+ (3a), Ni3+ (3b), Zn2+ (4), Cd2+ (5), Pd2+ (6), and Pt2+ (7)). An investigation of fluorescence properties shows that these complexes are a new series of solution luminescent complexes of maleonitriledithiolate derivatives with strong blue light fluorescence in daylight by irradiation with UV light with high quantum yields. They display similar symmetric emissions with λem at the deep blue region of ∼426 nm upon excitation at ∼364 nm in DMF, caused by L–L transition of MOBIP+. Existence of [M(mnt)2] n − anions in the solution prolongs the fluorescent lifetimes. For all these compounds in the solid state, the fluorescent emission is blue-shifted and more narrow than that in solution. Based on their crystal structure analysis, the weak stacking interactions in compounds cause the difference of their fluorescence spectrum. Investigations of variable-temperature magnetic susceptibility indicate that 2 has weak antiferromagnetic coupling, while 3b exhibits stronger antiferromagnetic coupling. [ABSTRACT FROM AUTHOR]

Two novel lanthanide coordination polymers, [Eu2(EBTC)(DMF)5(NO3)2]·DMF (1) and [Eu2(BBTC)1.5(CH3OH)2(H2O)2]·7DMF·HNO3(2) (EBTC4−= 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylate; BBTC4−= 1,1′-butadiynebenzene-3,3′,5,5′-tetracarboxylate), were successfully synthesized from conjugated ligands of EBTC4−and BBTC4−. Although the two tetracarboxylate ligands have similar structures, their different rigidity/flexibility results in quite different networks upon complexation. Complex 1has a two-dimensional (2-D) layered structure with two crystallographically independent Eu3+ions, one in a distorted monocapped square-antiprism and the other in a distorted square-antiprism coordination geometry. Complex 2exhibits a three-dimensional (3-D) porous framework, with one type of Eu3+in a distorted square-antiprism and the other in a trigondodecahedron environment. Both 1and 2emit the intensely red characteristic luminescence of Eu3+ion at room temperature, with a long lifetime of up to 1.3 and 0.7 ms, respectively, during which the ligand emission of EBTC4−/BBTC4−was quenched by the Eu3+ion, indicating the existence of efficient energy transfer between the conjugated ligand of EBTC4−/BBTC4−and the Eu3+ion. Thus, both EBTC4−and BBTC4−are ideal ligands with an “antenna” effect for the Eu3+ion. The two complexes show the single-ion magnetic behaviors of Eu3+with strong spin–orbit coupling interactions even if there are shorter distances (5.714 Å for 1versus4.275 and 5.360 Å for 2) between the neighboring Eu3+ions connected by oxygen atoms of the tetracarboxylates. [ABSTRACT FROM AUTHOR]

A low-dimensional compound [C6-Apy][Ni(mnt)2] (1, where mnt2−= maleonitriledithiolate, C6-Apy+= 4-amino-1-hexylpyridinium) has been designed and synthesized, which has layer arrangement of anions and cations and shows two steps of magnetic transitions. The low temperature magnetic transition has an uncommon hysteresis loop, while the crystal structure investigations disclosed no structural transition with the magnetic transition. The high temperature magnetic transition exhibits two remarkable features: (1) it synchronously occurs with a crystalline-to-mesophase transition in the first heating process and (2) the structural changes that accompany the solid-mesophase transition are irreversible. A diamagnetic and isostructural compound, [C6-Apy][Cu(mnt)2], is further characterized by structure, DSC and POM techniques, which revealed also the existence of an irreversible crystalline-to-mesophase transition in the same temperature interval of [C6-Apy][Ni(mnt)2]. Therefore, the high-temperature magnetic transition in 1is driven by release of the structural strains, but not magnetoelastic interactions. The mesophase exhibits the characteristic of smectic A phase, and the alkyl chain melting in the cation layers probably lead to the formation of mesophase. It is noticeable that the finding of a mesophase occurring in a hexyl hydrocarbon chain molecular system is in contrast to a suggested rule that at least a dodecyl chain is required. Our results will shed a light on the design and preparation of a new low-dimensional molecular system combining magnetic transition and liquid crystal properties. [ABSTRACT FROM AUTHOR]

[Ni(hmp)(MeOH)Br]4 ⋅ 2H2O has been prepared by the reaction of 2-hydroxymethylpyridine with NiBr2 ⋅ 3H2O and characterized by IR, elemental analysis, powder X-ray diffraction, thermogravimetric analyses, magnetic measurements, and single crystal X-ray diffraction. The crystal structure shows two independent [Ni(hmp)(MeOH)Br]4 molecules in the asymmetric unit and [Ni4O4]4+ cubane-type cores. Each octahedral Ni(II) is bridged by four μ3-CH2O- fragments from four hmp- ligands. Magnetic studies show that ferromagnetic coupling gives an S = 4 ground state with significant magnetoanisotropy, and the parameters are J1 = 8.56, J2 = 2.28, D = -0.65 cm-1, and g ≈ 2.13. [ABSTRACT FROM AUTHOR]

Two new salts, [2-NaMePy]2[Ni(i-mnt)2] (1) and [2-NaMe-4-MePy]2[Ni(i-mnt)2] (2) ([2-NaMePy]+ = 1-(2'-naphthylmethyl)pyridinium, [2-NaMe-4-MePy]+ = 1-(2'-naphthylmethyl)-4-methylpyridinium and i-mnt2- = iso-maleonitriledithiolate), have been prepared and characterized by elemental analyses, UV, IR, molar conductivity, and single crystal X-ray diffraction. The anions in 1 form a 1-D chain through short C ··· N interactions between the anions, while the cations in 2 stack a 1-D column via C-H ··· π and π ··· π stacking interactions between the cations. The effect of weak intramolecular interactions such as C-H ··· N, C-H ··· S, C-H ··· Ni hydrogen bonds, and π ··· π stacking interactions between the cations and the anions further generate a 3-D network structure. The change of the molecular topology of the countercation when the 4-substituted group in the pyridine ring is changed from H atom to CH3 group results in different crystal system, space group, and the stacking mode of the cations and anions of 1 and 2. [ABSTRACT FROM AUTHOR]

Complexes [Ni(H 2 O) 6 (ML) 2 ]· n H 2 O (M = Cu, Ni; L = Schiff base derived from glycylglycine and salicylaldehyde, C 11 H 9 N 2 O 4 ) were synthesized and characterized. The [Ni(H 2 O) 6 (CuL) 2 ]·10H 2 O complex 1 crystallized in the space group , with a = 7.217(1), b = 11.674(1), c = 12.678(1) Å, α = 66.56(1), β = 76.60(1), γ = 80.46(1)°, and Z = 1. The [Ni(H 2 O) 6 (NiL) 2 ]·2H 2 O complex 2 crystallized in the group P 2(1)/ c , with a = 10.564(2), b = 20.246(4), c = 6.965(2) Å, β = 103.14(1)°, and Z = 2. Hydrogen bonding involving [ML] - , Ni(H 2 O) 6 2+ and molecular water forms a three-dimensional (3D) supermolecule. The determination of variable-temperature magnetic susceptibilities indicates an antiferromagnetic interaction between the metallic atoms of 1 , and a corresponding ferromagnetic interaction for 2 . [ABSTRACT FROM AUTHOR]

The maleo­nitrile moiety of the title compound, (2 Z)-2,3-bis­[(4-nitro­benzyl)­sulfanyl]­but-2-ene­di­nitrile, C18H12N4O4S2, is almost planar. The two benzene rings are nearly parallel to each other and perpendicular to the maleo­nitrile plane. Intermolecular S⃛S and π-π interactions are observed in the crystal structure. [ABSTRACT FROM AUTHOR]

Abstract: 1D spin-Peierls-like complexes assembled from [Ni(mnt)2]− with Λ-shaped 1-(4′-R-benzyl)pyridinium derivatives (R represents a substituent) are reviewed, with data on their crystal structures, magnetic properties under ambient conditions as well as under pressure, and the nature of the paramagnetic-to-nonmagnetic transition. In this series of 1D spin systems, the correlation between the magnetic exchange and the anion stacking pattern is addressed by application of density functional theory (DFT) combined with a broken-symmetry approach. The qualitative relationship between the transition enthalpy change and the variation of the magnetic susceptibility in the low-temperature phase is determined. The influence of nonmagnetic doping on the structural and magnetic properties and the magnetic transitions are reported. Furthermore, the effect of the substituent group in the phenyl ring of the cation on the transition temperature and the origin of the transition are discussed. [Copyright &y& Elsevier]

Abstract: A novel molecular solid, [OFBzIQl][Ni(mnt)2] (1), where [OFBzIQl]+ =1-(2′-fluorobenzyl)isoquinolinium and mnt2− =maleonitriledithiolate, forms 1D column of alternating between cations and anions via π⋯π stacking interaction between Ni(mnt)2 plane and isoquinoline ring, and the Ni(mnt)2 anions between the adjacent columns exist short C⋯N interaction. The extensive hydrogen bonds between anions and cations in the crystal generate a 2D network structure. Magnetic susceptibility measurement for 1 in the temperature range 2.0–300K shows that 1 exhibits a magnetic constant transition from ferromagnetic to antiferromagnetic around 35K as the temperature is lowered. [Copyright &y& Elsevier]

Abstract: A new 3d–4f heterometallic coordination polymer [Gd(H2O)3(NO3 −)(CuL)2] H2O (1) (H3L=glycylglycine, N-[1-(2-hydroxy, phenyl)-propylidene]) has been synthesized and characterized by IR, elemental analysis, TGA and X-ray single-crystal diffraction. In the coordination polymer, two metallo-ligand CuLs are connected with Gd3+ ion to form a 1-D chain via carboxylate and carbonyl oxygen. The neighboring Cu–Gd–Cu chains are further connected by hydrogen bonds to form a two-dimensional structure. Magnetic studies for 1 reveal that ferromagnetic interactions (J CuGd =1.30cm−1) between Cu(II) and Gd(III) centers are operating within the CuII–GdIII–CuII systems. [Copyright &y& Elsevier]

Abstract: A novel coordination polymer 1 {[Zn5(MDIP)2(H2O)6(μ3-OH)2]·2H2O} n has been synthesized using methylenediisophthalic acid (H4MDIP) under hydrothermal conditions. Single-crystal X-ray diffraction analysis indicates that 1 shows a 3D porous framework with two types of 1D channel. The structure is further simplified by topology analysis which indicates a (4, 8)-connected net with a Schläfli symbol of (44.62)2(416.612) topology. Moreover, compound 1 displays a strong blue photoluminescent property. [Copyright &y& Elsevier]

Abstract: Three complexes of [Ni(mnt)2]− (mnt2− =maleonitriledithiolate) with benzylpyridinium derivatives, 1-(2′,6′-dichlorobenzyl)-4-aminopyridinium (abbr. Cl2BzNH2Py+) and 1-(2′,6′-dichlorobenzyl)quinolinium (abbr. Cl2BzQl + ), have been characterized structurally and magnetically. The [Cl2BzNH2Py][Ni(mnt)2] solution in MeCN was slowly evaporated to give the crystals of 2, whilst its solution in i-PrOH/MeCN yields 2·0.5i-PrOH. The [Ni(mnt)2]− anions are arranged in the mixed stacks of anions and cations in 2, and the segregated stacks of anions and cations in 2·0.5i-PrOH and 4. Even though three complexes exhibit different stacking pattern of magnetic anions, their temperature dependences of magnetic susceptibilities in 2–300K range show a common feature, namely, two broad maxima of magnetic susceptibility. Powder X-ray examination for three complexes excluded that the impurity causes such complicated magnetic behaviors. Combined with the single crystal structure analyses, the double broad maxima of magnetic susceptibility is probably attributed to anisotropic magnetic exchange interactions between magnetic anions. [Copyright &y& Elsevier]

Abstract: Hydrothermal reactions between H4ODPA (2,2′,3,3′-oxydiphthalic acid) and metal ion salts of Ba2+, Cu2+, Zn2+ and Gd3+ afford four novel coordination polymers [Ba(H2ODPA)(H2O)4]·H2O (1), [Cu2(ODPA)(H2O)3]·H2O (2), Zn2(ODPA)(H2O)2 (3) and [Gd(HODPA)(H2O)3.5]·H2O (4), accordingly. These polymers show great differences in regard to their structures and properties originated from the variation of size and coordination geometry of the metal ions. Compound 1 presents puckered achiral layer structure with (4.82) topology with helices, 2 has a 63 topology with copper tetramer as SBUs, 3 has chiral layer with two kinds of helices built up from Zn-binuclear “paddle-wheel” like SBUs, and 4 features a simple 1D helix with opposite chirality. Compound 3 shows obvious fluorescent emissions upon excitation. Compound 2 shows ferromagnetic interactions between CuII centers bridged by carboxylate groups, whereas compound 4 presents weak ferromagnetic interaction between GdIII ions. [Copyright &y& Elsevier]

A new ion-pair complex, [BzTPP]2[Ni(i-mnt)2](1) (i-mnt2- = iso-maleonitriledithiolate, [BzTPP]+ = benzyltriphenylphosphinium) was synthesized and characterized by elemental analysis, IR, UV, EI-MS spectra and single crystal X-ray diffraction. The single-crystal structural analysis shows that 1 crystallizes in the triclinic space group P-1, with a = 9.466(1) Å, b = 10.196(1)Å, c = 29.252(3)Å, α = 99.28(1)ˆ, β = 93.96(1)ˆ, γ = 106.34(1)ˆ, V = 2654.3(4)Å3, Z = 2. The Ni(II) ions of the [Ni(i-mnt)2]2 - anion adopted a square-planar coordination geometry. Four weak C─H...N hydrogen bonds between the anions and the cations observed in the crystal give further rise to a 3D structure. [ABSTRACT FROM AUTHOR]

Abstract: Three new ion-pair complexes, consisting of 1-benzyl-4-aminopyridinium with [M(mnt)2]2− where mnt2− =maleonitriledithiolate and M=Ni2+, Pd2+ or Pt2+ for complexes 1–3, have been synthesized and structurally characterized. X-ray single crystal studies revealed that three complexes are isostructural and crystallize in monoclinic space group C2/c, and there exist weak H-bonding interactions between –NH2 groups of cation and –CN group of anion as well as weak M…H-bonding interactions between anions and cations. The calculations of charge density distribution disclosed that the M…H-bonding interaction in crystals of 1–3 is mainly attributed to static electric interactions. Two types of H-bonding interactions lead to the formation of two-dimensional sheet structure which is parallel to the crystallographic bc-plane in the crystals of 1–3. A near-IR absorbance appears in the UV–vis-NIR spectra of 1 and 3, respectively, while does not come out in the spectra of 2. [Copyright &y& Elsevier]

Abstract: Two new molecular magnets, [RBzPyN(CH3)2][Ni(mnt)2] [mnt2−=maleonitriledithiolate; [RBzPyN(CH3)2]+=1-(4′-R-benzyl)-4-dimethylaminopyridinium; R=CN(1), F(2)], with unusual magnetic properties have been prepared and characterized. Both 1 and 2 form a 3D network structure in which the [Ni(mnt)2]− anions form a 1D magnetic chain for 1 and a stepwise stack for 2 via weak π…π stacking interactions, C…C or C…N short interactions between the neighboring anions. Magnetic susceptibility measurements in the temperature range 1.8–300K indicated that 1 and 2 show unusual spin gap transition around 30K and 110K, respectively. The transition for 1 and 2 is the second-order phase transition as determined by the capacity measurement. [Copyright &y& Elsevier]

Abstract: Two novel coordination polymers, [Cu(PDCO)·(H2O)] n (1) and [Cd(PDCO)(bipy)·(H2O)·5H2O] n (2), (H2PDCO=pyridine-3,5-dicarboxylic acid N-oxide, bipy=4,4′-bipyridine), have been synthesized under hydrothermal conditions, and their structures were determined by single-crystal X-ray diffraction studies. Polymer 1 features a three-dimensional (3D) network with nonequivalent nodes of (63)2(69 ·85 ·10) topology. Polymer 2 exhibits one-dimensional (1D) double-stranded chains. The magnetic character of 1 as well as the gas adsorption and luminescent properties of 2 have been investigated. [Copyright &y& Elsevier]

Abstract: Five new interesting transition metal coordination polymers [MnL2(bpy)2(H2O)2] n (1) (H2L=4-carboxymethylbenzoic acid) (bpy=4,4′-bipyidine), [CoL(bpy)(H2O)3 ·H2O] n (2), [CdL(bpy)(H2O)3 ·H2O] n (3), [Cu2L(bpy)2 ·3H2O] n (4) and [Zn2L2(bpy)·H2O] n (5) have been synthesized under solvothermal conditions and structurally characterized. This series of complexes has shown an intriguing variety of architectures, which firstly form zero- to two-dimensional frameworks by metal–ligand interactions, and secondly form three-dimensional supramolecular frameworks by intermolecular interactions such as hydrogen bonds. Compound 3 shows strong blue fluorescent emissions in the solid state upon photo-excitation at 359nm at room temperature and may be an excellent candidate for blue-fluorescent materials. Compound 4 appears to be a good candidate for new hybrid inorganic–organic NLO materials. [Copyright &y& Elsevier]

Abstract: Three silver complexes Ag2(L)2(NO3)2 (1), Ag2(L)2(SO3CF3)2(H2O)0.5 (2), and [Ag2(L)2(NO3)2] n (3) were prepared from molecular clips, 2,2′-Bis(imidazol-1-ylmethyl)-biphenyl (L) and structurally characterized to investigate the structural-luminescent relation. Compound 1 is a bimetallic supramolecular rectangle in which two L ligands are connected by two linearly coordinated Ag(I) ions. Compound 2 is described as a double helicate due to the nature of the twist of the imidazole groups after coordination to Ag(I) centers. In compound 3, the Ag(I) centers are connected by L ligands into a one-dimensional zigzag chain. Solid state and solution fluorescent measurements exhibit the presence of ligand-based emission at 415 and 435nm of compounds 1 and 2, respectively. It is said that the dihedral angles between the two imidazole rings coordinated to one Ag(I) center affect the emission properties. [Copyright &y& Elsevier]

Abstract: Two novel heterotrinuclear Cu(II)-M(II)-Cu(II) (M=Ni and Mn) complexes, [Ni(H2O)4(CuL)2]·7H2O (1), [Mn(H2O)4(CuL)2]·8H2O (2), have been obtained by the self-assembly of the mononuclear tripeptide Schiff base complexes [CuL]− with bivalent metal ion M2+, where H3L=N-salicylideneglycylglycylglycine. Single crystal X-ray diffraction experiments indicate that the structures both 1 and 2, are made up of centrosymmetric trinuclear units with the M atom lying on an inversion center, formed the 1D supramolecular chain structures via hydrogen bondings and M⋯O weak interactions. The magnetic susceptibility data (2–300K) revealed antiferromagnetic interactions between copper(II) ions and the central metal. The magnetic susceptibility data were quantitatively analyzed using the theoretical expressions deduced from the spin Hamiltonian for a symmetrical three-spin system to give the coupling parameters J CuNi=−0.46cm−1 and J CuMn=−0.15cm−1. [Copyright &y& Elsevier]

Two copper(II) tripeptide Schiff base complexes: [Mg(H2O)6][CuL]2 · 3.5H2O (1) and [Cd(H2O)4(CuL)2] · 3.5H2O (2) (H3L=N-salicylideneglycylglycylglycine) have been synthesized and structurally characterized. Single crystal X-ray diffraction analyses showed that the copper atom exhibits square-planar geometry, with the chelating ONNO atoms of the deprotonated Schiff base ligand(L) in the basal plane. In 1, the anions [CuL]− and cations [Mg(H2O)6]2+ are stacked in well-separated columns along the a-axis. In 2, two symmetric [CuL]− groups coordinate to Cd(II) at an inversion center, each via one carboxylate oxygen atom, to form a heterotrinuclear complex. Variable-temperature magnetic susceptibility measurements revealed the occurrence of an antiferromagnetic interaction in 1 and 2. [Copyright &y& Elsevier]

Heteropolynuclear organometallic compounds have been constructed by using two kinds of ferrocene-based ligands, 1,1'-ferrocenedicarboxylic acid (H[sub 2]L¹) and ferrocenecarboxylic acid (HLsup2;). Reactions the ligand H[sub 2]L¹ with copper(II) and nickel(II) salts, in the presence of pyridine, give a tetranuclear Cu[sub 2]Fe[sub 2] mixed-metallic box Cu[sub 2]L¹[sub 2](PY)[sub 2](DMF)[sub 2](H[sub 2]O)[sub 2] (1) and a tetranuclear heterobimetallic helix Ni[sub 2]L¹[sub 2](Py)[sub 4](H[sub 2]O) (2), respectively. In these complexes, the ferrocene moieties show cisoid conformations which lead to the formation of the finite coordination geometry, i.e. to molecular complexes. Interactions of the ligand H[sub 2]L¹ with lanthanide ions afford two-dimensional networks [La[sub 2]L¹[sub 3](CH[sub 3]OH)[sub 4]]∞ (3), [Eu[sub 2]L¹[sub 3](H[sub 2]O)[sub 5]][sub ∞] (4), and [Gd[sub 2]L¹[sub 3](CH[sub 3]OH)[sub 2](H[sub 2]O)[sub 3]][sub ∞] (5), respectively, in which transoid conformations of the ferrocene moiety provide opportunities to form infinite 2-D networks. It is suggested that the conformational freedom of the ferrocene moiety makes the ligand L¹ display different conformations and coordination modes in these complexes. In addition, the π···π interactions related to the ferrocene moieties were also found to stabilize the supramolecular architectures in the solid state. As a comparison, reaction of lanthanide ions with the ligand HL² resulted in three isostructural heterodinuclear windmill-shaped compounds Ln[sub 2]L²[sub 6](CH[sub 3]OH)[sub 2](H[sub 2]O)[sub 5] [Ln = La (6), Eu (7), and Gd (8)] by simply diffusing the solutions of lanthanide ions into the mixture of HL² and NaOH, respectively. Electrochemical properties of the ferrocene-containing complexes 1-8 are also investigated in the solution or solid state. [ABSTRACT FROM AUTHOR]

Two new ion-pair complexes [1-(4′-fluorobenzyl)pyridinium][Ni(bdt)2] (1) and [1-(4′-bromobenzyl)pyridinium][Ni(bdt)2] (2), in which bdt2−=1,2-benzenedithiolate (‘S2’2−), have been prepared and characterized. X-ray structural analyses showed that 1 and 2 are isostructural, and the anions are centrosymmetric. The 2 non-equiv. anions form different uniform-spaced stacking pattern in 1 and 2. The magnetic measurements of 1 and 2 indicate ferromagnetic behavior in the antiferromagnetic exchange system, which may arise from spin canting. Cyclovoltammetry revealed two quasi-reversible one-electron steps for 1 and 2, which are attributed to Ni(IV/III) and Ni(III/II) redox couples. [Copyright &y& Elsevier]

Abstract: An ion-pair complex of [Ni(mnt)2]2− with p-N-benzylpyridinium α-nitronyl nitroxide radical cations (p-BzPYNN) in acetonitrile shows a moderate and broad absorbance in near-IR region. In the crystal of this complex, two radical cations form a dimer via strong H-bonding interaction; such kinds of dimers are connected into H-bonding chain by [Ni(mnt)2]2− dianions through weak H-bonding interactions. The neighboring H-bonding chains are arranged into supramolecular sheet via π…π stacking interactions between the five-membered chelate-ring of anion and the superimposed pyridyl rings of cations. The polycrystalline EPR spectrum exhibits two isotropic EPR signals. Based on the analyses of crystal structure, variable temperature magnetic susceptibility and electronic spectrum, the stronger EPR signal is assigned to the radical cation, the weaker one probably arises from a trace amount of [Ni(mnt)2]1− species. [Copyright &y& Elsevier]

Abstract: A charge-transfer compound, [NO2BzPz][Ni(mnt)2] (NO2BzPz+ =1-(4′-nitrobenzyl)pyrazinium and mnt2− =maleonitriledithiolate), has been structurally characterized, which shows rare noncovalently intermolecular interactions between lone-pair electron and electron-deficient pyrazine rings (NO2⋯π and CN⋯π), theoretical analysis reveals that such intermolecular interactions can be attributed to Coulomb interaction. The paramagnetic [Ni(mnt)2]− anions in [NO2BzPz][Ni(mnt)2] form a dimerized stack and strong antiferromagnetic coupling interaction is observed in such a spin dimer which lead to weak paramagnetic feature in this compound. [Copyright &y& Elsevier]

Abstract: Two isostructural bimetallic tetranuclear chiral complexes, [K(18-crown-6)]3[Fe(ox)3]·9H2O and [K(18-crown-6)]3[Cr(ox)3]·9H2O, crystallize in rhombohedral R3 space group, the tetranuclear cluster is respectively built from one [Fe(ox)3]3− or [Cr(ox)3]3− species with three K(18-crown-6 ether) supramolecular cations linked by oxalate groups, and lattice water molecules form the double helical chains. Two complexes are second-harmonic-generation (SHG) active with the SHG response about 0.5 times that of urea. [Copyright &y& Elsevier]