Bix Ligands Research Articles

Regulation of Structure and Magnetic Properties for Nickel(II)/Cobalt(II) Coordination Polymers with 1,4‐Bis(imidazole‐1‐ylmethyl)benzene Ligand

AbstractTwo new coordination polymers Ni(bix)3 ⋅ 2(NO3) ⋅ (H2O) 1 and Co(bix)2 ⋅ 2(NO3) 2 (bix=1,4‐bis(imidazole‐1‐ylmethyl)benzene) have successfully been synthesized via hydrothermal reactions. These two compounds have similar local coordination environments but different topological networks due to the flexibility of the bix ligand. Additionally, magnetic studies reveal that 1 and 2 also exhibit different magnetic behaviors. Although magnetic exchange pathways are same as MII‐bix‐MII (M=Ni 1, Co 2), 1 shows purely paramagnetic state almost down to 2 K with weak antiferromagnetic interaction; while stronger antiferromagnetic interaction in 2 is suggested. Meanwhile, an anomaly around 38 K in zero‐field‐cooled mode is observed but suppressed in field‐cooled mode, which may be suggesting the spin canting for 2. The field dependent magnetizations show magnetization of 2.17 μB and 2.44 μB at 7 T for 1 and 2, respectively. Also, the magnetic interaction J/kB of −3.3 K is estimated for 2.

Band gap, sorption properties and fluorescence sensing behaviour of a novel 1D→2D cathenane-like cobalt(II)-organic framework.

A novel hydrolytic stable CoII-organic framework, namely poly[[bis(2-amino-4-sulfonatobenzoato-κO1)tetraaquatris{μ-1,4-bis[(imidazol-1-yl)methyl]benzene-κ2N3:N3'}dicobalt(II)] tetrahydrate], {[Co(C7H5NO5S)(C14H14N4)1.5(H2O)2]·2H2O}n, (1), based on multifunctional 2-amino-5-sulfobenzoic acid (H2asba) and the auxiliary flexible ligand 1,4-bis[(imidazol-1-yl)methyl]benzene (bix), was prepared using the solution evaporation method. The purity of (1) was confirmed by elemental analysis and powder X-ray diffraction (PXRD) analysis. Complex (1) shows a novel 1D→2D interpenetrating network, which is further extended into a 3D supramolecular framework with channels occupied by the lattice water molecules. The 2-amino-4-sulfonatobenzoate (asba2-) ligand adopts a monodentate coordination mode. The bix ligands exhibit gauche-gauche (GG) and trans-trans (TT) conformations. A detailed analysis of the solid-state diffuse-reflectance UV-Vis spectrum reveals that an indirect band gap exists in the complex. The band structure, the total density of states (TDOS) and the partial density of states (PDOS) were calculated using the CASTEP program. The calculated band gap (Eg) matches well with the experimental one. The complex exhibits a reversible dehydration-rehydration behaviour. Interestingly, gas sorption experiments demonstrate that the new fully anhydrous compound obtained by activating complex (1) at 400 K shows selective adsorption of CO2 over N2. Complex (1) retains excellent framework stability in a variety of solvents and manifests distinct solvent-dependent fluorescence properties. Moreover, the complex shows multiresponsive fluorescence sensing for some nitroaromatics in aqueous medium.

Preparation and characterization of two new CuII supramolecular coordination polymers incorporating sulfobenzoate and flexible heterocyclic ligands.

The assembly of CuII with the multifunctional ligand 2-amino-4-sulfobenzoic acid (H2asba) in the presence of the auxiliary flexible ligands 1,4-bis(triazol-1-ylmethyl)benzene (bbtz) and 1,4-bis(imidazol-1-ylmethyl)benzene (bix) under ambient conditions resulted in two new supramolecular coordination polymers, namely poly[[(3-amino-4-carboxybenzenesulfonato-κO)aquabis[μ2-1,4-bis(triazol-1-ylmethyl)benzene-κ2N4:N4']copper(II)] 3-amino-4-carboxybenzenesulfonate tetrahydrate], {[Cu(C7H6NO5S)(C12H12N6)2(H2O)](C7H6NO5S)·4H2O}n, (1), and poly[[bis(μ2-2-amino-4-sulfonatobenzoato-κ3O1:N,O1')tetraaqua[μ2-1,4-bis(triazol-1-ylmethyl)benzene-κ2N4:N4']dicopper(II)] tetrahydrate], {[Cu2(C7H5NO5S)2(C14H14N4)(H2O)4]·4H2O}n, (2). Single-crystal X-ray structure diffraction analysis of (1) reveals that the bbtz ligand acts as a bridge, linking adjacent CuII ions into a two-dimensional cationic (4,4) topological network, in which the coordinated 3-amino-4-carboxybenzenesulfonate (Hasba-) anion uses its sulfonate group to bind with the CuII ion in a monodentate fashion and the carboxylate group remains protonated. The lattice Hasba- anion resides in the two-dimensional layer and balances the charge. The carboxylate group of the 2-amino-4-sulfonatobenzoate (asba2-) ligand in (2) is involved in bidentate coordination, connecting adjacent CuII ions into carboxylate-bridged chains which are further bridged by the auxiliary flexible bix ligand in a trans-gauche (TG) mode, resulting in the formation of a two-dimensional network architecture. The amino group of the asba2- ligand in (2) also takes part in the coordination with the central CuII ion. The six-coordinated CuII centres in (1) and (2) exhibit distorted octahedral coordination geometries. Extensive hydrogen bonding exists in both (1) and (2). The interlayer hydrogen bonds in both compounds further extend adjacent two-dimensional layers into three-dimensional supramolecular network architectures. Furthermore, a detailed analysis of the solid-state UV-Vis-NIR (NIR is near IR) diffuse reflectance data indicates that (1) and (2) may have potential as wide band gap indirect semiconductor materials. Compounds (1) and (2) show reversible and irreversible dehydration-rehydration behaviours, respectively.

Structural diversity of four coordination polymers based on 5-nitro-1,2,3-benzenetricarboxylic acid (H3nbta): Solvothermal syntheses, structural characterizations and properties

Four 3D coordination compounds, named [Cd3(nbta)2(bix)2(H2O)2]·H2O (1), Zn3(nbta)2(biim)3 (2), Zn6(nbta)4(btd)5 (3) and [Co3(nbta)2(bid)(H2O)8]·4H2O (4) (bix=1,4-bis(imidazole-1-ylmethyl)benzene, biim=1,1′-(1,4-butanediyl)bis(imidazole), btd=1,10-bis(1,2,4-triazol-1-yl)decane, bid=1,10-bis(imidazole-1-yl)decane), and H3nbta=5-nitro-1,2,3-benzenetricarboxylic acid), have been synthesized by solvothermal methods and structurally characterized by X-ray diffraction studies. In compound 1, every nbta3- anion connects four CdII ions to give a 2D layer, and the layers are pillared by bix ligands to generate a 3D framework with a Schläfli symbol of (3·4·63·7)(4·64·8)(43·63)(34·42·66·76·88·92). For compound 2, every nbta3- anion connects three ZnII ions to give a 2D layer structure, the 2D layers are further connected into a facinating 3D framework by biim ligands with (3,4)-connected (3·6·7)(3·5·62·7·8)(3·52·6·8·9)(5·6·8·10·112) topology. In compound 3, the nbta3- anions are connected by ZnII ions to generate a 2D layer, and the layers are bridged by btd ligands to build a fascinating 3D framework with (4·6·7·8·92)(4·6·8·92·10)(4·93·102)(4·6·8·9·102)(4·6·7·8·9·10)(4·6·7·8·102)(42·6·7·8·9) topology. In compound 4, the nbta3- aions are connected by CoII ions into a 2D layer, the 2D layers are linked by bid ligands to generate a 3D 103 topological framework. Furthermore, the IR spectra, TGA, PXRD, elemental analyses, the solid-state luminescence of compounds 1–3 have been studied.

Mixed-ligand cobalt, nickel and zinc coordination polymers based on flexible 1,4-bis((1H-imidazol-1-yl)methyl)benzene and rigid carboxylate linkers

The mixed-ligand coordination polymers {[Zn(BIX)2.5](NO3)2·5.5H2O}n (1), {[Co(BIX)(HBTC)](BIX)0.5·H2O}n (4), [Ni(BIX)2(BDC)(H2O)]n (5), [Zn(BIX)(PDC)]n (6), [Ni(BIX)(PDC)(H2O)]n (7) and [Zn(BIX)0.5(HIDC)]n (8) were synthesized, structurally characterized and compared to the known coordination polymers {[Co(BIX)3](NO3)2·4H2O}n (2) and {[Zn2(BIX)(BTC)(OH)]·H2O}n (3) to determine the mutual influence of an anionic carboxyl ligand and a neutral N-donor ligand (BIX=1,4-bis((1H-imidazol-1-yl)methyl)-benzene; H3BTC=1,2,3-benzene-tricarboxylic acid; H2BDC=1,3-benzene-dicarboxylic acid (isophthalic acid); H2PDC=3,4-pyridine-dicarboxylic acid; H3IDC=4,5-imidazole-dicarboxylic acid). Compound 1 is a 1D ladder-like structure with two bridging and one terminal (dangling) BIX ligand. Neighboring ladders mutually entangle with the dangling BIX ligand being threaded through {Zn4(BIX)4} openings from adjacent strands. Compound 2 shows a 3D pcu-network with octahedrally coordinated cobalt ions bridged by three crystallographically different inversion-symmetric BIX ligands. The overall structure motifs in the mixed-ligand compounds are 1D metal-carboxylate chain-structures, bridged by neutral BIX ligands to form either 1D ladder-like strands (4), 2D networks (3, 5 with square lattice, 4,4 or sql topology, 7, 8 with honeycomb, 6,3 or hcb topology) or 3D frameworks (6 with diamond, 6,6 or dia topology). Noteworthy, compound 4 forms a 1D tubular structure of stacked {Co2(BIX)2} metallacycles that are threaded with uncoordinated BIX ligands like a rotaxane. A tetrahedral asymmetric Zn atom is formed in the crystals of 6 with spontaneous resolution as only one Zn configuration assembles into the 3D chiral framework of each single crystal.

ChemInform Abstract: Coordination Polymers Built from 1,4‐Bis(imidazol‐1‐ylmethyl)benzene: from Crystalline to Amorphous

AbstractReview: 85 refs.

A New Luminescent Zn(II) Coordination Polymer Constructed From Oxalate and Imidazol-Based Ligands

A new Zn(II) compound, namely [Zn3(oxa)3(bix)3]n (1 H2oxa = oxalic acid, bix = 4,4′-bis(imidazol-1-ylmethyl)benzene), has been synthesized by the reactions of Zn(II) ions with H2oxa and bix ligands under hydrothermal conditions. Single-crystal X-ray analysis reveals that compound 1 features a 2D layer framework, which further extended into a 3D supramolecular framework via intermolecular hydrogen bonds. In addition, the luminescent property of 1 was also investigated in the solid state at room temperature.

Nitrate Ions Templated 3D Noninterpenetrating 6-Connected pcu Net: Synthesis, Structure and Properties

A new Co(II) coordination polymer, namely [Co0.5(bix)1.5]n·n(NO3)·2n(H2O) (1 bix = 4,4′-bis(imidazol-1-ylmethyl)benzene), has been successfully synthesized and structurally characterized. Single-crystal X-ray analysis reveals that the crystal belongs to triclinic crystal system, P-1 space group with a = 9.3078(9), b = 9.9938(10), c = 13.2647(14) Å, α = 78.154(9)°, b = 73.742(9)° and γ = 82.751(8)°. In the complex, bix ligands acting as bridges link the Co(II) ions into a three-dimensional (3D) 6-connected anionic framework, and the nitrate ions, which not only act as charge balance ions but also act as template in the process of self-assembly, did not involve in coordinating to Co(II) ions.

Syntheses, structures, and properties of two- and three-dimensional coordination polymers based on bis(imidazole) and glutarate ligands

Two new coordination polymers, [Zn(bix)0.5(glu)]n (1) and {[Co(bix)(glu)]·4H2O}n (2), were synthesized (bix = 1,4-bis(2-methylimidazol-1-ylmethyl)benzene, glu = glutarate). In 1, each Zn(II) is connected by four glu ligands and extend to form a [Zn(glu)]n 2-D network. Adjacent [Zn(glu)]n 2-D networks are bridged by bix ligands to construct a 6-connected 3-D network based on the Zn2 unit. 2 shows an undulated 2-D (4,4) network. The interesting structural feature of 2 is that there are 1-D water chains. The O–H···O hydrogen bond interactions link the 2-D coordination networks and construct the 3-D supramolecular architecture in 2. The glu ligands are bis-(bidentate) bridges in 1 and bis-(monodentate) bridges in 2. The luminescence of 1 and thermal stability of 1 and 2 were investigated.

Crystal structure of poly[[{μ2-1,4-bis[(1H-imid-azol-1-yl)methyl]benzene}[μ6-5-(4-carboxylatophenoxy)isophthalato]-μ3-hydroxido-dicobalt(II)] 0.25-hydrate

The title coordination polymer, {[Co2(C15H7O7)(OH)(C14H14N4)]·0.25H2O}n, was synthesized under hydro­thermal conditions. The asymmetric unit contains two Co2+ ions, one L 3− anion originating from 5-(4-carb­oxy­phen­oxy)isophthalic acid (H3 L), one OH− ligand, one 1,4-bis­[(1H-imidazol-l-yl)meth­yl]benzene (bix) ligand and one disordered lattice water mol­ecule (occupancy 0.25). The two Co2+ ions have different environments. One has an octa­hedral O4N2 coordin­ation sphere, defined by four O atoms from three carboxyl­ate groups and one OH− ligand, and two N atoms from two symmetry-related bix ligands. The other has a trigonal-bipyramidal O5 coordination sphere resulting from three carboxyl­ate groups and two OH− ligands. The dihedral angles between the two benzene rings in the L 3− ligand and between the benzene ring and the two imidazole rings in the bix ligand are 67.05 (15), 75.27 (17) and 82.05 (17)°, respectively. Four neighbouring Co2+ ions are linked by six carboxyl­ate groups and two μ 3-OH ligands, forming a butterfly-shaped secondary building unit (SBU). These SBUs are connected by L 3− anions into layers parallel to (1-10). Adjacent layers are cross-linked by the bix ligands, forming a three-dimensional framework that has a bimodal (3,8)-connected tfz-d topology. The disordered lattice water mol­ecule is located in the voids of the framework and has O⋯O and O⋯N contacts of 2.81 (2) and 2.95 (2) Å, suggesting medium-strength hydrogen bonds. The title compound may be a good candidate for artificial eye lenses.

A New Two-Dimensional Mn(II) Coordination Polymer Based on Oxalic Acid and 1,4-Bis(imidazol-1-ylmethyl)-benzene

A new two-dimensional manganese coordination polymer has been prepared and fully characterized by single-crystal X-ray diffraction, elemental analyses, TG, and IR spectroscopy. Of the compound, the Mn(II) center is octahedral coordinated with oxate acting as a tetra-dentate ligand coordinated to the Mn(II) atom and each bix serving as a bridging ligand by employing two N-donor to coordinate with the Mn(II) center. An infinite {Mn2(C2O4)2}∞ chain is formed along the a axis. Furthermore, the 1D chains are held together via bix ligands to generate a two-dimensional network structure.

Hydrothermal Synthesis and Structure of a Zinc Complex Based on 5-Nitro-1,2,3-Benzenetricarboxylic Acid and 1,4-Bis(imidazol-1-ylmethyl)benzene

A new complex, [Zn3(nbta)2(bix)2.5·H2O]n (1) [H3nbta = 5-nitro-1,2,3-benzenetricarboxylic acid; bix = 1,4-bis(imidazol-1-ylmethyl)benzene], has been synthesized by hydrothermal reaction with Zn(II) acetate, H3nbta, and bix ligands. It was determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis and IR spectroscopy. The X-ray single-crystal structure shows that complex 1 belongs to the triclinic system, Pī space group, a = 9.919(6), b = 12.997(8), c = 22.679(13) Å, and α = 76.087(7), β = 81.429(8), γ = 81.429(8)°. Complex 1 exhibits a (3,4)-connected 3D network with a (4.6.8)2(62.8)(4.104.12)(4.62.82.10) topology, in which binuclear and mononuclear Zn(II) nodes are bridged by the nbta anions and bix ligands. The thermal stabilities of complex 1 have been briefly observed. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.

Poly[[(μ2-benzene-1,3-dicarboxylato){μ2-1,4-bis[(1H-imidazol-1-yl)methyl]benzene}cadmium] dimethylformamide monosolvate

The title coordination polymer, {[Cd(C8H4O4)(C14H14N4)]·C3H7NO}n, was synthesized by solvothermal reaction of metallic cadmium with the semi-rigid neutral ligand 1,4-bis­[(1H-imidazol-1-yl)meth­yl]benzene (bix) and the V-shaped benzene-1,3-di­carb­oxy­lic acid (m-H2bdc). The structure exhibits a pseudo-C-centring which is almost fulfilled by the polymeric metal complex but not by the solvent dimethylform­amide (DMF) mol­ecules. The asymmetric unit contains two independent CdII ions, two m-bdc2− ligands, one and two half bix ligands, and two solvent DMF mol­ecules. The CdII ions are both five-coordinated by three O atoms from two different m-bdc2− ligands and two N atoms from two different bix ligands in a distorted square-pyramidal geometry. The m-bdc2− ligands adopt a chelate-monodentate coordination mode, connecting neighboring CdII ions into a zigzag chain parallel to [110]. Adjacent chains are further cross-linked by bix ligands, giving rise to a puckered sheet nearly perpendicular to the chain direction. Thus, each CdII ion is connected to four neighboring CdII ions through two m-bdc2− anions and two bix ligands, giving rise to the final non-inter­penetrating uninodal layer with sql (4,4) topology.

Syntheses, structures, and photoluminescent properties of two silver (I) coordination polymers with 1, 4-bis(imidazol-1-ylmethyl) benzene

The ultrasonic reactions of Ag2O with 1, 4-bis(imidazol-1-ylmethyl) benzene (bix) and ancillary carboxylate ligands under the ammoniacal condition lead to two new coordination compounds, namely [Ag4(bix)4(pma)·(H2O)18]n(1) and [Ag(bix)(onb)·H2O]n(2)(H4pma =pyromellitic acid, Honb=o-nitrobenzoic acid). Both of the complexes have been characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. In complex 1, the Ag-bix 1D chains are connected with the 2D nets containing [Ag4(bix)2(pma)2] to form a 3D framework by Ag⋯Ag interaction. In complex 2, the coordination bonds link Ag(I) ions and bix ligands to form 1D chains which are extended into a 2D layer by inter-chain hydrogen bonds. The Ag⋯Ag interaction is also observed in 2. Moreover, the photoluminescence properties of the complexes were also investigated in the solid state at room temperature.

Syntheses and structural characterization of iron(II) coordination polymers with flexible 1,4-bis(imidazol-1-ylmethyl)benzene ligand

Iron(II) coordination polymers {[Fe(bix)2(NCS)2]·H2O}n (1) and [Fe(bix)2(N3)2]n (2) were synthesized using the flexible bidentate N-donor 1,4-bis(imidazol-1-ylmethyl)benzene (bix) ligand together with the mono-anionic ligands such as NCS− and N3− ions. In both of these complexes the iron(II) ion is in a distorted octahedral arrangement. Polymers 1 and 2, exhibit 2D framework with the ABCDE… and ABAB… packing modes, respectively. By considering the non-classical C–H⋯N hydrogen bonds, complex 2 is a three-dimensional polymer. Due to the presence of seven different kinds of trans-gauche conformations of the flexible bix ligands in the asymmetric unit of 1, there are four crystallographically independent iron(II) ions. In contrast to 1, in complex 2, all the bix ligands have the same conformation (trans-gauche). So, there is only one kind of iron(II) ion in this structure. Moreover, an attempted synthesis of [Fe(bix)3](ClO4)2 lead to the formation of unexpected diprotonated ionic species [bixH2](ClO4)2 (3) which was identified by X-ray analysis and infrared spectroscopy. Polymers 1 and 2 have been characterized by infrared spectroscopy, elemental and thermal analyses and single-crystal X-ray diffraction.

Hydrothermal Synthesis, Crystal Structure and Characterization of a Novel threefold Interpenetrating lvt Framework Based on a 104-Membered [Cd(Bix)] 8 16+ Ring

A novel threefold interpenetrating coordination framework {[Cd2(bix)4(SCN)4]} n (1) [bix = 1, 4-bis(imidazol-1-ylmethyl)benzene] was synthesized by hydrothermal reaction of Cd(OAc)2·2H2O, bix and NaSCN. The product was characterized by elemental analysis, IR spectra, TG, PXRD, and single-crystal X-ray diffraction. In 1, the bix ligand adopts a gauche-configuration to alternately link Cd(II) centers into a rare 104-membered ring with a chair-configuration containing eight repetitive [-Cd-bix-]2+ sub-uints. Through the shared Cd(II, the adjacent 104-membered rings are interconnected into a new 3D threefold interpenetrating 42 × 84-lvt framework. The thermal stability and photoluminescence property of 1 is also investigated. A novel 3D threefold interpenetrated lvt coordination framework{[Cd2(bix)4(SCN)4]} n , based on rare 104-membered ring [Cd(bix)] 8 16+ with chair-configuration, has been hydrothermally synthesized and characterized. Moreover, the thermal stability and photoluminescence property of 1 were also investigated.

Synthesis, crystal structure and magnetic characterization of two Mn(III) chains with Schiff-base ligands

Two new one-dimensional manganese(III) complexes [Mn2III(L1)4(piv)2] (1) and [MnIII(L2)(bix)]·2H2O⋅ClO4 (2) (H2L1=N-(2-hydroxyethyl)-3-methoxysalicylaldimine, H2L2=N,N′-bis(salicylidene)phenylenediamine, bix=1,4-bis-(imidazol-1-ylmethyl)benzene, piv=pivalate) have been synthesized and characterized by X-ray crystallography and magnetic measurements. Crystal structure studies reveal that complex 1 consists one-dimensional manganese(III) chains linked by L12- ligand in η1:η1:η1:μ2 mode. In complex 2, the Mn(III) ion is coordinated by the tetradentate L22- ligand in the equatorial plane, whereas bix ligand acts as bridge in the axial direction. Magnetic studies show that both complexes exhibit weak antiferromagnetic exchange coupling between Mn(III) ions.

N-donor ligand mediated assembly of divalent zinc and cadmium coordination polymers based on 2,3,2′,3′-thiaphthalic acid: structures and properties

A series of five metal–organic frameworks, namely, {[Cd2(tdpa)(H2O)3]·H2O}n (1), {[Cd2(tdpa)(bpe)(H2O)3]}n (2), {[Cd2(tdpa)(bix)]}n (3), {[Cd2(tdpa)(bpg)(H2O)4]·3H2O}n (4) and {[Zn4(tdpa)2(bpy)2(H2O)11]·4H2O}n (5) have been hydro(solvo)thermally synthesized through the reaction of 2,3,2′,3′- thiaphthalic acid (H4tdpa) with divalent zinc and cadmium salts in the presence of ancillary nitrogen ligands (bpy = 4,4′-bipyridine, bpg = meso-α,β-bi(4-pyridyl) glycol, bpe = 1,2-di(pyridin-4-yl)ethane and bix = 1,4-bis((1H-imidazol-1-yl)methyl)benzene) and structurally characterized by elemental analysis, IR and X-ray diffraction. In complexes 1, 2 and 3, rod-shaped {Cd12Cd22C6O10}n Cd-chain secondary building units (SBUs) have been formed. For 1, such rod-shaped SBUs are linked together through tdpa4− itself to form a metal–organic layer. For 2 and 3, such metal–organic SBUs are further associated together by bpe or bix ligands in four orientations to form a robust 3D metal–organic network, respectively. In compound 4, a 3D Cd–tdpa metal–organic network is accomplished through tdpa4− anion ligands, and further stabilized by bpg. In complex 5, zinc atoms are bridged by tdpa4− anion ligands and bpy to form infinite Zn–tdpa chains. Luminescence and thermal analysis of these complexes have also been investigated.

Temperature-induced assembly of MOF polymorphs: Syntheses, structures and physical properties

Four new coordination polymers, namely, [Co(BIPA)(titmb)]·H2O (1), [Co3(BIPA)3(titmb)2]·0.73H2O (2), [Ni(SDBA)(bix)]·2H2O (3) and [Ni(SDBA)(bix)(H2O)]·0.38H2O (4) (H2BIPA = 5-bromoisophthalic acid, H2SDBA = 4,4′-dicarboxybiphenyl sulfone, titmb = 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-tri-methylbenzene, bix = 1,4-bis(imidazol-1-ylmethyl)benzene), were obtained under hydrothermal conditions. Four complexes were characterized by elemental analyses, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction. Complexes 1 and 2 are polymorphs formed from Co(II) cations, BIPA2− anions, titmb ligands and water molecules, showing a three-dimensional (3,5)-connected network with the topology of (63)(69.8) for 1 and a three-dimensional (3,4)-connected coordination framework with the topology of (4.6.8)(4.62.83)(6.85)(62.83.10)(83) for 2. Complexes 3 and 4 are also two polymorphs constructed from Ni(II) cations, SDBA2− anions, bix ligands and water molecules. Complex 3 exhibits a two-dimensional lamella structure with (4,4) topology, whereas complex 4 displays a two-dimensional 2-fold interpenetrating (6,3) network. It is shown that the reaction temperature plays a crucial role in the formation of the final products. Moreover, the nonlinear optical and ferroelectric properties of 1 have also been investigated.

Factors Affecting the Conformational Modulation of Flexible Ligands in the Self-Assembly Process of Coordination Polymers: Synthesis, Structural Characterization, Magnetic Properties, and Theoretical Studies of [Co(pda)(bix)]n, [Ni(pda)(bix)(H2O)]n, [Cu(pda)(bix)2(H2O)2]n·8nH2O, [Co2(μ-OH)(pda)(ptz)]n·nH2O, [Co(hfipbb)(bix)0.5]n, and [Co(2,6-pydc)(bix)1.5]n·4nH2O

Six new metal complexes with the formulae [Co(pda)(bix)]n (1), [Ni(pda)(bix)(H2O)]n (2), [Cu(pda)(bix)2(H2O)2]n·8nH2O (3), [Co2(μ-OH)(pda)(ptz)]n·nH2O (4), [Co(hfipbb)(bix)0.5]n (5), and [Co(2,6-pydc)(bix)1.5]n·4nH2O (6) have been synthesized by the reactions of Co(II), Ni(II), and Cu(II) salts with two flexible ligands 1,4-phenylenediaceticacid (H2pda) and 1,4-bis (imidazole-1-ylmethyl)-benzene (bix) in the presence of coligands 5-(4-pyridyl) tetrazole (4-ptz), 4,4′(hexa-fluoroisopropylidene)bis(benzoicacid) (H2hfipbb), and 2,6-pyridine dicarboxylic acid (2,6-H2pydc) and characterized by single crystal X-ray diffraction analysis, IR spectroscopy, and thermogravimetric (TG) analysis. Because of the coordination geometry around the metal ions and the diverse coordination modes of the flexible ligands in combination with the rigid and flexible coligands, the obtained complexes show diverse structures from a one-dimensional (1D) chain to three-dimensional (3D) coordination polymers. 1, 4, 5, and 6 are Co(II) complexes in which Co(II) ions show tetrahedral coordination in 1, trigonal bipyrimidal coordination in 4, and octahedral coordination in 5 and 6. Complexes 2 and 3 are respectively Ni(II) and Cu(II) complexes in which the metal ions are present in octahedral coordination geometries. Factors affecting the conformational change of the flexible ligands in the self-assembly process of coordination polymers, such as, coordination geometry around the metal ions and geometry of the coligands have been systematically studied. The rotation of the bonds C(sp3)–C(sp2) and C(sp3)–N(sp3) in H2pda and bix ligands causes different conformations (cis, trans, gauche); these conformations have been studied by measuring the torsion angle. A comparative study between the torsion angle of the particular conformation of the ligands and coordination geometry of metal ion/geometry of the coligand has been undertaken. All the possible cis, trans, and gauche conformations of the flexible ligands have been obtained/observed in our complexes. Theoretical calculations were performed to determine the energies of the different conformations of the flexible ligands. The electronic properties of these complexes have also been investigated in the solid state at room temperature. Finally, the temperature-dependent magnetic studies for compounds 4 and 5 are described.