Five-, seven-, and eight-coordinate Cd(II) coordination polymers built by anthranilic acid derivatives: Synthesis, structures and photoluminescence

Two novel Cd(II) coordination polymers, [(CH₃)₂NH₂]₂[Cd(cma)₂](H₂O) (1) and [Cd₃(bcma)₂(H₂O)](H₂O) (2) (H₂cma = N-(carboxymethyl)-anthranilic acid, H₃bcma = N,N′-bis-(carboxymethyl)-anthranilic acid), have been synthesized under hydrothermal conditions and characterized by X-ray single crystal analysis, IR spectra and TGA. Compound 1 possesses 1D double-stranded chain, which further packs into square channels. Compound 2 consists of a novel 3D framework, which not only possesses unique meniscus-like channels but also contains infinite helical chains. Compound 2 is the first example of Cd(II)-aminopolycarboxylate coordination polymers containing three crystallographically independent Cd(II) centres, in which Cd(1), Cd(2), and Cd(3) present distorted pentagonal bipyramidal, tetragonal antiprismatic, and trigonal bipyramidal coordination geometry, respectively. Both compounds display intense room temperature photoluminescence in the solid state.     

Syntheses, structures and photoluminescence properties of cadmium(II) and zinc(II) complexes with pyridinylcarboxamide-containing ligand

Four new coordination complexes [Cd(DPBA-3)₂(H₂O)₂](ClO₄)₂·2H₂O (1), [Cd(DPBA-3)(DMF)(NO₃)₂]·DMF (2), [Cd₃(DPBA-3)₂(SCN)₆]·2DMF·4H₂O (3) and [Zn(DPBA-3)(SCN)₂] (4) [DPBA-3 = N,N′-di(pyridin-3-yl)pyridine-3,5-dicarboxamide] have been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction. Complexes 1, 3 and 4 exhibit three different types of one-dimensional (1D) chain structures constructed by the metal ions and DPBA-3 ligands, and the Cd(II)-DPBA-3 1D chains in 3 are further linked by bridging SCN⁻ ligands to afford a three-dimensional (3D) framework. Complex 2 possesses a (6,3) two-dimensional (2D) layer structure. In 1-4, the hydrogen bonds involving the amide groups play important role to stabilize the resultant frameworks. The photoluminescence properties of the DPBA-3 and the complexes were studied in the solid state at room temperature.     

Dinuclear oxovanadium(IV) compounds from designed amino acid derivatives

Two dinuclear oxovanadium(IV) compounds [V(O)(NMet)(μ-OMe)]₂ · MeOH (1) and [V(O)(NThr)(μ-OMe)]₂ · MeOH (2) were prepared by the reaction of VOSO₄ and ONN donor ligands, HNMet and HNThr (HNMet =N-(2-pyridylmethyl)-dl-methionine, HNThr = N-(2-pyridylmethyl)-dl-threonine) derived from 2-pyridinecarbaldehyde and dl-methionine/dl-threonine. Both of these compounds are characterized by single crystal X-ray diffraction. X-ray crystallography revealed that the two vanadium(IV) compounds are both dinuclear structures bridged by methanol groups. Each vanadium atom is six coordinated in a distorted octahedral environment. IR spectroscopy and EPR spectra for these two compounds are also given.     

Synthesis, crystal structures and properties of novel zinc(II) and cadmium(II) polymeric and cyclic bimetallic complexes with fluconazole and dicarboxylate co-ligands

Four new fluconazole-bridged zinc(II) and cadmium(II) complexes with dicarboxylate co-ligands, namely [Zn(HFlu)(TPA)]_n (1), {[Cd(HFlu)₂(TPA)]·2CH₃OH}_n (2), [Zn(HFlu)₂(Suc)(H₂O)₂]·H₂O (3), and [Cd(HFlu)₂(Suc)(H₂O)₂]·H₂O (4), have been synthesized and characterized by elemental analysis, IR, TG, and single-crystal X-ray diffraction (HFlu = 2-(2,4-difluorophenyl)-1,3-bis(1,2,4-triazol-1-yl)-propan-2-ol, H₂TPA = terephthalic acid, and H₂Suc = succinic acid). Complex 1 displays a 2-D corrugated network with common (4,4) topology, in which two types of grids constructed by two bridging TPA dianions and two HFlu ligands are found. Complex 2 shows an unusual (3,6) coordination layer consisting of alternative PMPM Cd-HFlu helical chains in which the Cd(II) nodes are also fixed by terephthalate dianions in a cis fashion. The isostructural complexes 3 and 4 have 20-membered dimeric macrocyclic motifs with the Zn···Zn and Cd···Cd distances of 11.258(2) and 11.528(2) Å, respectively. The fluorescence and thermal stability of complexes 1-4 have also been investigated.     

Cadmium(II) and zinc(II) coordination polymers with mixed building blocks of benzenedicarboxyl and 2,5-bipyridyl-1,3,4-oxadiazole: Syntheses, crystal structures, and properties

Three Cd(II) and Zn(II) coordination polymers, including {[Cd(3-bpo)(mip)(H₂O)](H₂O)₂}_n (1), {[Cd(4-bpo)(hip)(H₂O)](H₂O)₄}_n (2), and {[Zn(4-bpo)(tp)](CH₃OH)}_n (3) were synthesized from the reactions of Cd^II or Zn^II nitrate with mixed organic ligands [3-bpo = 2,5-bis(3-pyridyl)-1,3,4-oxadiazole, H₂mip = 5-methylisophthalic acid, 4-bpo = 2,5-bis(4-pyridyl)-1,3,4-oxadiazole, H₂hip = 5-hydroxylisophthalic acid, H₂tp = terephthalic acid] under the similar layered diffusion condition. The resulting crystalline materials 1-3 were characterized by IR, microanalysis, powder X-ray diffraction (PXRD) techniques. Single-crystal X-ray diffraction indicates a 1-D tubular motif for 1, a 1-D dual-track array for 2, and a 2-D grid-like pattern for 3, constructed via different metal-ligand coordination contacts. Higher-dimensional supramolecular architectures are further assembled in 1-3 via H-bonding and aromatic stacking interactions. In addition, thermal stability and fluorescence of these polymeric complexes were also investigated and discussed.     

Molecular interactions of zinc(II) cyclams with polycarboxylato ligands

Four new zinc(II) cyclams of the composition {Zn(L)(tp²⁻) · H₂O}_n (1), {Zn(L)(H₂bta²⁻) · 2H₂O}_n (2), [Zn₂(L)₂(ox²⁻)] 2ClO₄ · 2DMF (3), and Zn(L)(H₂btc⁻)₂ · 2DMF (4), where L = cyclam, tp²⁻ = 1,4-benzenedicarboxylate ion, H₂bta²⁻ = 1,2,4,5-benzenetetracarboxylate ion, ox²⁻ = oxalate ion, DMF = N,N-dimethylformamide, and H₂btc⁻ = 1,3,5-benzenetricarboxylate ion, have been synthesized and structurally characterized by a combination of analytical, spectroscopic and crystallographic methods. The carboxylato ligands in the complexes 1-4 show strong coordination tendencies toward zinc(II) cyclams with hydrogen bonding interactions between the pre-organized N-H groups of the macrocycle and oxygen atoms of the carboxylato ligands. The macrocycles in 1, 2, and 4 adopt trans-III configurations with the appropriate R,R,S,S arrangement of the four chiral nitrogen centers, respectively. However, the complex 3 shows an unusual cis V conformation with the R,R,R,R nitrogen configuration. The finding of strong interactions between the carboxylato ligands and the zinc(II) ions may provide additional knowledge for the improved design of receptor-targeted zinc(II) cyclams in anti-HIV agents.     

Hydrothermal synthesis, crystal structures and photoluminescent properties of four cadmium(II) coordination polymers derived from diphenic acid and auxiliary ligands

Four novel metal coordination polymers, [Cd(dpa)(H₂O)]_n (1), [Cd(dpa)(2,2′-bipy)]_n (2), {[Cd₂(dpa)₂(4,4′-bipy)₃](4,4′-bipy)(H₂O)₂}_n (3) and [Cd(dpa)(bim)₂(H₂O)]}_n (4) (H₂dpa = 2,4′-biphenyl-dicarboxylic acid, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, bim = benzimidazole), have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses reveal that the 2,4′-diphenic acids acts as bridging ligands, exhibiting rich coordination modes to link metal ions: bis-monodentate, bidentate chelating, chelating/bridging, monoatomic bridging and monodentate modes. In addition, the luminescent properties for compound 1-4 are also investigated in this work.     

Synthesis, structure and biological activities of cobalt(II) and zinc(II) coordination compounds with 2-benzimidazole derivatives

In this work we present the synthesis, structural and spectroscopic characterisation of a series of cobalt(II) and zinc(II) coordination compounds with benzimidazole (bz) and its 2-benzimidazole derivatives: 2-aminobenzimidazole (2ab), albendazole (abz) and tris(2-benzimidazolylmethyl)amine (ntb). The compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Micrococcus luteus, Salmonella typhi, Pseudomonas aeruginosa, Escherichia coli and Proteus vulgaris. Their cytotoxic activity was also evaluated using human cancer lines, HeLa, HCT-15 and SKLU-1. The halide tetrahedral compounds [Co(bz)₂Br₂] 3, [Zn(2ab)₂Cl₂] · 0.5H₂O 11, [Co(abz)Cl₂(H₂O)] · 3H₂O 14, [Co(abz)Br₂(H₂O)] 15, [Zn(abz)Cl₂(H₂O)] · 3H₂O 17 and [Zn(abz)Br₂(H₂O)] · H₂O 18 displayed similar minimal inhibition concentration (MIC) values against Micrococcus luteus and Escherichia coli, comparable to those of amoxicillin and chloramphenicol. Additionally, 11 showed a wide range of activity towards Gram(+) and Gram(−) microorganisms. The tetradentate ntb and its trigonal bipyramidal cobalt(II) and zinc(II) compounds were active, regardless of the anion present in the complex. Compound [Co(abz)Cl₂(H₂O)] · 3H₂O 14 showed promising activity in HeLa cells, while [Co(ntb)Br]Br · H₂O 21 inhibited Hela and HCT-15 cell lines.     

Crystal structures and luminescent properties of zinc(II) and cadmium(II) compounds constructed from 5-sulfoisophthalic acid and flexible bis-triazole ligands

Four new cadmium(II) and zinc(II) coordination polymers {[Zn(btrp)(SIP)][Zn_0.5(H₂O)₃]}_n (1), {[Cd_1.5(btrp)(SIP)(H₂O)₂]·2H₂O}_n (2), {[Cd_1.5(btrb)(SIP)(H₂O)₃]·2H₂O}_n (3), {[Zn_1.5(btrb)_1.5(SIP)(H₂O)₂]·2H₂O}_n (4) (btrp = 1,3-bis(1,2,4-triazol-1-yl)propane, btrb = 1,3-bis(1,2,4-triazol-1-yl)butane, NaH₂SIP = 5-sulfoisophthalic acid monosodium salt) have been synthesized under hydrothermal conditions and structurally characterized. Compound 1 possesses an infinite 1D ladder-like chain structure with [Zn(H₂O)₆]²⁺ trapped in the pores, which is further interconnected by π?π interactions to lead to a 2D supramolecular architecture. Compounds 2 and 3 features two similar 2D layer structures, and the resulting 2D structures are interconnected by hydrogen-bond interactions to lead to 3D supramolecular architectures. Compound 4 is a 2D parallel ladder structure, and through the interpenetrating btrb ligand, it constructs into 3D architectures. Luminescence analyses were performed on all the four compounds, which show strong fluorescent emissions in the solid state at room temperature.     

Novel Zn (II) and Pb (II) coordination networks with large circuits: Synthesis, crystal structures and self-focusing effects

Two coordination polymers {[Zn(btx)₂(NO₃)₂]}_n (1) and {[Pb(btx)_1.5(NCS)]NO₃}_n (2) (btx = 1,4-bis(triazol-1-ylmethyl)benzene) have been synthesized and characterized by X-ray diffraction. Polymer 1 exhibits a 2-D network with square grid units and polymer 2 possesses an unusual 2-D layered structure with 78-membered rings. By studying the third-order nonlinear optical properties of ligand btx, polymers 1 and 2, we find that they all show strong self-focusing effects. A reasonably good fit between the experimental data and the theoretical curves suggests that the experimentally obtained NLO effects are effectively third-order in nature. The refractive index n₂ values are 4.50 × 10⁻¹⁸ m² W⁻¹ for btx, 3.09 × 10⁻¹⁸ m² W⁻¹ for 1, and 6.01 × 10⁻¹⁸ m² W⁻¹ for 2. All these data can match those of the best-known third-order NLO materials such as inorganic oxides, semiconductors, and cluster compounds. In addition, we discuss the influence of the ligand and central metals on the third-order NLO properties of coordination polymers.     

Hydrothermal synthesis and characterization of a two-dimensional nickel(II) complex containing benzenehexacarboxylic acid (mellitic acid)

The hydrothermal synthesis, single crystal X-ray structure and magnetic properties of a two-dimensional (2-D) coordination polymer, [Ni₄(C₆(COO)₆)(OH)₂(H₂O)₆] (1), is described. Complex 1 consists of dimer motifs of pseudo octahedral NiO₆ linked through μ3-OH to generate one-dimensional (1-D) chains which are further bridged by the mellitate ligands to form non interpenetrated undulating sheet structure. The sheets are further connected by hydrogen bonding interaction to yield a three-dimensional (3-D) structure. The temperature dependence of magnetic susceptibilities revealed the presence of antiferromagnetic interaction between nickel centers.     

One-dimensional Zn(II) oligo(phenyleneethynylene)dicarboxylate coordination polymers: Synthesis, crystal structures, thermal and photoluminescent properties

The rigid, π-conjugated dicarboxylic acid 1,4-bis-[2-(4-carboxyphenyl)ethynyl]-2,5-dihexylbenzene {HO₂C[PEP(hexyl)₂EP]CO₂H} has been used to synthesise the new crystalline coordination polymers {Zn(O₂C[PEP(hexyl)₂EP]CO₂)(DMF)₂} (1) and {Zn(O₂C[PEP(hexyl)₂EP]CO₂)(DEF)₂} (2) in N,N-dimethylformamide (DMF) and N,N-diethylformamide (DEF), respectively, under mild conditions. Single-crystal X-ray crystallography revealed that 1 and 2 are isostructural and consist of uncharged zigzag coordination chains in which [Zn(formamide)₂]²⁺ fragments are bridged by (O₂C[PEP(hexyl)₂EP]CO₂)²⁻ ligands. The zigzag chains possess different intra-chain Zn?Zn?Zn angles due to the different volumes of the coordinating formamide molecules and subtle differences in the hydrophobic inter-chain interactions. Upon heating 1 and 2 to 200 °C, removal of the coordinating formamide molecules occurs, yielding the formamide-free compounds 1-DMF and 2-DEF of composition {Zn(O₂C[PEP(hexyl)₂EP]CO₂)}. According to powder X-ray diffraction and FT-IR spectroscopy studies, these materials are not crystalline but still possess partial ordering of intact, yet modified coordination chains in a structural arrangement which appears to be related to the respective parent compounds. Compounds 1, 2, 1-DMF and 2-DEF exhibit blue photoluminescence. The emission maxima of 1-DMF and 2-DEF are red-shifted by ca. 25 nm with respect to λ_max of 1 and 2, respectively.     

Four novel Co(II) and Mn(II) coordination polymers with triazolyl derivate: Syntheses, crystal structures and magnetic properties

Four novel coordination polymers, one-dimensional chains [M(PTE)₂(N₃)₂]_n (M = Mn for 1 and Co for 2), and two-dimensional layers [M(PTE)₂(dca)₂]_n (M = Mn for 3 and Co for 4) (PTE = 1-(2,4-difluorophenyl-2-(1H-1,2,4-triazol-1-yl)ethanone, dca = dicyanamide anion, N(CN)₂⁻), have been synthesized under mild ambient conditions and structurally characterized by single crystal X-ray diffraction. In all four crystal structures, the metal atoms adopt octahedral coordination geometry with six nitrogen atoms from two monodentate PTE ligands and four azido (or dca) bridging ligands. The crystal structures of 1 and 2 are isostructural 1-D polymeric chains, alternatively linked by double end-on and double end-to-end azido bridges. However, the bent dca ligands as bidentate μ₂-1,5 bridging ligands interlink the octahedral metal units to lead to 2-D (4,4) grid networks in 3 and 4. Temperature-dependent magnetic measurements in 2-300 K have been performed for these four polymers, and suggest alternative ferro- and antiferromagnetic couplings for end-on and end-to-end azido bridges in 1, and the dominant ferromagnetic coupling in 2, respectively. Both polymers 3 and 4 show weak antiferromagnetic exchanges through the μ₂-1,5-dca bridges. The effects of auxiliary coligands on the structure and the nature of these magnetic exchanges are discussed in the light of the crystal structures in detail.     

Bimetallic copper(II) and zinc(II) complexes of acyclic Schiff base ligands derived from amino acids

The acyclic Schiff-base ligands (2-(OH)-5-(R³)C₆H₂-1,3-(HCNC(R¹)(R²)CO₂H), derived from the dialdehyde 2-hydroxy-5-R-1,3-benzenedicarboxaldehyde (R = Me or t-Bu) and two equivalents of the amino acids glycine, 2,2-diphenylglycine or phenylalanine, have been reacted with the metal acetates M(OAc)₂ (M = Cu, Zn) in the presence of triethylamine, affording the complexes [HNEt₃][M₂(CH₃CO₂)₂(2-(O)-5-(t-Bu)C₆H₂-1,3-(HCNC(R¹)(R²)CO₂)₂] (M = Cu, R¹ = R² = C₆H₅, R³ = Me (1); M = Zn, R¹ = R² = H, R³ = t-Bu (2); M = Zn, R¹ = R² = C₆H₅, R³ = t-Bu (3); M = Zn, R¹ = H, R² = CH₂C₆H₅, R³ = t-Bu (4)) in good yields. The crystal structures of 1·MeCN, 2·, 3·2MeOH, and 4·3MeOH have been determined.     

Two-dimensional coordination polymers of Zn(II) and Cd(II) derived from 3,3′,5,5′-azobenzenetetracarboxylic acid exhibiting solvent facilitated structure reversibility

Two Cd(II) and Zn(II) coordination polymers based on 3,3′,5,5′-azobenzenetetracarboxylic acid (H₄abtc): [Cd₂(abtc)(H₂O)₆]·DMF·0.5H₂O (1) and [Zn₂(abtc)(bpy)(H₂O)₂]·DMF·H₂O (2) are synthesized and structurally characterized. Both 1 and 2 are 2D polymers but interconnected by solvent molecules to generate 3D suprastructures. Solvent expulsion leads to rupture of both structures, but upon re-exposure to the solvent mixture they exhibit remarkable ability to regain the original structure reversibly from the almost amorphous solvent-expelled form. Compounds with such structural flexibility and reversibility are expected to have some useful functionality.     

Structure and luminescence of sodium and lanthanide(III) coordination polymers with pyridine-2,6-dicarboxylic acid

A series of coordination polymers constructed by sodium, lanthanide(III), and pyridine-2,6-dicarboxylate (dipic),NaLn(dipic)₂ · 7H₂O (Ln = Eu, Gd, Tb), have been prepared under a hydrothermal condition. The crystal structures of the three compounds which are isostructual were determined by single-crystal X-ray diffraction. The two-dimensional layers found in the compounds are built up from six-folded {NaO₆} polyhedra and nine-folded {LnN₂O₇} polyhedra, these being edge-shared each other along the c axis and bridged by carboxylate groups of dipic along the b axis, respectively. This two-dimensional framework provides cavities inside the layer and interlayer spaces outside the layer for accommodation of the two dipic molecules coordinated to a lanthanide(III) ions. The dehydrated materials obtained by heating the as-synthesized crystals at 200 °C held their crystal structure, and absorbed the same amounts of water molecules as those of the as-synthesized crystals upon the exposure of 100% relative humidity at room temperature. The Eu and Tb compounds showed strong red and green emissions, respectively, due to an energy transfer from dipic molecules to trivalent emission ions.     

Nickel(II)-, cobalt(II)-, copper(II)-, and zinc(II)-phthalate and 1-methylimidazole coordination compounds: synthesis, crystal structures and magnetic properties

Three new coordination polymers [M(Pht)(1-MeIm)₂]_n (where M=Cu (1), Zn (2), Co (3); Pht²⁻=dianion of o-phthalic acid; 1-MeIm=1-methylimidazole) and two compounds [M(1-MeIm)₆](HPht)₂ · 2H₂O (M=Co (4), Ni (5)) have been synthesized and characterized by X-ray crystallography. The structures of 1-3 (2 is isostructural to 3) consist of [M(1-MeIm)₂] building units connected by 1,6-bridging phthalate ions to form infinite chains. In complex 1, each copper(II) center adopts a square coordination mode of N₂O₂ type by two O atoms from different phthalate ions and two N atoms of 1-MeIm, whereas in 3 two independent metal atoms are tetrahedrally (N₂O₂) coordinated to a pair of Pht ligands and a pair of 1-MeIm molecules. There are only van der Waals interactions between the chains in 1, while the three-dimensional network in 3 is assembled by C-H?O contacts. In contrast to polymers 1-3 the structures of 4 and 5 (complexes are also isostructural) are made up of the [M(1-MeIm)₆]²⁺ cation, two hydrogen phthalate anions (HPht⁻) and two H₂O solvate molecules. The coordination around each metal(II) atom is octahedral with six nitrogen atoms of 1-MeIm. Extended hydrogen bonding networks embracing the solvate water molecules and a phthalate residue as well as the weak C-H?O interactions stabilize the three-dimensional structures. Magnetic studies clearly show that the magnetic ions do not interact with each other. Furthermore, in compound 4 we have another example of a highly anisotropic Co²⁺ ion with a rhombic g-tensor and large zero-field-splitting. The complexes were also characterized by IR and ¹H NMR spectroscopy, thermogravimetric analysis, and all data are discussed in the terms of known structures.     

Sonochemical syntheses of strawberry-like nano-structure mixed-ligand lead(II) coordination polymer: Thermal, structural and X-ray powder diffraction studies

Nano-structure of a new Pb(II) two-dimensional coordination polymer, {[Pb(2-pyc)(N₃)(H₂O)]_n (1), 2-Hpyc = 2-pyridinecarboxylic acid} was synthesized by a sonochemical method. The new nano-structure was characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. Compound 1 was structurally characterized by single crystal X-ray diffraction and consists of two-dimensional polymeric units. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses and compared. PbO nano-powder was obtained by calcination of the nano-structure of compound 1 at 400 °C. This study demonstrates the coordination polymers may be suitable precursors for the preparation of nano-scale materials and dependent on their packing they may produce different and interesting morphologies.     

Four copper(II) coordination polymers with a tetrachlorinated benzenedicarboxylate ligand: Solvent effect on diversiform supramolecular arrays

To further investigate the solvent effect on the structures of coordination polymers, a series of polymeric Cu^II complexes have been synthesized and characterized by single-crystal diffraction through combining of 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid (H₂BDC-Cl₄) with Cu^II perchlorate. The products including {[Cu(BDC-Cl₄)(py)₃] · H₂O}_n (py = pyridine) (1), {[Cu(BDC-Cl₄)(dioxane)(H₂O)₂] · dioxane}_n (2), and {[Cu₂(BDC-Cl₄)₂(DMF)₄] · 2G}_n (G = MeOH in 3 and G = EtOH in 4) have been obtained in different mixed solvents systems. With the change of the solvent system from pyridine/H₂O (1:1) into dioxane/H₂O (1:1), the infinite 1-D Cu^II-BDC-Cl₄ chain motif in 1 is tuned into the 2-D (4,4) layered structure in 2 with the coordination of dioxanes to copper atoms. When the solvent system is changed into DMF/MeOH (1:1), then into DMF/EtOH (1:1), similar 1-D Cu^II-BDC-Cl₄ double chains are afforded in 3 and 4 with different solvents inclusion. Moreover, the judicious choice of binding-guests leads to numerous coordination geometries of Cu^II centers and final dissimilar supramolecular lattices of 1-4 from 1-D to 3-D via robust hydrogen-bonding interactions. The spectroscopic, thermal, and fluorescent properties of 1-4 have also been investigated.     

Anion-directed supramolecular assembly of cobalt(II)-fluconazole coordination polymers: Structural diversity, fluorescent and magnetic properties

Six fluconazole-bridged cobalt(II) coordination polymers, namely [Co(HFlu)₂(H₂O)₂](ClO₄)₂ (1), [Co(HFlu)₂(H₂O)(AcO)](AcO)·2C₂H₅OH (2), [Co(HFlu)₂Cl₂]·2C₂H₅OH (3), [Co₃(Flu)₂(acac)₄]·C₂H₅OH (4), [Co(HFlu)₂(malo)(H₂O)]·3H₂O (5), and [Co(HFlu)₂(fum)(H₂O)₂]·H₂O (6) (HFlu = 2-(2′,4′-difluorophenyl)-1,3-bis(1,2,4-triazol-1-yl)-propan-2-ol, AcOH = acetate acid, Hacac = acetylacetonate, H₂malo = malonate acid, H₂fum = fumaric acid), have been synthesized and structurally characterized, and the thermal, fluorescent and magnetic properties investigated. The crystal structures display the one-dimensional cationic double-bridged chain consisting of 20-membered macrocycles to be parallel in 1 and perpendicular in 2. The structure of 3 consists of two-dimensional neutral rhombic grid in bc plane with (4,4) topology and alternative P/M helices intersecting at the Co sites along b direction. Complex 4 shows one-dimensional polymeric chain, in which binuclear Co₂(Flu)₂(acac)₂ units act as bridging blocks to link Co(acac)₂ nodes through triazolyl nitrogen atoms. The structure of 5 shows dimeric 20-membered macrometallacyclic motif. Complex 6 shows HFlu-bridged one-dimensional chain, which is stabilized by hydrogen-bonding interactions to produce alternative hydrophobic and hydrophilic architecture. Complexes 1-3 and 5-6 exhibit the similar electronic absorption and fluorescent spectra as those of HFlu, while complex 4 shows a fluorescent quenching phenomenon. Fluorescence titration of HFlu suggests that the fluorescent intensities at the maximal emission decrease upon the addition of Co(acac)₂. The variable-temperature magnetic measurement of 4 reveals weak ferromagnetic interaction combined with the spin-orbit coupling effect in the 1-D Co(II) chain.