3D supramolecular network assembly and thermal decomposition of new copper(II) complexes with pyrazine-2,6-dicarboxylic acid

Four new Cu(II) complexes [Cu(pzda)(2,2′-bpy)(H₂O)] · 2.5H₂O (1), [Cu(pzda)(phen)(H₂O)] · H₂O (2), [Cu(pzda)(4,4′-bpy)] · H₂O (3) and [Cu(pzda)(bpe)_0.5(H₂O)] (4) were synthesized by hydrothermal reactions of copper salt (acetate or sulphate) with pyrazine-2,6-dicarboxylic acid (H₂pzda), and 2,2′-bipyridine (2,2′-bpy), 1,10-phenanthroline (phen), 4,4′-bipyridine (4,4′-bpy) or 1,2-bis(4-pyridyl)-ethane (bpe), respectively. For 1 and 2, they are both monomeric entities which are further assembled into 3D supramolecular networks by hydrogen bonds and π-π stacking interactions. Complex 3 has a 2D metal-organic framework which is connected into 3D supramolecular network by hydrogen bonds. However, for 4, the bpe ligand bridges two Cu(II) ions into binuclear unit, and then the binuclear molecules are assembled into 3D supramolecular network by hydrogen bonds between the coordination water molecule and the carboxylate oxygen atoms. The thermal decomposition mechanism of complexes 1 and 2 cooperated with powder XRD at different temperatures is discussed. The results reveal that once liberation of water molecules takes place the supramolecular network of 1 and 2 collapses.     

Synthesis, spectral characterization, and single crystal X-ray structures of a series of manganese-2,2′-bipyridine complexes derived from substituted aromatic carboxylic acids

Reaction of [Mn(2,2′-bpy)₂(OAc)](ClO₄)(H₂O) with a series of aromatic carboxylic acids yields new Mn(II)carboxylates [Mn(2,2′-bpy)₂(L)](ClO₄)}₂ (1-3), [Mn(2,2′-bpy)₂(L)₂] (4-5) and [Mn(2,2′-bpy)₂(L)(H₂O)](ClO₄) (6) (L = 2-aminobenzoate (2-aba) (1), 4-hydroxybenzoate (4-hba) (2), thiophene-2-carboxylate (2-tca) (3), 2-hydroxynapthoate (2-hnapa) (4), 3,5-diisopropylsalicylic acid (dipsa) (5), 2,4,6-triisopropylbenzoate (tipba) (6)). The new compounds have been characterized with the aid of elemental analysis, spectroscopy, and single-crystal X-ray diffraction studies. Compounds 1-3, which have been synthesized from less bulky carboxylic acids, are dimeric in the solid-state. Compounds 4-6, which are derived from more bulkier aromaric carboxylic acids, exist as monomeric complexes. In the case of 6, where very bulky 2,4,6-triisopropyl benzoic acid is used as the starting material, only one carboxylate ligand binds to the metal, resulting in a cationic complex. Interestingly in all the six complexes, the C-H hydrogen atoms of the 2,2′-bpy ligands are involved in extensive hydrogen bonding with the carboxylate oxygen atoms of the adjacent molecules and hence form non-covalent 1-D or 2-D aggregates in the solid state.     

Synthesis, crystal structures, and characterization of three coordination compounds constructed from 4-sulfophthalic acid ligand

Three new coordination compounds with 4-sulfophthalic acid (H₃SPA) ligand, namely {[Pb₃(4-SPA)₂(H₂O)](H₂O)}_n (1), [Mn(4,4′-bpy)₂(H₂O)₄][Mn₂(4-SPA)₂-(4,4′-bpy)₄(H₂O)₄]·7.5(H₂O) (2) and Cu₂(4-HSPA)₂(2,2′-bpy)₂(H₂O)₂ (3) (4,4′-bpy = 4,4′-bipyridine and 2,2′-bpy = 2,2′-bipyridine), have been synthesized. The structures exhibit different dimensionality depending on the nature of the metal ions and/or the ancillary ligands. Compound 1 has a 2D layered architecture constructed from one-dimensional inorganic lead(II) oxygen chains containing tetranuclear [Pb₄(μ₂-O)₄] cluster. Compound 2 has a dinuclear manganese [Mn₂(4-SPA)₂(4,4′-bpy)₄(H₂O)₄] motif charged with mononuclear [Mn(4,4′-bpy)₂(H₂O)₄]²⁺ cation. Compound 3 is a discrete dinuclear copper(II) structure that linked by extensive hydrogen bonds to form a three-dimensional supramolecular structure. In the solid state, compound 1 exhibits blue photoluminescence with the maximum at 432 nm upon excitation at 350 nm. The temperature-dependent magnetic susceptibility data of 2 have been investigated. The Curie constant C and Weiss constant θ are 3.14 emu K mol⁻¹ and −2.09 K, respectively, revealing antiferromagnetically magnetic interactions between the Mn²⁺ ions. In addition, these compounds are characterized by powder X-ray diffraction, IR, elemental analysis, and thermogravimetric analysis.     

Cd(II) coordination polymers constructed from flexible disulfide ligand: Solvothermal syntheses, structures and luminescent properties

Four novel coordination polymers, [Cd(Hdtbb)(dtbb)_0.5(DMF)]_n (1), {[Cd(dtbb)(2,2′-bpy)(H₂O)]·2DMA}_n (2), {[Cd₂(dtbb)₂(1,4-bix)₂]·3DMF}_n (3) and [Cd(dtbb)(1,4-btx)]_n (4) [H₂dtbb = 2,2-dithiobisbenzoic acid, 2,2′-bpy = 2,2′-bipyridine, 1,4-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, 1,4-btx = 1,4-bis(triazol-1-ylmethyl)benzene] have been synthesized and structurally characterized. Complexes 1 and 2 possess one-dimensional (1D) infinite structures. The structures of complexes 3 and 4 exhibit two dimensional (2D) frameworks, which mainly due to the differences in the bridging modes of dtbb²⁻ ligand and the effect of the N-donor auxiliary ligands. The infrared spectra, thermogravimetric and luminescent properties were also investigated for these compounds.     

Studies of mononuclear and dinuclear complexes of dibromodimethylplatinum(IV): Preparation, characterization and crystal structures

A number of complexes of the types [PtBr₂Me₂(N^?N)] (N^?N = 4,4′-di-Me-2,2′-bpy (1); 4,4′-di-t-Bu-2,2′-bpy (2); 2,2′-bpz (3); bpym (4)) and [PtBr₂Me₂(L)₂] (L = H-pz (5); 4-Me-H-pz (6); H-idz (7); H-im (8); H-bim (9); quaz (10)) are reported. Characterization by NMR (¹H, ¹³C and ¹⁹⁵Pt), IR and EI-MS is given. In addition, crystal structures of several of these complexes are described. Furthermore, interactions within these structures including intramolecular hydrogen bonding and π-π stacking interactions are reported. The reactivity of selected mononuclear complexes was investigated and yielded two dinuclear complexes [PPh₄][(PtBrMe₂)₂(μ-Br)(μ-pz)₂] (11) and [(PtBr₂Me₂)₂(μ-bpym)] (12), respectively. The latter complex is accompanied by a solid-state structure. Finally, the thermal stability of all complexes is reported.     

Coordination compounds of tetrazolate-5-carboxylate with cobalt(II): Synthesis, structure and magnetic properties

Four coordination compounds of tetrazolate-5-carboxylate (tzc) with cobalt(II), [Co₂(tzc)₂(H₂O)₆]·2H₂O (1), [Co₂(tzc)₂(phen)₂(H₂O)₂]·2H₂O (2), [Co₂(tzc)₂(2,2′-bpy)₂(H₂O)₂]·H₂O (3), and [Co(tzc)(4,4′-bpy)] (4), where phen = 1,10-phenanthroline, 2,2′-bpy = 2,2′-bipyridyl, and 4,4′-bpy = 4,4′-bipyridyl, have been synthesized by the hydrothermal methods involving the in situ generation of the ligand from sodium ethyl tetrazolate-5-carboxylate. Compounds 1, 2 and 3 all contain dinuclear molecules in which metal ions are linked by the double N-N bridges from two tzc ligands in the μ₂-N₁,O₁:N₂ mode, and the dinuclear molecules are associated into 3D architecture through extensive hydrogen bonding and π-π stacking interactions in various fashions. Compound 4 exhibits a two-dimensional layer structure in which Co(tzc) chains with μ₃-N₁,O₁:O₁:N₂ tzc are cross-linked by 4,4′-bpy. Magnetic investigations on 1-3 revealed intramolecular ferromagnetic coupling through the double N-N bridges with intermolecular ferromagnetic or antiferromagnetic interactions. The interaction through the mixed N-N and μ₂-O_carboxylate bridges in 4 is antiferromagnetic.     

Syntheses and characterization of two metal-water clusters

Complexes 1 and 2, formulated {[Co₂(4,4′-bpy)₂ · 8H₂O] · (CCA)₂ · 4H₂O}_n (1) and {[Co(TMG)(4,4′-bpy)(H₂O)₂] · 3H₂O}_n (2) (H₂CCA = 2-carboxylatocinnamate, H₂TMG = 3,3-tetramethyleneglutate, 4,4′-bpy = 4,4′-bpyridine) have been synthesized by the reaction of cobalt (II), 4,4′-bpy and carboxylate ligands, in which 2D metal-water layers and 1D metal-water chains have been observed, respectively. In the metal-water clusters, the water molecules are trapped by the cooperative association of coordination interactions as well as hydrogen bonds.     

Hybrid organic-inorganic assemblies built up from saturated heteropolyoxoanions and copper coordination polymers with mixed 4,4′-bipyridine and 2,2′-bipyridine ligands

Three new organic-inorganic hybrid compounds [Cu^I(2,2′-bipy)(4,4′-bipy)_0.5]₂[Cu^I(2,2′-bipy)(4,4′-Hbipy)][Cu^I(4,4′-bipy)]₂[P₂W₁₈O₆₂] · 3H₂O (1), [Cu^I(2,2′-bipy)(4,4′-bipy)_0.5]₂[Cu^I(4,4′-bipy)]₂[PW₁₂O₄₀] · 0.25H₂O (2), and[Cu^I(4,4′-bipy)]₃[PMo₁₂O₄₀] · en · 3H₂O (3) (2,2′- bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine), have been hydrothermally synthesized. Compound 1 represents the first 1D ladderlike structure formed by Dawson-type polyoxoanion [P₂W₁₈O₆₂]⁶⁻ and coordination polymer with mixed 4,4′-bipy and 2,2′-bipy ligands. The novel structure of 2 is composed of 1D hybrid zigzag chains linked by chains into a 3D framework. In compound 3, the [PMo₁₂O₄₀]³⁻ clusters are hung on chains to form a new 1D chain.     

Manganese(II) coordination polymers with bis(5-tetrazolyl)methane: Synthesis, structure and magnetic properties

Two new Mn(II) coordination polymers with bis(5-tetrazolyl)methane (H₂btm), [Mn(btm)(phen)(H₂O)] · H₂O (1) and [Mn(btm)(2,2′-bpy)] · 1.5H₂O (2), have been synthesized and their structures determined by X-ray diffraction. In complex 1, the btm ligands assume the μ₂-1,1′:4 coordination mode and interlink Mn(II) ions into infinite one-dimensional chains. The chains are assembled into a three-dimensional architecture via hydrogen bonds and π-π interactions. For 2, Mn(II) ions are connected by btm ligands in the μ₃-1,1′:2:3′ mode to produce two-dimensional (6,3) coordination network. Magnetic investigations revealed that interactions through the btm bridges in both 1 and 2 are antiferromagnetic.     

A comparative study of ferrocenyl carboxylate cadmium(II) complexes prepared by two different synthetic methods

Reaction of ferrocenyl carboxylate H₂bfcs with Cd(Ac)₂ · 2H₂O (H₂bfcs = 1,1′-bis(3-carboxy-1-oxopropyl)ferrocene) gives the mononuclear tetrahydrate precursor Cd(Hbfcs)₂(H₂O)₄ (1). Investigation on the substitution reactions of 1 with imidazole or 2,2′-bpy afforded two one-dimensional (1D) complexes {[Cd₂(bfcs)₂(C₃H₄N₂)₆] · 4H₂O}_n (2) and {[Cd(bfcs)(2,2′-bpy)(H₂O)] · 2H₂O}_n (4) (2,2′-bpy = 2,2′-bipyridine), respectively. However, the one-step reactions of H₂bfcs, Cd(Ac)₂ · 2H₂O with imidazole or 2,2′-bpy result in the formation of two different 1D complexes {[Cd(bfcs)(C₃H₄N₂)₂] · CH₃OH · 2H₂O}_n (3) and [Cd(bfcs)(CH₃OH)]_n (5). It can be seen from the results that applying different synthetic routes produce dissimilar complexes from however the same materials and under the same reaction conditions. In addition, investigations of differential pulse voltammetry of these four 1D complexes indicate that their half-wave potentials are slightly higher than that of H₂bfcs.     

Synthesis and electrochemical studies of octahedral nickel β-diketonate complexes

The reaction of [Ni(tmhd)₂] and [Ni(dbm)₂] with N-donor chelating ligands in dichloromethane and acetone, respectively, yields the complexes [Ni(tmhd)₂(L-L)] (L-L = 2,2′-bpy 1, phen 2 and dmae 3) and [Ni(dbm)₂(L-L)] (L-L = 2,2′-bpy 4, phen 5, dmae 6). UV-Vis spectroscopy shows very strong bands in the UV region consistent with ligand centred π → π^∗ transitions. The electrochemical studies of 1-6 reveal oxidation to Ni(III). The [Ni(tmhd)₂(L-L)] 1-3 are more easily oxidized by ca. 300 mV and are quasi-reversible whereas for the [Ni(dbm)₂(L-L)] series only complex 6 shows significant reversibility. X-ray crystallographic studies have been conducted in the case of [Ni(dbm)₂(phen)] 5 and [Ni(dbm)₂(dmae)] 6. The structures both show that the nickel metal centre is octahedral with an O₄N₂ coordination environment. In the structures the β-diketonate ligands exhibit a cis-arrangement, with the metal displaced out of the planar chelate ring.     

Self-assembly of three novel mixed-ligand coordination polymers: Formation of 2-D grids, 1-D chains and ladders and crystal band structure

Hydrothermal reaction of the carboxylate-based ligands with metal salts (or oxide) and 4,4′-bipyridine as a second linker, afforded three new coordination polymers, namely, [Co(PCPA)₂(4,4′-bpy)]_n (1) with 2-D rectangle grids, Cu(PCPA)₂(4,4′-bpy)]_n (2) with a linear chain, [Ag(PCPA)(PCPAH)(4,4′-bpy) · H₂O]_n (3) with 1-D molecular ladder (4,4′-bpy = 4,4′-bipyridine; PCPA = p-chlorophenoxyacetate; PCPAH = p-chlorophenoxyacetic acid). It is noticeable that compound 3 is also a supramolecular framework built by coordination bonds, weak interactions between Ag ions, π-π stacking interactions and hydrogen-bonded interactions. The three compounds with different structure motifs have been characterized by elemental analyses, IR spectra, ultraviolet-visible diffuse reflection integral spectra, fluorescent spectra and single crystal X-ray diffraction analysis. Furthermore, the bonding properties of compound 3 were investigated in terms of the absorption spectrum, as well as the calculated band structures and density of states.     

Synthesis and characterization of two new metal-organic materials based on In/btec

Two new metal-organic materials, In(2,2′-bipy)(btec)_0.5Cl (1) and In₂(phen)₄(Hbtec)₂ (2) (btec = 1,2,4,5-benzenetetracarboxylate, 2,2′-bipy = 2,2′-bipyridyl, phen = 1,10-phenanthroline) have been synthesized under mild hydrothermal condition. Their structures were determined by single-crystal X-ray diffraction and further characterized by X-ray powder diffraction, thermogravimetric analysis, IR, fluorescence spectroscopy, inductively coupled plasma (ICP) and elemental analysis. The structural analysis reveals that compound 1 exhibits a novel wavelike 2D layer with unusual contorted rhombic grids, while compound 2 possesses dinuclear In₂(phen)₄(Hbtec)₂ complex molecules. It is noteworthy that their structures finally extend to the higher dimensional supramolecular framework structures through the π-π stacking interactions of N-donor ligands. Additionally, these two compounds show strong fluorescence in the solid state at room temperature.     

Supramolecular assembly driven by hydrogen-bonding and π-π stacking interactions based on copper(II)-terpyridyl complexes

Six 2D and 3D supramolecular complexes [Cu(L1)(O₂CCH₃)₂] · H₂O (1), [Cu₂(L2)₂(μ₂-O₂CCH₃)₂](BF₄)₂ (2), [Cu₂(L1)₂(BDC)(NO₃)₂] · 0.5H₂O (3) [Cu₂(L2)₂(BDC)(NO₃)₂] (4), [Cu₂(L3)₂(BDC)(NO₃)₂] · 0.5H₂O (5) and [Cu₂(L2)₂(BDC)(H₂O)₂](BDC) · 8H₂O (6) (L1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, L2 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine, L3 = 4′-phenyl-2,2′:6′,2″-terpyridine, BDC = 1,4-benzenedicarboxylate), have been prepared and structurally characterized by X-ray diffraction crystallography. In complexes 1, 3, and 4, 1D channels are formed through C-H?O and C-H?N hydrogen-bonding interactions, and further linked into 3D structure via C-H?O and O-H?O interactions. Complex 2 is a 2D layer constructed from intermolecular C-H?F and π-π stacking interactions. In the structure of 6, the BDC²⁻ ions and solvent water molecules form a novel 2D layer containing left- and right-handed helical chains via hydrogen-bonds, and an unusual discrete water octamer is formed within the layer. In 2, 4, 6 and [Ag₂(L2)₂](PF₆)₂ (7) the bonding types of pendent pyridines of L2 depending on the twist about central pyridines are involved in intramolecular (2 and 4), intermolecular (6) or coordination bonds (7) in-twist-order of 5.8°, 3.7°, 28.2° and 38.0°, respectively. Differently, the pendent pyridines of L1 in 1 and 3 form intermolecular hydrogen bonds despite of distinct corresponding twist angles of 25.1° (1) and 42.6°(3). Meanwhile, π-π stacking interactions are present in 1-6 and responsible for the stabilization of these complexes.     

Hydrothermal synthesis and crystal structure of one-dimensional organic/inorganic hybrid material: [Mo4O12(2,2′-bpy)3]n

A new polyoxomolybdenum compound [Mo₄O₁₂(2,2′-bpy)₃]_n (1) (2,2′-bpy = 2,2′-bipyridine) has been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, and single crystal X-ray diffraction. The solid state structure is a 1D chain with a repeat unit of three corner-sharing {MoO₄N₂} octahedra and one {MoO₄} tetrahedron.     

Synthesis, characterization and properties of series coordination polymers constructed from a biphenyl dicarboxylate and nitrogen-containing mixed ligands

A series of coordination polymers have been prepared by the combination of flexible ligand 1,1′-biphenyl-2,2′-dicarboxylic acid (H₂dpa) and different types of nitrogen-containing ligands, with various metal ions such as Co(II), Zn(II) and Cd(II). The single-crystal structure analyses reveal that the above complexes possess different structure features with the introduction of different nitrogen-containing ligands. When auxiliary linear ligand 4,4′-bipyridine (4,4′-bpy) is introduced, two-dimensional layered complex, [Co₂(dpa)₂(4,4′-bpy)₂(H₂O)]_n (1) is formed. Whereas if chelating ligand, 1,10-phenanthroline (1,10′-phen) and 2,2′-bipyridine (2,2′-bpy) are introduced, one-dimensional complex [Zn(dpa)(1,10′-phen)]_n (2) and discrete complexes [Co₂(dpa)₂(2,2′-bpy)₂(H₂O)₂] (3), [Co₃(dpa)₃(1,10′-phen)₆(H₂O)₂] (4), [Cd(dpa)(1,10′-phen)₂][(H₂dpa)₂(H₂O)₂] (5) are synthesized. To our interest, 1 and 2 crystallize in homochiral spacegroup. Furthermore, the magnetic property of complex 1 and the fluorescent properties of complexes 2 and 5 are studied.     

New photoluminescence coordination polymers constructed from different ligands, which are generated from maleic acid at hydrothermal conditions

A new coordination polymer, [Zn₂(mal)(1,10-phen)Cl]_n (1), (mal = malate, 1,10-phenanthroline), has been synthesized with malic acid and fumaric acid which are generated from maleic acid under hydrothermal reactions. At about the same condition, we get [Cd(fma)(2,2′-bpy)(H₂O)]_n (2) (fma = fumarate, 2,2′-bpy=2, 2′-bipyridine). The diverse products illustrate that the carbon-carbon doublebond of the maleic acid has two kinds of reaction trends under different conditions. Complex 1, which displays a two-dimensional (4, 8) lattice-type network, is formed from Zn and maleic through the addition reaction with water molecule. If the Zn is changed by Cd, at the same reaction condition with 1, a two-dimensional supramolecular network complex 2 is formed through the conformation transform reaction. To our knowledge, a lot of coordination polymers have been constructed from malic acid and fumaric acid directly; however, these kinds of complexes have seldom been synthesized from maleic acid under hydrothermal reaction. As is known, the rigid carbon-carbon double bond makes maleic acid lead to some unique structural features which the saturated aliphatic acid does not possess. To illustrate this clearly, a simple one dimensional complex 3, [Cd(glut)(1,10-phen)(H₂O)]_n (glut = glutarate), is synthesized. Furthermore, complex 1 and complex 3 exhibit intense photoluminescent property at room temperature.     

Synthesis, photoluminescence and electrochemiluminescence of ruthenium(II) polypyridyl complexes based on bipyridine derivatives with carbazole moieties

Six complexes (1-6) with the type of [Ru(bpy)₂L]X₂ (1-3: L = L1-L3, X = Cl⁻; 4-6: L = L1-L3, X = PF₆⁻) were synthesized based on 2,2′-bipyridine and three 2,2′-bipyridine derivatives L1, L2 and L3 (L1 = 5,5′-dibromo-2,2′-bipyridine, L2 = 5-bromo-5′-carbazolyl-2,2′-bipyridine, L3 = 5,5′-dicarbazolyl-2,2′-bipyridine). The complexes 1-6 were characterized by ¹H NMR, MS(ESI) and IR spectra, along with the X-ray crystal structure analysis for 1, 5 and 6. Their photophysical properties and electrochemiluminescence (ECL) properties were investigated in detail. In the UV-Vis absorption spectra, all complexes 1-6 show strong intraligand (π → π^∗) transitions and metal-ligand charge transfer (MLCT, dπ (Ru) → π^∗) bands. Upon the excitation wavelengths at ∼508 nm, all complexes 1-6 exhibit typical MLCT emission of ruthenium(II) polypyridyl complexes. The introduction of carbazole moieties improves the MLCT absorption and emission intensity. The ruthenium(II) complexes 1-6 exhibit good electrochemiluminescence (ECL) properties in [Ru(bpy)₂L]²⁺/tri-n-propylamine (TPrA) acetonitrile solution and the complexes with PF₆⁻ showed higher ECL emission intensity than that of the complexes with Cl⁻ based on the same ligands.     

New polyoxometalate-templated supramolecular networks based on transition metal ions and pyridine-N-oxide ligands

Two new complexes, [Cu(bppdo)(Hbppdo)(CH₃CN)₃][PW₁₂O₄₀]·CH₃CN·0.5H₂O (1) and [Co(2,2′-bpdo)₃]₂[PW^VW^VI₁₁O₄₀]·CH₃CN·2H₂O (2) (bppdo = 1,3-bis(4-pyridyl)propane-N,N′-dioxide, 2,2′-bpdo = 2,2′-bipyridine-N,N′-dioxide), have been synthesized by layering MHPW₁₂O₄₀ salts (M = Cu²⁺ for 1 and Co²⁺ for 2) on the organic bppdo (for 1) or 2,2′-bpdo (for 2) ligands with the mixed media of acetonitrile and water at room temperature. Both complexes were fully characterized by elemental analyses, TG analyses, IR, UV-Vis, cyclic voltammetry and single-crystal X-ray diffraction. Both crystal structures exhibit the new polyoxometalate (POM)-templated supramolecular network arrays. The “host” supramolecular networks with large pores are composed of the [Cu(bppdo)(Hbppdo)(CH₃CN)₃] ring-connected-ring chains for 1 and the [Co(2,2′-bpdo)₃] windstick-type units for 2. The “guest” Keggin-type polyoxoanions are located in the pores and dispersed between two organic layers in both complexes. Electrochemical properties of 1 and 2 were investigated and both compounds show the electrocatalytic activity towards the reduction of nitrite.     

Cation control of dimensionality in isothiocyanate coordination polymers constructed from conformationally flexible 3,3′-bipyridine tethers

Two isothiocyanate coordination polymers constructed from the conformationally flexible tethering ligand 3,3′-bipyridine (3,3′-bpy) and divalent metal cations have been prepared and characterized via single crystal X-ray diffraction, infrared spectroscopy and elemental analysis. [Co(NCS)₂(3,3′-bpy)₂] (1), wherein the isothiocyanate ligands are coordinated in a trans fashion, manifests stacked two-dimensional (2-D) rhomboid grid layered motifs. In contrast, [Ni(NCS)₂(3,3′-bpy)₂] (2) possesses a doubly interpenetrated adamantoid three-dimensional (3-D) network despite the presence of trans isothiocyanate ligands. Thus, a metal cation-based control of coordination polymer dimensionality has been revealed in this system, reflective of different donor dispositions allowed by the conformational flexibility of the exobidentate 3,3′-bpy ligand. The 3-D framework of 2 decomposes at a temperature ∼40 °C higher than the 2-D network of 1.