Two unprecedented 1D coordination polymer chains based on tetranuclear copper(II) building blocks

The reaction of copper(II) sulfate with pyridine in DMF or methanol yield two unprecedented Cu(II) coordination polymers {[Cu₄(μ₄-O)(py)₄(SO₄)₄][μ-Cu(py)(DMF)₂]}_n(1) and {[Cu₄(μ₄-O)(py)₄(SO₄)₄][μ-Cu(py)₄]}_n(2), respectively. Single-crystal X-ray diffraction indicated that compound 1 crystallizes in the monoclinic system, space group p2(1)/n, a=14.542(5) Å, b=16.359(5) Å, c=18.951(5) Å, β=92.047(5)°, V=4505(2) Å³, Z=4 while 2 is monoclinic C2/c, a=23.078(5) Å, b=10.214(5) Å, c=23.142(5) Å, β=115.471(5)°, V=4925(3) Å³, Z=4. Both of the two compounds consist of tetrahedral tetranuclear [Cu₄(μ₄-O)(py)₄(SO₄)₄] clusters that are bridged by pentacoordinated Cu atom for 1 or hexacoordinated Cu atoms for 2 through the sulfate oxygen to form the infinite one-dimensional polymer chains.     

A small methanoato ligand in the structural differentiation of copper(II) complexes

Several copper(II) methanoato complexes, namely mononuclear [Cu(O₂CH)₂(2-mpy)₂] (1) (2-mpy = 2-methylpyridine), binuclear [Cu₂(μ-O₂CH)₄(2-mpy)₂] (2), and the polynuclear {[Cu(μ-O₂CH)₂(2-mpy)₂][Cu₂(μ-O₂CH)₄]}_n (3) and {Na₂[Cu(μ-O₂CH)₂(O₂CH)₂][Cu₂(μ-O₂CH)₄]}_n (4), have been synthesized. The mononuclear complex 1 is formed by two asymmetric chelate methanoate anions and two 2-methylpyridine molecules, giving a highly distorted ‘elongated octahedral’ coordination sphere. Complex 1 decomposes outside the mother-liquid, transforming into a regular isolated binuclear paddle-wheel complex 2 with four intra-binuclear bridging methanoates and two axial 2-mpy ligands. The polynuclear complex 3 is formed of alternate mononuclear and binuclear building blocks resembling the central cores of 1 and 2, but with significant differences, especially for the methanoates of the mononuclear units. The oxygen atom of the mononuclear unit in the octahedral axial position in 3 is simultaneously coordinated to the axial position of the binuclear paddle-wheel central core, thus enabling a chain type of structure. A chain of alternate mononuclear and binuclear building blocks, as in the neutral compound 3, are found as well in the ionic polymeric compound 4, though two types of bridges are found in 4, while there is only one type in 3. Namely, the axial position of the octahedral mononuclear unit in 4 is occupied by the methanoate oxygen atom that is already a part of the binuclear paddle-wheel unit, while one equatorial methanoate from the mononuclear unit serves as a triatomic bridge to the axial position of the binuclear building block. A very strong antiferromagnetic interaction is found for all the complexes with the paddle-wheel building blocks [Cu₂(μ-O₂CH)₄] 2–4 (−2J = 444–482 cm⁻¹), attributed to the methanoate intra-binuclear bridges. On the other hand, this strong antiferromagnetism, found already at room temperature, reduces the intensity of the EPR S = 1 spin signals reported for the isolated paddle-wheel complex 2. For the polymeric 3, only the spin S = ½ signals are found in the EPR spectra, and they are assigned to the mononuclear building blocks. No signals with a clear origin are however seen in the room temperature EPR spectrum of the polymeric analogue 4, only the S = ½ signals in the low temperature spectra. This feature is suggested to be due to a specific influence between the adjacent S = 1 (binuclear) and S = ½ (mononuclear) species via their bridges.     

Metal-biradical chains from a high-spin ligand and bis(hexafluoroacetylacetonato)copper(II)

The synthesis, X-ray crystal structure, and magnetic studies of a rare example of organic/inorganic spin hybrid clusters extended in infinite ladder-type chain [Cu(C5F6HO2)2]7(C35H35N5O4)2 ([Cu(hfac)2]7(pyacbisNN)2, 2) formed by the reaction of a high spin nitronylnitroxide biradical C35H35N5O4 (pyacbisNN, 1) and bis(hexafluroacetylacetonate)copper(II) = Cu(hfac)2 are described. Single-crystal X-ray structure analysis revealed the triclinic P1 space group of 2 with the following parameters: a = 10.6191(4) A, b = 19.6384(7) A, c = 21.941(9) A, alpha = 107.111(7) degrees, beta = 95.107(8) degrees, gamma = 94.208(0) degrees , Z = 2. Each repeating unit in 2 carries a centrosymmetric cyclic six spin and a linear five spin cluster with four different copper coordination environments having octahedral and square planar geometries. These clusters are interconnected to form infinite chains which are running along the crystallographic b axis. The magnetic measurements show nearly paramagnetic behavior with very small variations over a large temperature range. The magnetic properties are thus result of complex competitions of many weak ferro- and antiferromagnetic interactions, which appear as small deviations from quite linear mu(eff) vs T dependence at low temperature. At high temperature (300-14 K), antiferromagnetic behavior dominates a little, while at very low temperature (14-2 K), a small increase of mu(eff) was observed. The magnetic susceptibility data are described by the Curie-Weiss law [chi = C/(T - theta)] with the optimal parameters C = 4.32 +/- 0.01 emuK/mol and theta = - 0.6 +/- 0.3 K, where C is the Curie constant and theta is the Weiss temperature.     

Structural variation from 1D to 3D: effects of ligands and solvents on the construction of lead(II)-organic coordination polymers

A series of Pb(II) coordination polymers [Pb(ndc)(dpp)] (1), [Pb(ndc)(ptcp)].0.5 H2O (2), [Pb(ndc)(dppz)] (3), [Pb(ndc)(tcpn)(2)] (4), [Pb2(ndc)2(tcpp)] (5), [Pb(Hndc)2].H2O (6), [Pb(ndc)(dma)] (7), [Pb(bdc)(dma)] (8), [Pb(trans-chdc)(H2O)] (9), and [Pb2(cis-chdc)2].NH(CH3)2 (10), where ndc=1,4-naphthalenedicarboxylate, dpp=4,7-diphenyl-1,10-phenanthroline, ptcp=2-phenyl-1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene, dppz=dipyrido[3,2-a:2',3'-c]phenazine, tcpn=2-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)naphthol, tcpp=4-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)phenol, dma=N,N-dimethylacetamide, bdc=1,4-benzenedicarboxylate, and chdc=1,4-cyclohexanedicarboxylate, have been synthesized from a hydrothermal or solvothermal reaction system by varying the ligands or the solvents. Compounds 1-5 crystallize with an N-donor chelating ligand and an aromatic dicarboxylate linker. Compounds 1-4 are 1D polymers with different pi-pi stacking interactions, whereas compound 5 consists of 2D layers. The structures of compounds 7, 8, and 10 are 3D frameworks formed by connection of the Pb(II) centers by organic acid ligands. Compound 7 is chiral although the ndc ligand is achiral, while the framework of 8 is a typical 3D (3,4)-connected net. Compound 10 is the first example of Pb(II) wheel cluster [Pb(8)O(8)] units bridged by carboxylate groups. Compound 6 contains 1D chains which are further extended to a 3D structure by pi-pi interactions. Compound 9 consists of a 2D network constructed by Pb(II) centers and trans-chdc ligands. The structural differences between 7 and 8 and between 9 and 10 indicate the importance of solvents for framework formation of the coordination polymers. By varying the solvent the cis and trans conformations of H(2)chdc in 9 and 10 were separated completely. The photoluminescence and nonlinear optical properties of the coordination polymers have also been investigated.     

One-dimensional hydrogen-bonded infinite chains composed of nickel(II) and copper(II) tetraaza macrocyclic complexes with cyclopropane-1-carboxylic acid-1-carboxylate ligand

The reaction of [M(L)]Cl₂ · 2H₂O (M = Ni²⁺ and Cu²⁺, L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) with 1,1-cyclopropanedicarboxylic acid (H₂-cpdc) generates one-dimensional hydrogen-bonded infinite chains [Ni(L)(H-cpdc)₂] (1) and [Cu(L)(H-cpdc)₂] (2) (H-cpdc = cyclopropane-1-carboxylic acid-1-carboxylate). These complexes have been characterized by X-ray crystallography, spectroscopy, and cyclic voltammetry. The crystal structures of (1) and (2) show a distorted octahedral coordination geometry around the metal ion, with four secondary amines and two oxygen atoms of the H-cpdc ligand at the trans position. Complexes (1) and (2) display the one-dimensional hydrogen-bonded infinite chains. The cyclic voltammogram of the complexes display two one-electron waves corresponding to M^II/M^III and M^II/M^I processes. The electronic spectra and electrochemical behavior of the complexes are significantly affected by the nature of the axial H-cpdc ligand.     

1D coordination polymers of silver(I) and copper(II) based on bis(N-heterocyclic carbene) ligands: Synthesis and structural studies

The alkyl chain-linked diimidazolium (or dibenzimidazolium) salts, 1,1′-diethyl-4,4′-tetramethylene-diimidazolium-diiodide (L¹H₂·I₂) and 1,1′-diethyl-3,3′-trimethylene-dibenzimidazolium-diiodide (L²H₂·I₂), and their silver(I) and copper(II) coordination polymers, [L¹AgI]_n (1) and [L²Cu₂I₄]_n (2), have been prepared and characterized. Complex 1 is a 1D helical polymer generated by bidentated carbene ligands (L¹) and Ag(I) atoms. The 1D polymer of 2 is formed by bidentated carbene ligands (L²) and coplanar quadrilateral Cu₂I₂ units. 3D supramolecular frameworks in the crystal packings of 1 and 2 are formed via intermolecular weak interactions, including C–H···π contacts, π–π interactions and C–H···I hydrogen bonds.     

Conformation change of the cyclohexanedicarboxylate ligand toward 2D and 3D La(III)-organic coordination networks

2D and 3D structures of La-1,4-cyclohexanedicarboxylates (chdc) coordination networks, have been constructed using flexible chdc ligands which can have cis and trans conformations of two dicarboxylate groups, controlled by the solution pH in hydrothermal reaction conditions.     

3D sandwich-like frameworks constructed from silver chains: synthesis and crystal structures of six silver(I) coordination complexes

The reaction of AgNO₃ with combinations of 4,4′-bipyridine (bpy), 1,2-di(4-pyridyl)ethane (dpe), 1,3-bis(4-pyridyl)propane (bpp), succinic acid (H₂su), terephthalic acid (H₂tp), 2,2′-diphenylaminedicarboxylic acid (H₂dpadc), and naphthaleneacetic acid (Hnaa) in aqueous alcohol at room temperature produces block-like crystals of [Ag₃(bpy)₃](su)·10H₂O, [Ag₂(bpy)₂](tp)·6H₂O, [Ag₂(dpe)₂(H₂O)₂](dpadc)·H₂O, [Ag₆(dpe)₆(H₂O)₄](tp)₃·12H₂O, [Ag(bpp)](naa), and [Ag₂(bpp)₂](dpadc)·6H₂O. All six compounds consist of 1D infinite silver-bpy/dpe/bpp cationic chains, interspersed with organic carboxylate anions that provide charge compensation in the crystal structures. The lattice water molecules are situated among the framework of the crystal structure and show rich hydrogen-bonding interactions {except for [Ag(bpp)](naa)}, which help to orientate of the organic carboxylate anions in the crystal packing.     

1D coordination polymers of Cu(II) and Cu(II) dimers with a dicyanomethanide ligand

Several new 1D coordination polymers have been synthesised using the anionic ligand carbamoyldicyanomethanide, C(CN)₂(CONH₂)⁻ (cdm). The polymeric complexes [Cu(cdm)₂(py)₂]·2MeOH (1), [Cu(cdm)₂(4-Etpy)₂]·2MeOH (2), [Cu(cdm)₂(3,5-Me₂pzH)₂]·2MeOH (3) and [Cu(cdm)₂(3-HOCH₂py)₂]·2MeOH (4) (py = pyridine; 3,5-Me₂pzH = 3,5-dimethylpyrazole) contain Cu(II) atoms bridged by μ₂-(N,N′) cdm ligands between equatorial and axial coordination sites. The use of monodentate co-ligands brings about polymeric products, in contrast to the use previously of chelating co-ligands which facilitate the formation of discrete products. These 1D polymeric complexes are connected by hydrogen bonding between the amide functionalities and the lattice solvent. In the structures of 3 and 4 the neutral ligands also contain hydrogen bond donor groups that supplement the amide ring motif. Two other complexes have been obtained that are polymeric chains of alkoxide-bridged Cu(II) dimers. The complexes [Cu(cdm)(MeO)(2-amp)] (5) and [Cu(cdm)(dmap)] (6) (2-amp = 2-(aminomethyl)pyridine and dmap = dimethylaminopropoxide) are remarkably similar despite the different ligands that they contain. Bridging between dimers is via μ₂-(N,O) cdm ligands, consequently altering the nature of the hydrogen bonding between adjacent chains compared to the simple polymeric species 1–3.     

Synthesis, characterization and structural analysis of new copper(II) complexes incorporating a pyridoxal-semicarbazone ligand

The reaction between 3-hydroxy-5-hydroxymethyl-2-methyl-4-pyridinecarboxaldehyde semicarbazone (pyridoxal-semicarbazone or PLSC) and appropriate chloride, sulfate, nitrate or thiocyanate Cu(II) salts in water/alcohol mixtures resulted in the formation of new copper(II) complexes: [Cu(PLSC)Cl₂] (1), [Cu(PLSC)(H₂O)(SO₄)]₂·3H₂O (2), [Cu₂(PLSC)₂(NCS)₂](NCS)₂ (3), [Cu(PLSC)(NO₃)₂(CH₃OH)] (4) and [Cu(PLSC-2H]NH₃·H₂O (5). The complexes were characterized by elemental analysis, conductometric measurements and IR spectroscopy, while complexes 1, 2, 3 and 4 were further characterized by single crystal X-ray diffraction.     

Distorted pentacoordinate copper(II) complexes containing a tridentate ligand

Summary Copper(II) complexes with a tridentate chelating ligand within the general 2N, X (X = O or S) donor class, containing abis(benzimidazolyl) donor set, were prepared and characterized. X-band e.p.r. spectra of the complexes indicateg >g and the largeg and lowA have been interpreted in terms of a distorted basal plane. Superimposed on theg component are five SHF lines withA _N = 16±2G, supporting the interaction of two nitrogen atoms with the copper nucleus. Thus, the basal plane of the complex comprises 2N atoms, with the ligand hetero atom being axially coordinated.     

Bispidine copper(II) compounds: effects of the rigid ligand backbone

Approximative density-functional theory calculations indicate that the tetradentate ligand L (L = 2,4-bis-(2-pyridyl)-3,7-diaza-[3.3.1]-bicyclononane) enforces an unusual and strong binding of a co-ligand (substrate) to a copper(II) center. The co-ligand in [Cu(L)(Cl)](+) completes a square-pyramidal coordination around copper(II) and binds in the equatorial plane rather than on the apical position. This configuration is a stable geometric isomer for the model complex [Cu(NH3)2(imine)2(Cl)](+), but it is disfavored by approximately 10 kJ mol(-1) and not commonly observed for CuN4 chromophores with a monodentate co-ligand. The equatorial coordination increases the bond energy of the copper(II)-chloride bond by approximately 80 kJ mol(-1), and similar results are expected for other copper(II)-L-substrate complexes, some of which show strong catalytic activity or unusual stability. Despite the enforced configuration, L does not impose significant steric strain on the copper(II) center but is well preorganized for the Jahn-Teller labile ion in this unusual geometry. The preorganization extends to the orientation of the pyridine donors (torsion angle around the copper-pyridine bond), and this seems to be of importance in the reactivity of the copper-L complexes and their derivatives.     

Extended chains via hydrogen bond linkages of dinuclear copper(II) and cadmium(II) complexes with a new flexible disulfoxide ligand

A new flexible disulfoxide ligand 1,6-bis(benzylsulfinyl)hexane (L), which is a mixture of the meso and rac isomers, was treated with Cu^II or Cd^II nitrate and obtained dimeric complex [Cu₂(L)₃(H₂O)₂(NO₃)₄] 2 or [Cd₂(L)₃(H₂O)₂(NO₃)₄] 3. In the reacting system the crystals of meso isomer 1 of L together with 2 or 3 were obtained. 2 and 3 have similar molecular structures. In the neutral dimer, three ligands present two kinds of coordination models: monodentate and bis-monodentate. The neutral dimeric units in 2 and 3 are linked by hydrogen bonds to yield a chain structure. Crystal structures of all three compounds were determined by single-crystal X-ray diffraction methods. Crystal data for 1: monoclinic, space group Cc, a=41.95(2), b=5.132(2), c=8.660(4) Å, β=94.898(9)°, V=1857.7(15) Å³, Z=4, final refinement (I>2σ(I)): R1=0.0659, wR2=0.1415. Crystal data for 2: triclinic, space group P-1, a=9.242(4), b=9.539(4), c=21.042(9) Å, α=83.888(9), β=87.971(8), γ=74.177(9)°, V=1774.6(13) Å³, Z=2, final refinement (I>2σ(I)): R1=0.0577, wR2=0.0954. Crystal data for 3: triclinic, space group P-1, a=9.203(4), b=9.831(3), c=20.860(7) Å, α=84.313(6), β=86.432(7), γ=74.188(6)°, V=1805.9(11) Å³, Z=2, final refinement (I>2σ(I)): R1=0.0548, wR2=0.1192.     

Mixed ligand complexes involved in the system pyridoxamine-glycylglycine-imidazole copper(II)

Ternary as well as quaternary complexes involved in the system pyridoxamine-glycylglycine-imidazole-copper(II) have been studied by pH-metric titration at 37°C and I = 0.15 M (NaNO₃). The data were assessed by program MINIQUAD 75. The formation constants were compared with those obtained from the system of pyridoxamine-glycine-imidazole with some bivalent metal ions previously reported. They are ～ 2.5 log units less. In addition, the enhancement of quaternary complex formation has been described in terms of binary and ternary complex formation reactions. It has been also found that deprotonation of the peptidic proton of glycylglycine took place in the presence of more than one different ligand.     

Cobalt(II), nickel(II) and copper(II) complexes of a Schiff base ligand: synthesis,structural characterization and luminescence properties

A Schiff base ligand (HL), 2,4-dimethoxy-N-(5-chloro-2-hydroxybenzylidene)-benzenamine, derived from 5-chloro-2-hydroxybenzaldehyde and 2,4-dimethoxyaniline, and its metal complexes [Co(L)₂]·CH₃OH (1), [Ni(L)₂] (2), [Cu(L)₂] (3) have been synthesized. The compounds were characterized by analytical and spectroscopic methods. In addition, the structures of the Schiff base HL and its Co(II) complex were determined by single-crystal X-ray analysis. The Co(II) center is six-coordinate, being coordinated to two imine nitrogen, two phenolate oxygen and two methoxy oxygen atoms of two crystallographically independent Schiff base ligands. Luminescence properties of HL and its complexes were investigated both in solution and in the solid state.     

Oxidative degradation of beta-diketiminate ligand in copper(II) and zinc(II) complexes

Copper(II) and zinc(II) complexes supported by a popular beta-diketiminate ligand (1(-), 2-mesitylamino-4-mesitylimino-2-pentene), [CuII(1)(AcO)] and [[ZnII(1)]2(mu-MeO)(mu-AcO)], have been demonstrated to undergo an oxidative degradation to give a ketone diimine derivative (2) under aerobic conditions. The crystal structures of the mononuclear copper(II) and dinuclear zinc(II) complexes of the beta-diketiminate ligand as well as the copper(II) complex of the modified ligand have been determined by X-ray crystallographic analysis. Mechanism for the oxidative degradation reaction of the beta-diketiminate ligand is also discussed.     

Three copper(II) complexes constructed from a new 1,3,5-triazine derivative ligand

Three new complexes {[Cu(dpdapt)(Hhbd)] · 6H₂O}_n (1) (dpdapt = N,N′-di(2-pyridyl)-2,4-diamino-6-phenyl-1,3,5-triazine, Hhbd = 2-hydroxybutanedioicate dianion), [Cu(dpdapt)(SO₄)] · 2H₂O (2) and [Cu(dpdapt)(oxa)] · H₂O (3) (oxa = oxalate dianion) have been synthesized and structurally characterized. The non-covalent interactions of π–π stacking and hydrogen bonding extend complexes 1–3 into supramolecular architectures, where 1 self-assembles into a 1D polymeric chain by dicarboxylate bridges and exhibits a 3D framework with 1D open channels, while complexes 2 and 3 display 2D wavelike networks. Interestingly, in 1, the host framework encapsulates hexameric water clusters that are connected into 1D arrays by supramolecular association along the 1D open channels. The UV/vis, IR spectra, fluorescence and TG analysis for complexes 1, 2 and 3 are also discussed.     

Synthesis of new mixed ligand complexes of copper(II) dithiocarbamates

New mixed ligand complexes of copper(II) dithiocarbamates of the general formula, [CuCl(R₂dtc)L] or [CuCi(R′ dtc)L] (RCH₃ or C₂H₅, R′ = (CH₂)₅, dtc =-NCSS^? and L = Pyridine, 3-picoline or 4-picoline), have been prepared by the reaction of bis(dithiocarbamato)di-μ-chloro-dicopper(II) complexes with pyridine or picolines. The complexes are found to be non-electrolytes in nitrobenzene. Magnetic susceptibilities, i.r. and electronic spectra of the complexes are reported. A psuedo-tetrahedral structure is suggested for these complexes.