Solvothermal syntheses and crystal structures of new Cu(II) complexes with phenylsuccinic acid

Five new Cu(II) complexes [Cu(psa)(phen)] · 3H₂O (1), [Cu(psa)(2bpy)] · 0.5H₂O (2), [Cu(psa)(2bpy)(H₂O)] · 3H₂O (3), [Cu(psa)(4bpy)] · H₂O (4), and [Cu(psa)_0.5(N₃)(2bpy)] (5) (H₂psa = phenylsuccinic acid, phen = 1,10-phenanthroline, 2bpy = 2,2′-bipyridine, and 4bpy = 4,4′-bipyridine) were obtained under solvothermal conditions and characterized by single-crystal X-ray diffraction. Complexes 2 and 3 were formed by one-pot reaction. In complex 2, Cu(II) ion is four-coordinated and locates at a slightly distorted square center. In complex 3, the coordinated water molecule occupies the axial site of Cu(II) ion forming a tetragonal pyramid geometry. Complexes 1 and 3 are of 1D chain structures, and extended into 2D supramolecular network by hydrogen bonds. Complex 2 is of zipper structure, and further assembled into 2D supramolecular network by hydrogen bonds and π–π stacking interactions. Complex 4 is a 3D CdSO₄-like structure with twofold interpenetration, while complex 5 is a dinuclear compound. The different structures of complexes 1–5 can be attributed to using the auxiliary ligands, indicating an important role of the auxiliary ligands in assembly and structure of the title complexes.     

Assembling of copper(II) dipicolinate complexes

The role of ancillary ligands, namely imidazole (im), pyridine (py), 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) in the assembly of copper(II) dipicolinate complexes are presented. Mononuclear complexes are observed in the case of monodentate ligands. The mononuclear complex [Cu(im)₃L]·4H₂O (1) (L = dipicolinate anion) has a distorted octahedral structure with Z′ = 2, whereas [CuL(py)(H₂O)]·2H₂O (2) adopts distorted square pyramidal geometry. The bidentate ligands bpy and phen favor the formation of dinuclear complexes. The dinuclear complex [CuL(bpy)(μ-L)Cu(bpy)(H₂O)]·9H₂O (3) has one carbonyl oxygen atom of a carboxylate group of dipicolinate acting as a bridging ligand to the copper site that is devoid of a coordinated water molecule. The complex has an angle of 83.55° between the plane of L and bpy attached to one copper site, whereas it has an angle of 78.13° between the plane L and bpy attached to the other copper site. A 1,10-phenanthroline containing dinuclear copper(II) dipicolinate complex, [Cu(phen)(H₂O)(μ-L)Cu(phen)₂][CuL₂]·12H₂O (4), has been structurally characterized. It has an unusual carboxylate bridge.     

Mononuclear,dinuclear and hydroxo-bridged tetranuclear complexes from reactions of Cu ions,mandelic acid and diimine ligands

The reaction of copper(II) hydroxocarbonate, mandelic acid (H₂MANO) and 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) in water affords [Cu(bpy)(μ₂-MANO)]₂ · 8H₂O (1), [Cu(bpy)(MANO)] · 4H₂O (2) and the opened tetranuclear hydroxo-bridged copper(II) complexes of formulae [Cu₄(μ₃-OH)₂(μ₂-MANO)₂(bpy)₄](phglyo)₂ · 8H₂O (3) (phglyo = phenylglyoxylate) or [Cu₄(μ₃-OH)₂(μ₂-OH)₂(OH₂)₂(phen)₄](Bza)₂(OH)₂ · 5H₂O (4) (Bza = benzoate), respectively. The compounds have been characterized by spectroscopic techniques and studied by single-crystal X-ray diffractometry. The formation of 3 and 4 takes place in basic media through dehydrogenation or oxidative dehydrogenation followed by in situ oxidative decarboxylation of mandelic acid to phenylglyoxylate or benzoate, respectively. These results indicate that cooperative catalysis of diimine ancillary ligands and copper(II) is essential.     

Synthesis,crystallographic and spectroscopic characterization and magnetic properties of dimer and monomer ternary copper(II) complexes with sulfonamide derivatives and 1,10-phenanthroline. Nuclease activity by the oxidative mechanism

Three dinuclear and one mononuclear copper(II)-1,10-phenanthroline ternary complexes, [Cu(L1)(phen)(OH)]₂ (1), [Cu(L2)(phen)(OH)]₂·3H₂O (2), [Cu(L3)(phen)(OH)]₂ (3) and [Cu(L4)₂(phen)(H₂O)] (4), with thiadiazole sulfonamide derivative ligands: HL1 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)naphthalene-1-sulfonamide), HL2 (N-(5-ethylthio)-1,3,4-thiadiazol-2-yl)-4-methylbenzenesulfonamide), HL3 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide) and HL4 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)-4-methylbenzenesulfonamide) have been synthesized and characterized. In the four complexes each copper atom is five-coordinated. The structure of complexes 1, 2 and 3 consists of a dimeric unit with a C2 symmetry axis, where both coppers are bridged by two hydroxo anions. Magnetic measurements show that the dimer complexes are ferromagnetic according to the Cu–O–Cu angles. Cleavage experiments using pUC18 plasmid DNA in the presence of H₂O₂/ascorbic acid as an activating agent show that the title complexes are potent artificial chemical nucleases, the order of efficiency being 3 > 2 ∼ 1 > 4. Control cleavage experiments indicated that the dimer complexes are stronger artificial nucleases than the [Cu(phen)₂]²⁺ complex under the same experimental conditions, while the monomer 4 has a lower nuclease activity than the [Cu(phen)₂]²⁺ complex. The inhibition of the cleavage process in the presence of reactive oxygen intermediate scavengers suggests that the hydroxyl radical and the superoxide anion are reactive species for the breakage of the DNA strands.     

Preparation,crystal structures and spectroscopic characterization of oxalate copper(II) complexes containing the nitrogen ligands 4,4′-dimethyl-2,2′-bipyridine and di(2-pyridyl)sulfide

The preparation, crystal structures and spectroscopic characterization of four oxalate copper(II) complexes containing the 4,4′-dimethyl-2,2′-bipyridine (Mebpy) or di(2-pyridyl)sulfide (DPS) nitrogen ligands namely [μ-(ox){Cu(Mebpy)(NO₃)(H₂O)}₂] (1), [μ-(ox){Cu(Mebpy)(ClO₄)(H₂O)}₂] (2), [μ-(ox){Cu(DPS)(H₂O)}₂](ClO₄)₂ (3) and [Cu(DPS)(ox)(H₂O)] · 2H₂O (4) are described. X-ray diffraction measurements have shown that complexes 1–3 are binuclear, in which the oxalate anion bridges two Cu(II) centers, while the complex (4) is mononuclear and the oxalate anion adopts the terminal bidentate chelating coordination mode. In 1 and 2 the Cu(II) sites display a distorted octahedral geometry (4+2 environment) and in compounds 3 and 4 the Cu(II) centers exhibit a slightly distorted square pyramidal geometry. In addition, complexes 1 and 2 present a 2D supramolecular arrangement through hydrogen bonds between coordination water molecules and nitrate or perchlorate anions and π-stacking interaction between the pyridyl rings of Mebpy nitrogen ligands.     

Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1,10-phenanthroline)2 building blocks

Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen)₂(H₂O)(HTST)]·2H₂O (1), [Co₃(phen)₆(H₂O)₂(TST)₂]·7H₂O (2), and [Co₂Cu(phen)₆(H₂O)₂(TST)₂]·10H₂O (3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H₃TST) with the M²⁺ (M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). Complex 1 contains a cis-Co(II)(phen)₂ building block and an HTST as monodentate ligand; complex 2 consists of two TST as bidentate ligands connecting one trans- and two cis-Co(II)(phen)₂ building blocks; complex 3 is formed by replacing the trans-Co(II)(phen)₂ in 2 with a trans-Cu(II)(phen)₂, which is the first reported hetero-trinuclear supramolecular complex containing both the Co(II)(phen)₂ and Cu(II)(phen)₂ as building blocks. The study shows the flexible multifunctional self-assembly capability of the H₃TST ligands presenting in these supramolecular complexes through coordinative, H-bonding and even π-π stacking interactions. The photoluminescent optical properties of these complexes are also investigated and discussed as well as the second-order nonlinear optical properties of 1.     

Oxovanadium(IV) and (V) complexes of acetylpyridine-derived semicarbazones exhibit insulin-like activity

Reaction of 2-acetylpyridine semicarbazone (H2APS), 3-acetylpyridine semicarbazone (H3APS) and 4-acetylpyridine semicarbazone (H4APS) with [VO(acac)₂] (acac = acetylacetonate) gave [VO(H2APS)(acac)₂] (1), [VO(H3APS)(acac)₂] (2) and [VO(4APS)(acac)(H₂O)] · 1/2H₂O (3). Oxidation of complex 1 in acetonitrile gave [VO₂(2APS)] (4). The crystal structures of complexes 1 and 4 have been determined. Complexes 1–3 were able to enhance glucose uptake and to inhibit glycerol release from adipocytes, which indicate their potential to act as insulin-mimics.     

Assembly and structures of five new Cu(II) complexes based on the V-shaped building block [Cu(dbsf)]

Five new copper(II) complexes [Cu(dbsf)(H₂O)]_n · 0.5n(i-C₃H₇OH) (1), [Cu(dbsf)(4,4′-bpy)_0.5]_n · nH₂O (2), [Cu(dbsf)(2,2′-bpy)(H₂O)]₂ · (n-C₃H₇OH) · 0.5H₂O (3), [Cu(dbsf)(phen)(H₂O)]₂ · 1.5H₂O (4) and [Cu(dbsf)(2,2′-bpy)(H₂O)]_n · n(i-C₃H₇OH) (5) (H₂dbsf = 4,4′-dicarboxybiphenyl sulfone, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, i-C₃H₇OH = isopropanol, n-C₃H₇OH = n-propanol) have been synthesized under hydro/solvothermal conditions. All of the complexes are assembled from V-shaped building blocks, [Cu(dbsf)]. Complex 1 is composed of 1D double-chains. In complex 2, dbsf²⁻ ligands and 4,4′-bpy ligands connect Cu(II) ions into catenane-like 2D layers. These catenane-like 2D layers stack in an ABAB fashion to form a 3D supramolecular network. Complexes 3 and 4 are 0D dimers, in which two [Cu(dbsf)] units encircle to form dimetal macrocyclic molecules. However, in complex 5, the V-shaped building blocks [Cu(dbsf)] are joined head-to-tail, resulting in the formation of infinite tooth-like chains. The different structures of complexes 3 and 5 may be attributed to the different solvent molecules included.     

Synthesis,structure and biological properties of several binary and ternary complexes of copper(II) with ciprofloxacin and 1,10 phenanthroline

In this study, a new binary complex [Cu(HCip)₂](NO₃)₂ · 6H₂O (1) has been synthesized and then characterized by X-ray structure analyses. In this compound, each ciprofloxacin acts as a bidentate ligand resulting in a crystallographically planar configuration; the nitrate anions are located in apical positions with an axial distance significantly larger than the equatorial distances, which would be consistent with a very weak metal ion interaction due to the Jahn–Teller effect. In addition, both the synthesis and characterization of two new ternary complexes of ciprofloxacin–copper(II)–1,10-phenanthroline, [Cu(phen)(Cip)](NO₃) · 4H₂O (2) and Cu(phen)(HCip)(NO₃)₂ · H₂O (3), have been accomplished. We have also undertaken the single crystal structural determination of 2, in which the ciprofloxacin acts as tridentate bridging ligand; the complex exhibits a five-coordinated motif in a distorted square pyramidal environment around the metal center. The chemical nuclease activity of compounds 2 and 3 has also been studied, revealing that both compounds behave as efficient chemical nucleases in the presence of ascorbate. Mechanistic studies, with various radical oxygen scavengers, indicate that the DNA cleavage reaction is mediated by hydroxyl radicals, singlet oxygen, and the superoxide anion.     

Co(II), Mn(II) and Cu(II) complexes of fluoroquinolones: Synthesis, spectroscopical studies and biological evaluation against Trypanosoma cruzi

[MnCl₂(NOR)(H₂O)₂] (1), [MnCl₂(SPAR)(H₂O)₂] (2), [CoCl₂(NOR)(H₂O)₂] (3) [CoCl₂(SPAR)(H₂O)₂] (4), [CuCl₂(phen)(NOR)] (5) and [CuCl₂(phen)(SPAR)] (6) complexes with norfloxacin (NOR) and sparfloxacin (SPAR) were obtained from MnCl₂·4H₂O, CoCl₂·4H₂O and CuCl₂(phen). In all cases the NOR and SPAR coordinate in the neutral zwitterionic form. The electron paramagnetic resonance spectra of the Cu(II) complexes (5) and (6) in aqueous and DMSO solutions indicate mixture of mononuclear and binuclear complex. Complexes (1-6), together with the corresponding ligands were evaluated for their in vitro trypanocidal effect, against both bloodstream trypomastigotes and intracellular forms of Trypanosoma cruzi. SPAR and NOR were poorly effective upon T. cruzi, complexes (3) and (4) were active against intracellular forms of the parasite. The complexes (5) and (6) displayed a higher activity upon both bloodstream and intracellular forms. The potency of fluoroquinolones, specially those coordinated to Cu(II)-phen justify further trypanocidal screening assays with this compounds in vitro as well as upon experimental models of T. cruzi infection.     

Syntheses,crystal structures and photoluminescence of three coordination polymers with 2,3-pyrazinedicarboxylic acid and N-donor ligands

The reactions between Cd(OAc)₂/Cu(NO₃)₂ and mixed ligands (2,3-pyrazinedicarboxylic acid (pzdc) and N-donor ligands) under different reaction conditions give the three title complexes 1, 2 and 3. There is a (4,8) net 2D network structure and a rectangular grid network structure in the cadmium complexes [Cd(pzdc)(phen)] · H₂O (1) and Cd₂(pzdc)₂(4,4′-bpy)(H₂O)₂ (2), respectively. The complex [Cu₄(pzdc)₄(phen)₂(H₂O)₄] · 10H₂O (3) has a 1D zigzag chain structure. The influences of coordination modes of the pzdc ligand and N-donor ligands on the superstructural diversity have been discussed. Complexes 1 and 2 exhibit strong fluorescent emission bands in the solid state at room temperature. The EPR spectrum of 3 is typical for a square-pyramidal geometry of copper (II) ions.     

Metal–organic frameworks (MOFs) constructed from Zn/Cd-2,2′-bipyridines and polycarboxylic acids: Synthesis,characterization and microstructural studies

Metal–organic frameworks with the compositions [Zn(bpy)(bdc)(H₂O)]_n1, [Zn(bpy)(btec)_1/2(H₂O)]_n2, [Cd(bpy)(bdc)(H₂O)]_n3 and Cd(bpy)(btec)_1/2(H₂O)]_n4 (H₂bdc = 1,4-benzenedicarboxylic acid = terephthalic acid, H₄btec = 1,2,4,5-benzenetetracarboxylic acid and bpy = 2,2′-bipyridine) have been synthesized and characterized using spectroscopic and single-crystal X-ray diffraction techniques. In these complexes, Zn^II/Cd^II-2,2′-bipyridine units and carboxylate anions exists as nodes and spacers respectively. An infinite 1D zig-zag chain structure is observed for both complexes 1 and 3, whereas complexes 2 and 4 display a 3D supramolecular architecture. The complexes are found to be photoluminescent, porous and show significant thermal stability.     

Three new pyridine-2,6-dicarboxylate copper(II) compounds with coordinated pyridine-based ligands: Synthesis, characterisation and crystal structures

Three new Cu(II) compounds of pyridine-2,6-dicarboxylic acid (H₂pdc) with meta-substituted pyridines as additional ligands have been synthesized and structurally characterised using X-ray diffraction. Two of them are mononuclear compounds, i.e. [Cu(pdc)(3acpyr)(H₂O)] (1) (3acpyr = 3-acetylpyridine) and [Cu(pdc)(3HOp)(H₂O)](H₂O)₂ (2) (3HOp = 3-hydroxypyridine). The third compound is polynuclear, i.e. [Cu(pdc)(μ-3HOmp-κN,O)]_n (3) (3HOmp = 3-(hydroxymethyl)pyridine). The three compounds are also characterised by IR, EPR and ligand field spectroscopy. The geometry around the Cu(II) ions is distorted square pyramidal for compounds 1 and 2 and distorted octahedral for compound 3. The lattice of compound 1 is organised by an intra-sheet hydrogen-bond pattern generating double layers. Compound 2 has a lattice arranged by the two water molecules in the lattice with complicated 2D O-H?O intra-sheet hydrogen bonding motifs.The zig-zag chains in compound 3 are further organised in layers, due to the axial coordination at Cu(II), forming a so-called (4, 3) ladder-like one-dimensional coordination polymer. These ladders are interconnected by hydrogen bonding.     

Single stranded helical supramolecular architecture with a left handed helical water chain in ternary copper(II) tryptophan/diamine complexes

The ternary copper(II) complexes [Cu(l-trp)(bpy)](ClO₄) (1) and [Cu(l-trp)(phen)] (ClO₄) · 3H₂O (2) (where l-trp = l-tryptophan, bpy = bipridyl, phen = phenanthroline) have been synthesized. The single crystal X-ray structures for these complexes revealed that the monocationic Cu^II-units are interlinked through Cu–OCO–Cu connectivity and exist as helical coordination polymers. The two different helical strands composed with Cu1 and Cu2 independently, possess a similar pitch distance of 7.713 Å in complex 1. For complex 2, existing in the hydrated form, the Cu(II) polymeric strand and the hydrated water molecules have gained a supramolecular helical architecture with a similar pitch distance of 8.133 Å. The two helical strands in complex 1 are associated with right handed (PP) supramolecular chirality, while the helical water chain and the Cu^II-strand in 2 are self assembled into left handed (MM) helicity in the solid state. The solid state CD recorded for 1 and the dehydrated form of 2 exhibit a positive optical sign at their respective d–d band [λ_max = 667 nm, 1; λ_max = 630 nm, 2], the solution state CD for both these complexes are found to be inverted into a negative optical sign, which could be attributed to inversion of their associated supramolecular helicity. The TGA curve illustrates two distinct weight losses at 60 °C and 87 °C, equivalent to one and two water molecules, respectively. The PXRD pattern for the hydrated and dehydrated forms of 2 indicated a change, on comparison with the simulated diffractograph. The fluorescence properties of both these complexes, possessing tryptophan and bipy/phen, were investigated.     

Synthesis,structure and properties of some copper(II) complexes containing an ONO donor Schiff base and substituted imidazole ligands

Five new mixed ligand coper(II) complexes, viz. [Cu(SAA)(H₂O)] (1), [Cu(SAA)(MeImH)] (2), [Cu(SAA)(EtImH)] (3), [Cu(SAA)(BenzImH)] (4) and [Cu(SAA)(MebenzImH)] (5), where SAA = salicylideneanthranilic acid, MeImH = 2-methylimidazole, EtImH = 2-ethylimidazole, BenzImH = benzimidazole, MebenzImH = 2-methylbenzimidazole, have been synthesized and characterized by means of elemental analysis, FAB mass spectrometry, magnetic susceptibility, X-band EPR, electronic spectroscopy, IR and cyclic voltammetry. The frozen solution EPR spectra of the complexes have shown axial features. Single crystal X-ray analysis of 2 and 3 has revealed the presence of a distorted square planar geometry (N₂O₂) in the complexes. The superoxide dismutase (SOD) activity of the present complexes has also been measured and discussed.     

Novel octahedral nickel(II) dithiocarbamates with bi- or tetradentate N-donor ligands: X-ray structures of [Ni(Bzppzdtc)(phen)2]ClO4 · CHCl3 and [Ni(Bz2dtc)2(cyclam)]

A series of novel octahedral nickel(II) dithiocarbamate complexes involving bidentate nitrogen-donor ligands (phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) or a tetradentate ligand (cyclam = 1,4,8,11-tetraazacycloteradecane) of the composition [Ni(BzMetdtc)(phen)₂]ClO₄ (1), [Ni(Pe₂dtc)(phen)₂]ClO₄ (2), [Ni(Bzppzdtc)(phen)₂]ClO₄ · CHCl₃ (3), [Ni(Bzppzdtc)(phen)₂](SCN) (4), [Ni(BzMetdtc)(bpy)₂]ClO₄ · 2H₂O (5), [Ni(Pe₂dtc)(cyclam)]ClO₄ (6), [Ni(BzMetdtc)₂(cyclam)] (7), [Ni(Bz₂dtc)₂(cyclam)] (8) and [Ni(Bz₂dtc)₂(phen)] (9) (BzMetdtc = N,N-benzyl-methyldithiocarbamate(1-) anion, Pe₂dtc = N,N-dipentyldithiocarbamate(1-) anion, Bz₂dtc = N,N-dibenzyldithiocarbamate(1-) anion, Bzppzdtc = 4-benzylpiperazinedithiocarbamate(1-) anion), have been synthesized. Spectroscopic (electronic and infrared), magnetic moment and molar conductivity data, and thermal behaviour of the complexes are discussed. Single crystal X-ray analysis of 3 and 8 confirmed a distorted octahedral arrangement in the vicinity of the nickel atom with a N₄S₂ donor set. They represent the first X-ray structures of such type complexes. The catalytic influence of complexes 2, 3, 6, and 7 on graphite oxidation was studied and discussed.     

A systematic investigation of the CuCl2/H2mal/phen reaction system (H2mal = malonic acid): Solution and solid state studies of its products

The systematic investigation of the parameter space of the CuCl₂/H₂mal/phen reaction system in MeOH resulted in the isolation of seven different complexes either as mixtures or in pure form, six of which have been structurally characterized. The molar ratios of the reactants and the crystallization methods have been systematically varied, leading to the isolation of compounds [Cu(H₂O)(phen)(mal)] (1), [Cu(MeOH)(phen)(mal)] (2), [Cu₂Li₂Cl₂(phen)₂(mal)₂(MeOH)₄] (3), [Cu₂(phen)₄(mal)][CuCl(phen)(mal)](OH) (4), [CuCl(phen)₂]Cl (5), and [CuCl(phen)(mal)][CuCl(phen)₂][Cu(phen)₂(Hmal)]Cl (6). The coordination versatility of the malonato ligand has been confirmed by the presence of three different coordination modes and its two deprotonation states in compounds 1–6. Solution studies on methanolic solutions of 2–4 and 6 by mass spectrometry revealed the absence of parent ion peak and the presence of fragment ions of low relative abundance not previously found in their crystal structure, thus indicating decomposition and rearrangement/reorganization of the complexes in solution and confirming the dynamic character of their solutions. Compounds 3 and 4 have been also studied in the solid state by EPR spectroscopy and magnetic measurements.     

Structural,spectroscopic and redox properties of transition metal complexes of dipyrido[3,2-f:2′,3′-h]-quinoxaline (dpq)

The chemistry of first row transition metal complexes obtained from the ligand dipyrido[3,2-f:2′,3′-h]-quinoxaline (dpq) have been reported. The reaction between Cu(ClO₄)₂ · 6H₂O with dpq under different reaction conditions led to the isolation of three polymorphic copper(II) complexes [Cu(dpq)₂(H₂O)](ClO₄)₂ · H₂O (2), [Cu(dpq)₂(ClO₄)](ClO₄) (3) and [{Cu(dpq)₂(H₂O)}{Cu(dpq)₂(ClO₄)}](ClO₄)₃ (4). The bluish-green compound 2, obtained by reacting Cu(ClO₄)₂ · 6H₂O with dpq in methanol, has a distorted trigonal bipyramidal structure with τ = 0.55. The reaction between Cu(ClO₄)₂ · 6H₂O and dpq in dry acetonitrile produced the blue compound 3 in which the copper(II) centre has a distorted square planar geometry. When the condensation reaction between 1,10-phenanthroline-5,6-dione and 1,2-diaminoethane was carried out in the presence of Cu(ClO₄)₂ · 6H₂O in methanol, the green copper(II) complex 4 was isolated along with 1. The structure determination of 4 has established the presence of two different complex cations in the asymmetric unit and they are considered as co-crystals. In the zinc(II) compound [Zn(dpq)₂(ClO₄)₂] (5), the two perchlorates are unidentately coordinated to the metal centre, providing a distorted octahedral geometry. The quinoxaline ring in 5 is involved in intermolecular π–π interactions, leading to the generation of a sinusoidal chain. The proton NMR spectra, especially those of the paramagnetic complexes [Ni(dpq)₃](ClO₄)₂ (6) and [Co(dpq)₃](ClO₄)₂ (7), have been studied in detail. The electronic absorption spectra and the redox behaviour of the copper(I), copper(II), cobalt(II) and cobalt(III) complexes have been studied. The three copper(II) compounds 2–4 show identical absorption spectra and redox properties when measured in acetonitrile, although in nitromethane they show small but definite differences in their spectral and redox features.     

Syntheses,supramolecular structures and properties of six coordination complexes based on 5-sulfosalicylic acid and bipyridyl-like chelates

Six new complexes constructed by 5-sulfosalicylic acid and bipyridyl-like ligands (2,2′-bipy and 1,10-phen), namely [Cu₄(OH)₂(ssal)₂(phen)₄ · 7H₂O] (1), [Cu₄(OH)₂(ssal)₂(bipy)₄ · 2H₂O] (2), [Cd(Hssal)(bipy)] (3), [Cd(HL)₂(phen)₂] (4), [Cr(ssal)(bipy)(H₂O)₂ · 2H₂O] (5) and [Cr(ssal)(phen)₂] (6) (H₃ssal = 5-sulfosalicylic acid, H₂L = p-hydroxybenzenesulfonic acid, bipy = 2,2′-bipy, phen = 1,10-phen) were prepared under hydrothermal conditions and their structures were determined by single-crystal X-ray diffraction. Complexes 1 and 2 are both tetranuclear copper complexes with a stepped topology. In complex 3, a new coordination mode of the Hssal²⁻ group is reported in this work. During the synthetic process of complex 4, in situ decarboxylation of 5-sulfosalicylic acid into p-hydroxybenzenesulfonic acid is involved. Two chromium 5-sulfosalicylates (5 and 6) are reported for the first time. These new complexes display different supramolecular structures by O–H?O, C–H?O hydrogen bonds as well as π?π, C–H?π and O?π interactions. The results of magnetic determination show that ferromagnetic interactions exist in complex 1, however, antiferromagnetic interactions exist in 2.     

Luminescent zinc and cadmium metal-organic frameworks based on tetrazole ligands

Three metal-organic frameworks with 1D zigzag chain [Zn(dte)(H₂O)₃]·2H₂O (1), 2D double layer [Cd(dtb)(H₂O)(phen)] (2), 3D network [Zn(dte)(phen)] (3) based on tetrazole-based ligands (H₂dtb = 1,3-dis(2H-tetrazol-5-yl)benzene, H₂dte = 1,4-ditetrazolylethylene, phen = 1,10-phenanthroline), have been synthesized and characterized. All the compounds exhibit unusual strong luminescence at room temperature in the solid state and can be potentially used as luminescent materials.