Synthesis,spectroscopic characterization,and crystal structures of copper(I) iodide clusters of N-methylthiourea and 1,3-diazinane-2-thione

Two copper(I) iodide complexes, [Cu₄(Metu)₆I₄] (I) and [Cu₈(Diaz)₁₂I₈] (II) (Metu = N-methylthiourea; Diaz = 1,3-diazinane-2-thione), have been prepared and their structures been determined by X-ray crystallography. The crystal structures show that complex I is a tetranuclear, while II is an octanuclear cluster, both having a Cu : S ratio of 2 : 3, characteristic of metallothioneins. In I, each of the four copper atoms is coordinated to three thiourea ligands and one iodide ion in a distorted tetrahedral mode adopting admantane-like structure. In II, four types of core arrangements are observed around copper(I), which include, Cu(μ-S₂)I₂, Cu(μ-S₂)(μ-I)I, Cu(μ-S₃)I, and Cu(μ-S₃)S each having copper(I) tetrahedrally coordinated. The complexes were also characterized by IR and ¹H and ¹³C NMR spectroscopy.     

Synthesis, spectroscopic, and thermal investigation of transition and non-transition complexes of metformin as potential insulin-mimetic agents

Complexes of [Mn(MF)₂(Cl)₂]·2H₂O (1), [Fe(MF)₂(Cl)₂]Cl·4H₂O (2), [Ni(MF·HCl)₂(Cl)₂]·6H₂O (3), [Cu(MF·HCl)₂(Cl)₂] (4), [Zn(MF·HCl)₂](NO₃)₂·6H₂O (5), [Cd₂(MF·HCl)(Cl)₄(H₂O)] (6), [Mg(MF·HCl)₂(Cl)₂]·6H₂O (7), [Sr₂(MF·HCl)(Cl)₄(H₂O)] (8), [Ba(MF·HCl)₂(Cl)₂]·2H₂O (9), [Pt(MF)₄] (10), [Au(MF)₃]Cl₃ (11), and [Pd(MF)₂]Cl₂ (12) were synthesized from Legitional behavior of metformin drug as a diabetic agent. The authenticity of the transition and non-transition metal complexes were characterized by elemental analyses, molar conductivity, (infrared, UV–Vis) spectra, effective magnetic moment in Bohr magnetons, electron spin resonance, thermal analysis, X-ray powder diffraction as well as scanning electron microscopy. Infrared spectral studies as well as elemental analyses revealed the existence of metformin in the base or hydrochloride salt forms in the chelation state acts as a bidentate ligand while the platinum(IV) complex is coordinated through the deprotonation of –NH group. The magnetic and electronic spectra of Mn(II), Fe(III), Ni(II), and Cu(II) complexes suggest an octahedral geometry. Antimicrobial screening of metformin and its complexes were determined against the (G⁺ and G^?) bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and fungi (Aspergillus flavus and Candida albicans).     

Thermal behaviour and characterisation of new biologically active Cu(II) complexes with benzimidazole as main ligand

Four coordination compounds of copper(II) were synthesised and characterised in solid state by elemental analysis, infrared, electronic and EPR spectroscopy, as well as by thermal analysis (TG/DTA). The complexes were formulated on the basis of experimental data as: [Cu(BzIm)₂(H₂O)]·H₂O (1), [Cu₂(Acr)₄(HBzIm)₂] (2), [Cu(Acr)₂(HBzIm)₂] (3) and [Cu(Acr)₂(HBzIm)₂(H₂O)]·H₂O (4). IR data are in accordance with the unidentate nature of benzimidazole, in complexes (2), (3) and (4), and bridge bidentate nature of benzimidazole, in complex (1), while acrylato acts as uni- or bridge/chelate ligand. The electronic spectra display the characteristic pattern of square planar, square pyramidal, or octahedral stereochemistry, also confirmed by EPR spectra. Thermal decomposition evidenced several well-defined steps as dehydration of complexes (1) and (4), benzimidazole molecule releases for all complexes and acrylate decomposition in carbonate for complexes (3) and (4). In all four cases, the final residue after thermal treatment in air flow is copper(II) oxide, formed during the decomposition steps for complexes (3) and (4), and, respectively, after the oxidation of the metallic copper for complexes (1) and (2). Antimicrobial activities of the complexes have been determined by in vitro assays, against various Gram-negative and Gram-positive bacterial and fungal strains. Copper(II) complexes were also evaluated for their cytotoxicity on eukaryotic cells.     

Copper(II) template synthesis of a new N2S2-donor macrocycle incorporating a pendent pyridyl substituent

The synthesis of the new potentially pentadentate ligand, 2,2??-(2-methyl-2-(pyridin-2-yl)propane-1,3-diyl)bis(sulfanediyl)diethanamine (L ¹ ), containing two thioether sulfurs, two ?CNH₂ amines and a pyridyl nitrogen heteroatom is described. Reaction of L ¹ with copper(II) chloride and addition of hexafluorophosphate anion has led to isolation of the mixed anion complex Cu₂(L ¹ )₂Cl(PF₆)₃. The synthesis and X-ray structure of cobalt(III) species, [Co(L ¹ )Cl](PF₆)₂, is also reported. In situ reaction of L ¹ with copper(II) as a metal template in the presence of formaldehyde and the carbon acid nitroethane together with triethylamine (as base) led to macrocycle ring closure to yield [Cu(L ² )Cl]PF₆ (where L ²  = 6,13-dimethyl-6-nitro-13-(pyridin-2-yl)-1,11-dithia-4,8-diazacyclotetradecane) whose X-ray structure shows that the copper centre has a distorted square pyramidal coordination geometry being bound by both ?CNH₂ nitrogens and both sulfurs of L ² while the pyridyl nitrogen remains uncoordinated.     

Copper complexes of two isomeric NS2-macrocycles

Two isomeric NS₂-macrocycles incorporating a xylyl group at ortho (o -L) and meta (m -L) positions were employed and their copper complexes (1?C5) were prepared and structurally characterized. The copper(II) nitrate complexes [Cu(L)(NO₃)₂] (1: L = o -L, 2: L = m -L) for both ligands were isolated. In each case, the copper center is five-coordinated with a distorted square pyramidal geometry. Despite the overall geometrical similarity, 1 and 2 show the different ligand conformation due to the discriminated packing pattern. Reaction of o -L with copper(II) perchlorate afforded complex 3 containing two independent complex cations [Cu(o -L)(H₂O)(DMF)(ClO₄)]⁺ and [Cu(o -L)(H₂O)(DMF)]²⁺; the coordination geometry of the former is a distorted octahedron while the latter shows a distorted square pyramidal arrangement. In the reactions of copper(I) halides (I or Br), o -L gave a mononuclear complex [Cu(o-L)I] (4) with a distorted tetrahedral geometry, while m -L afforded a unique exodentate 2:1 (ligand-to-metal) complex [trans-Br₂Cu(m-L)₂] (5) adopting a trans-type square-planar arrangement.     

Synthesis, characterization, and thermal decomposition of new copper (II) complex compounds with chlorhexidine

Three new copper (II) complex compounds with chlorhexidine (CHX) as ligand have been prepared and characterized by elemental and thermogravimetrical analyses, molar conductances, infrared, and UV–Vis spectra. Chlorhexidine acts as neutral tetradentate NNNN donor, coordinating through the four imine nitrogen atoms. Based on the experimental data the following formulas have been proposed for the complex compounds: [Cu(CHX)](NO₃)₂ (1), [Cu₂(CHX)Br₂Cl₂]·4H₂O (2), and [Cu(CHX)Cl]Cl (3). Thermal decomposition evidenced dehydration (complex 2), anionic moieties release and the ligand cleavage with chlorobenzene moieties removal for all complexes. The final residue is in all cases copper oxide. Antibacterial and antifungal activities of the complexes have been determined in vitro, by the cup-plate agar diffusion method, against Escherichia coli, Staphyloccocus aureus, and Candida albicans. The complexes present an activity comparable to that of chlorhexidine, the most active being [Cu₂(CHX)Br₂Cl₂]·4H₂O.     

Comparative investigation of the copper(II) complexes of (R)-, (S)- and (R,S)-1-phenyl-N,N-bis(pyridine-3-ylmethyl)ethanamine along with the related complex of (R,S)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine. Synthetic, magnetic, and structural studies

The interaction of the enantiopure (R)- and (S)-1-phenyl-N,N-bis(pyridine-3- ylmethyl)ethanamine ligands, R-L ¹ and S-L ¹ , with copper(II) chloride followed by addition of hexafluorophosphate resulted in the isolation of the corresponding enantiomeric complexes [Cu(R-L ¹ )Cl](PF₆) (1), [Cu(S-L ¹ )Cl](PF₆) (2) and [Cu(S-L ¹ )Cl](PF₆)??0.5Et₂O (3), in which dimerization occurs through two long Cu??????Cl interactions, the ??-chloro bridges being thus strongly asymmetric. The organic ligand is bound to the metal centre via its N₃-donor dipyridylmethylamine fragment in a planar fashion, such that each copper centre is in a square planar environment (or distorted square pyramidal with a long axial bond length if the additional interaction is considered). When R,S-L ¹ was employed in a parallel synthesis, the similar racemic complex [Cu(R,S-L ¹ )Cl](PF₆)??0.5MeOH (4) was obtained, in which the L ¹ ligands in each dimeric unit have opposite hands. In contrast to the complexes of L ¹ , the reaction of Cu(II) chloride with the related ligand, (R)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine (R-L ² ), yielded the mononuclear complex [Cu(R,S-L ² )Cl₂] (5), displaying a distorted square pyramidal coordination geometry. The structure of this product along with its corresponding circular dichroism spectrum revealed that racemisation of the starting R-L ² ligand has occurred under the relatively mild (basic) conditions employed for the synthesis. A temperature-dependent magnetic studies of the complexes 1, 2 and 5 indicate that a week ferromagnetic interaction is operative in each dicopper core in 1 and 2 with 2J?=?1.2?cm^?1. On the other hand, a week antiferromagnetic intermolecular interaction is operative for 5.     

Synthesis,structures and properties of three copper complexes created via in situ ligand cross-coupling reactions

Three copper complexes {[Cu₂(L¹)₂]·I₃} _n (1), [Cu(L²)₂] (2), and [Cu₂I₂(L³)₂(MBI)₂] (3) (MBI = 2-mercaptobenzimidazole, L¹ = N-(benzothiazol-2-yl)acetamidine anion, L² = N-(thiazol-2-yl) acetamidine anion, L³ = 3-methyl-[1,2,4]thiadiazolo[4,5-a]benzimidazole) have been synthesized solvothermally by the reactions of CuI with 2-benzothiazolamine, 2-aminothiazole and 2-mercaptobenzimidazole (MBI), respectively, in acetonitrile. In situ C–N (or C–S) cross-coupling ligand reactions were observed in all three complexes, and hypothetical reaction mechanisms are proposed for the formation of the ligands and their complexes. The single-crystal X-ray structural analysis reveals that both the Cu(II) and Cu(I) atoms are located in pseudo-tetrahedral environments in complex 1, and L¹ acts as a double bidentate ligand which coordinates with the Cu(I) and Cu(II) atoms to form a 1D coordination polymer. Unlike complex 1, the Cu(II) atom in complex 2 is in a square planar geometry, coordinated by two L² ligands with relatively small steric hindrance. In complex 3, the Cu(I) atoms have a distorted tetrahedral geometry, being coordinated by one nitrogen atom from L³, two sulfur atoms of MBI ligands, and one iodide. The sulfur atoms from MBI ligands bridge two Cu(I) atoms to form a binuclear complex. All three complexes exhibit relatively high thermal stabilities. Complex 1 displays intense fluorescence emission at 382 nm and complex 3 displays two intense fluorescence emissions at 401 and 555 nm.     

Synthesis, crystal structures, and properties of inorganic-organic hybrid complexes constructed from copper(II) macrocyclic fragment

Reaction of a macrocyclic copper(II) complex [Cu(L)](ClO₄)₂ · 3H₂O (I) (L = 1,3,10,12,16,19-hexaazatetracyclotetracosane) with a hexapod carboxylate ligand H₆TTHA (H₆TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid) and a tripod carboxylate ligand H₃TATB (H₃TATB = 4,4′,4″-S-triazine-2,4,6-triyl-tribenzoic acid) yielded two mononuclear copper(II) complexes [Cu(L)][H₄TTHA] · 4H₂O (II) and [Cu(L)][HTATB] · 4H₂O (III). The complexes I–III have been structurally characterized. The crystal structures of complexes II and III show the copper(II) ion has a distorted pentacoordinate square-pyramidal geometry with two secondary and two tertiary amines from the macrocyclic complex [Cu(L)]²⁺ and one oxygen atom from the carboxylate ligand group at the axial position. The UV-Vis spectra are utilized to discuss the hydrolysis of the complex II.     

Synthesis, characterization and structures of copper(II) complexes containing carboxylate and sulfonate groups

Four copper(II) complexes containing Schiff base and reduced Schiff base ligands derived from pyridine-2-aldehyde and amino acid containing carboxylate and sulfonate functional groups (N-(2-pyridylmethylene)-amino acid and N-(2-pyridylmethyl)-amino acid, (amino acids = ??-alanine and aminoethanesulfonic acid) namely, [Cu(Pbals)(H₂O)₂]ClO₄·H₂O 1, [Cu(Pbal)(ClO₄)(H₂O)] 2, [Cu₂(Paes)₂(ClO₄)₂]·2H₂O 3, and [Cu(Pae)(H₂O)]·ClO₄·H₂O 4 have been synthesized and characterized. The structural features of carboxylate and sulfonate donor groups have been elucidated. These copper(II) complexes demonstrate different coordination behaviour of the carboxylate and sulfonate groups. Carboxylate groups in complexes 1 and 2 bridge the metal centers and facilitate the formation of 1D helical coordination polymeric structures. In compound 3, the sulfonate groups bridge the metal centers to form a discrete dinuclear complex. In 4, the sulfonate groups link the neighbouring metal centers to form a 1D coordination polymeric structure.     

Copper(II), iron(III) and cobalt(III) complexes of the pendent-arm cyclam derivative 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane

The interaction of Cu(II), Fe(III) and Co(III) with 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane (L ³ ) incorporating a pendent amine group has led to isolation of the new octahedral complexes [Cu(HL ³ )(ClO₄)₂]Cl·H₂O (1), [Fe(L ³ )Cl](S₂O₆)·H₂O (2), [Co(L ³ )Cl](ClO₄)_1.5Cl_0.5·0.25H₂O (3), [Co(HL ³ )Cl₂](ClO₄)₂·H₂O (4) and [Co(L ³ )Cl]₂(S₂O₄)(ClO₄)₂ (5). In (1) the copper ion occupies the macrocyclic cavity of protonated (–NH₃ ⁺) L ³ which is present in its trans-III configuration; weakly bound ClO₄ ^? ligands occupy the axial positions. The X-ray structure of (2) showed that Fe(III) occupies the N₄-macrocyclic cavity of L ³ in a trans-III configuration, with the pendent amine group binding in an axial position. The remaining axial position is occupied by a Cl^? ligand. Chromatography of the product obtained from the reaction of Na₃[Co(CO₃)₃] with L ³ yielded three fractions. Fraction 1 yielded crystals (3) composed of three crystallographically independent species incorporating cations of type [Co(L ³ )Cl]²⁺ with very similar structures; in each case the macrocyclic ring nitrogens of L ³ are bound to the Co(III) in an asymmetric cis-fashion. Fraction 2 yielded the trans-III octahedral cationic complex (4) incorporating L ³ in its protonated form. The Co(III) complex (5) from fraction 3 shows a different coordination arrangement to the products from fractions 1 or 2. The macrocyclic ring coordinates in its trans-III form, but the axial sites in this case are occupied by the pendent-NH₂ group and a Cl^? ligand.     

Synthesis,crystal structure,and electronic structure of a copper(II) chloride complex with 9(E)-phenanthrene-9,10-dione[(1Z)-3,3-dimethyl-3,4-dihydroisoquinolin-1(2H)-ylidene]hydrazone [Cu2(L-H)2Cl2]

The [Cu₂(L-H)₂Cl₂] compound (I) has been obtained by the reaction of 9(E)-phenanthrene-9,10-dione[(1Z)-3,3-dimethyl-3,4-dihydroisoquinolin-1(2H)-ylidene]hydrazone with copper(II) chloride. The crystal and molecular structure of I has been determined by X-ray crystallography. The L-H anion acts as a tridentate chelating ligand and is coordinated to the Cu atom through the O(1) atoms of the phenanthrenequinone moiety, the N(1) atom of the dihydroisoquinoline moiety, and the N(3) atom of the azo group to form two five-membered chelate rings. Complex I is a dimer with a double chloride bridge. The coordination polyhedron of the Cu atom is completed to a distorted pyramid by two chlorine atoms. The molecular and electronic structures of the L molecule and the model [Cu(L-H)Cl] complex have been determined by the density functional theory method. Spectroscopic characteristics of I have been determined.     

Cyanide-bridged one-dimensional bimetallic complexes based on a tridentate copper(II) building block: synthesis,crystal structures and magnetic properties

The reactions of [M^III(CN)₆]^3? (M = Cr or Co) with Cu^II complexes of a tridentate schiff base [Cu(aemp)Cl] or [Cu(aemp)Ac]₂ (Haemp = 2-[(2-amino-ethylimino)-methyl]-phenol) give rise to 1D cyanide-bridged bimetallic coordination polymers [Cu₄(aemp)₄(H₂O)₂][Cr(CN)₆]Cl (1) and [Cu₃(aemp)₃(H₂O)][Co(CN)₆]·2H₂O·MeOH (2). In complex 1, the six cyanide ligands of the [Cr(CN)₆]^3? moiety are involved in bridging, while in complex 2 only five cyanide ligands act as bridges to give a neutral chain. Magnetic studies reveal that complex 1 exhibits intermetallic ferromagnetic coupling, with J = 8.2 cm^?1.     

Copper(II) malonate coordination frameworks with amino-1,2,4-triazole: Crystal structures and magnetic properties of [Cu2(mal)2(datz)2(H2O)]·5H2O and [Cu2(mal)2(atz)2(H2O)]·3H2O

Two new malonato-bridged copper(II) complexes of the composition [Cu₂(mal)₂(datz)₂(H₂O)]·5H₂O (1) and [Cu₂(mal)₂(atz)₂(H₂O)]·3H₂O (2) (mal = malonate, atz = 4-amino-1,2,4-triazole, datz = 3,5-diamino-1,2,4-triazole) are prepared and characterized by X-ray crystal structure determination and magnetic studies. The environment of each copper atom in 1 and 2 has distorted square pyramidal and octahedral geometries. The intrachain copper-copper separation is 6.305 Å and 3.640 Å across the carboxylates and trizolates bridges respectively for complexes 1 and 2. The magnetic properties of 1 and 2 are investigated in the temperature range 2–300 K. The overall antiferromagnetic behavior is observed in both cases.     

Syntheses, structures, and properties of the Co(II), Ni(II), and Cu(II) complexes with 5-carboxy- and 5-methoxycarbonylpyrazoles

New cobalt(II), nickel(II), and copper(II) complexes based on 5-methoxycarbonyl-3-me-thylpyrazole (MePzCOOMe), [Co(MePzCOOMe)₂(H₂O)₂](NO₃)₂ (I), [Ni(MePzCOOMe)₂(H₂O)₂] (NO₃)₂ (II), and [Cu(MePzCOO)₂(H₂O)] · 3H₂O (III), were synthesized. The compounds were studied by X-ray diffraction analysis, IR spectroscopy, and static magnetic susceptibility. The molecular and crystal structures of complexes I and III were determined by X-ray structure analysis.     

A supramolecular copper(II) compound with double bridging water ligands: synthesis, crystal structure, spectroscopy, thermal analysis, and magnetism

A complex of composition {[{Cu(NDC)(OH₂)(tn)(μ-OH₂)}₂]·2H₂O}_∞ (1) and a mononuclear complex salt [Cu(OH₂)₂(tn)₂](NDC)·3H₂O (2), where NDC = 2,6-naphthalenedicarboxylate dianion and tn = 1,3-diaminopropane, were simultaneously crystallized from an aqueous solution of the copper(II) naphthalenedicarboxylate—1,3-diaminopropane—methanol system. The crystal and molecular structures of both complexes were determined by single-crystal X-ray diffraction. Compound (1) consists of a supramolecular coordination complex in which the monomeric unit is assembled from a homodinuclear Cu(II) bridged by two water ligands. The Cu(II) centers exhibit distorted octahedral coordination; the equatorial plane is provided by one chelating tn ligand, one NDC^2? ligand, one μ-H₂O while the axial positions are occupied by H₂O and μ-H₂O. Strong intra- and/or intermolecular hydrogen bonds, also involving the crystallization water molecules, together with π–π stacking interactions, are involved in building up the supramolecule. The solid structure of compound (2) includes three water molecules of crystallization, the counter ion NDC^2?, and a Cu(II) cationic complex in which the metal is six-coordinated in an axially elongated octahedron defined by two chelating tn ligands in the equatorial plane and two water ligands in the axial positions. Thermal analyses of (1) show two significant weight losses corresponding to water molecules (lattice and coordinated), followed by the decomposition of the network.     

Chiral copper-bipyridine complexes: Synthesis, characterization and mechanistic studies on asymmetric cyclopropanation

Chiral bipyridine ligands of different steric properties when reacted with CuCl₂ formed orange, yellow or green solids of new copper(II) complexes, [Cu(L)Cl₂] (L = L2-6), in good yield. Together with [Cu(L1)Cl₂], these complexes were characterized in solution by UV-Vis spectroscopy and cyclic voltammetry. The complexes give d-d transitions between 860 and 970 nm, and exhibit one quasi-reversible Cu(II)/Cu(I) couple between +0.405 V and +0.516 V versus NHE. Two of the copper(II) complexes, [Cu(L5)Cl₂] and [Cu(L6)Cl₂], and a copper(I) complex of L1, [Cu(L1)Cl], were characterized by X-ray crystallography. The triflate derivatives of both the Cu(I) and Cu(II) complexes are active catalysts towards the cyclopropanation of ethyl diazoacetate with styrene. The asymmetric induction suffers when the size difference between the alkyl and alkoxyl groups was minimized. The mechanism of the cyclopropanation was studied with kinetic and competition experiments. The rate is first order in catalyst and ethyl diazoacetate, inverse order with styrene and is strongly affected by the counterion.     

Zero-, one- and two-dimensional bis-triazole-bis-amide-based copper(II) complexes tuned by polycarboxylates with different protonation degrees: assembly, structures and properties

Three bis-triazole-bis-amide-based copper(II) complexes with different dimensionality, [Cu(dtcd)₂ (1,3-HBDC)₂]·2H₂O (1), [Cu(dtcd) (1,3,5-H₂BTC)₂]·2H₂O (2) and [Cu₄(μ ₃-OH)₂(dtcd)₂(SIP)₂]·4H₂O (3) (dtcd = N,N′-di(4H-1,2,4-triazole) cyclohexane-1,4-dicarboxamide, 1,3-H₂BDC = 1,3-benzenedicarboxylic acid, 1,3,5-H₃BTC = 1,3,5-benzenetricarboxylic acid, NaH₂SIP = sodium 5-sulfoisophthalate), have been synthesized under different pH values and structurally characterized. Complex 1 exhibits a zero-dimensional mononuclear structure with one carboxyl group of 1,3-HBDC coordinating to copper(II), while the other carboxyl group is protonated. In complex 2, the Cu^II ions are bridged by the dtcd ligands forming a one-dimensional chain, in which only one carboxyl group of 1,3,5-H₂BTC coordinates with the metal, while the others are protonated. Complex 3 possesses a two-dimensional network based on tetranuclear Cu₄ clusters supported by the dtcd and nonprotonated SIP ligands. The various structures clearly indicate that the pH and polycarboxylates have a great influence on the dimensionality and structures of 1–3. The luminescence properties of 1–3 and magnetic properties of 3 were investigated.     

Synthesis,characterization and crystal structure determination of mononuclear and dinuclear copper(II) carboxylates: [Cu(Hdpa)2(en)] and [{Cu2(μ-na)4(CH3OH)2}·2CH3OH]

Two new copper complexes [Cu(Hdpa)₂(en)] (1) and [{Cu₂(μ-na)₄(CH₃OH)₂}·2CH₃OH] (2) (where en is ethylene diamine, Hdpa is 2′-carboxy-[1,10-biphenyl]-2-carboxylate anion and na is 1-naphtalenecarboxylate) have been synthesized and their crystal structures were determined by X-ray crystallography. Complex 1 was prepared from the reaction of Cu(NO₃)₂·3H₂O with ethylene diamine and 2,2′-biphenyldicarboxylic acid in a mixture of water and methanol and complex 2 was prepared from the reaction of CuSO₄·5H₂O with 1-naphtalenecarboxylic acid in methanol. The two complexes were characterized by IR, UV–vis, luminescence and elemental analysis. Moreover, complex 2 was characterized by EPR spectroscopy and thermogravimetric analysis. Complex 1 is a monomer and complex 2 is a dimer with a paddle-wheel structure; both structures are without precedent in the literature.     

Copper(II) complexes of tetradentate N2S2 donor sets: Synthesis,crystal structure characterization and reactivity

Two mononuclear and one dinuclear copper(II) complexes, containing neutral tetradentate NSSN type ligands, of formulation [Cu^II(L¹)Cl]ClO₄ (1), [Cu^II(L²)Cl]ClO₄ (2) and [Cu^II₂(L³)₂Cl₂](ClO₄)₂ (3) were synthesized and isolated in pure form [where L¹ = 1,2-bis(2-pyridylmethylthio)ethane, L² = 1,3-bis(2-pyridylmethylthio)propane and L³ = 1,4-bis(2-pyridylmethylthio)butane]. All these green colored copper(II) complexes were characterized by physicochemical and spectroscopic methods. The dinuclear copper(II) complex 3 changed to a colorless dinuclear copper(I) species of formula [Cu^I₂(L³)₂](ClO₄)₂,0.5H₂O (4) in dimethylformamide even in the presence of air at ambient temperature, while complexes 1 and 2 showed no change under similar conditions. The solid-state structures of complexes 1, 2 and 4 were established by X-ray crystallography. The geometry about the copper in complexes 1 and 2 is trigonal bipyramidal whereas the coordination environment about the copper(I) in dinuclear complex 4 is distorted tetrahedral.