Synthesis,structural characterization,antimicrobial, DNA-binding,and photo-induced DNA cleavage activity of some bio-sensitive Schiff base copper(II) complexes

Schiff base mixed-ligand copper complexes [CuL¹(phen)Cl₂], [CuL¹(bipy)Cl₂], [Cu(L¹)₂Cl₂], [Cu(L²)₂Cl₂], [CuL²(bipy)Cl₂], and [CuL²(phen)Cl₂] (where L^1?=?4-[3,4-dimethoxy-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; L^2?=?4-[3-hydroxy-4-nitro-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; phen?=?1,10-phenanthroline; and bipy?=?2,2′-bipyridine) have been synthesized and characterized. Their DNA-binding properties have been studied by electronic absorption spectra, viscosity, and electrochemical measurements. The absorption spectral and viscosity results suggest that the copper(II) complexes bind to DNA via partial intercalation. The addition of DNA resulting in the decrease of the peak current of the copper(II) complexes indicates their interaction. Interaction between the complexes and DNA has also been investigated by submarine gel electrophoresis. The copper complexes cleave supercoiled pUC19 DNA to nicked and linear forms through hydroxyl radical and singlet oxygen in the presence of 3-mercaptopropionic acid as the reducing agent. These copper complexes promote the photocleavage of pUC19 DNA under irradiation at 360?nm. Mechanistic study reveals that singlet oxygen is likely to be the reactive species responsible for the cleavage of plasmid DNA by the synthesized complexes. The in vitro antimicrobial study indicates that the metal chelates have higher activity against the bacterial and fungal strains than the free ligands.     

Synthesis,characterization, and electrochemical study of two new macroacyclic Schiff bases and their copper(II) and zinc(II) complexes

Two new potentially octadentate N₂O₆ Schiff-base ligands 2-((E)-(2-(2-(2-((E)-2-hydroxy-3-methoxybenzylideneamino)phenoxy)phenoxy)phenylimino)methyl)-6-methoxyphenol H₂L¹ and 2-((E)-(2-(2-(2-((E)-2-hydroxy-3-methoxybenzylideneamino)phenoxy)-4-tert-butylphenoxy)phenylimino)methyl)-6-methoxyphenol H₂L² were prepared from the reaction of O-Vaniline with 1,2-bis(2′-aminophenoxy)benzene or 1,2-bis(2′-aminophenoxy)-4-t-butylbenzene, respectively. Reactions of H₂L¹ and H₂L² with copper(II) and zinc(II) salts in methanol in the presence of N(Et)₃ gave neutral [CuL¹]?·?0.5CH₂Cl₂, [CuL²], [ZnL¹]?·?0.5CH₂Cl₂, and [ZnL²] complexes. The complexes were characterized by IR spectra, elemental analysis, magnetic susceptibility, ESI–MS spectra, molar conductance (Λ_m), UV-Vis spectra and, in the case of [ZnL¹]?·?0.5CH₂Cl₂ and [ZnL²], with ¹H- and ¹³C-NMR. The crystal structure of [ZnL¹]?·?0.5CH₂Cl₂ has also been determined showing the metal ion in a highly distorted trigonal bipyramidal geometry. The electrochemical behavior of H₂L² and its Cu(II) complex, [CuL²], was studied and the formation constant of [CuL²] was evaluated using cyclic voltammetry. The logarithm value of formation constant of [CuL²] is 21.9.     

Challenges in Modelling and Optimization of Stability Constants in the Study of Metal Complexes with Monoprotonated Ligands. Part II

The influence of 2‐hydroxy‐3‐[(2‐hydroxy‐1,1‐dimethylethyl)amino]propane‐1‐sulfonic acid (AMPSO=HL) on systems containing copper(II) was studied by glass‐electrode potentiometry (GEP) and direct‐current polarography (DCP), at fixed total‐ligand‐to‐total‐metal‐concentration ratios and various pH values (25°, 0.1M KNO₃ medium). The predicted model ([CuL]⁺, [CuL(OH)], [CuL₂], [CuL₂(OH)]^?, [CuL₂(OH)₂]^2?, and [CuL₃]^?) and the overall stability constants for species found were obtained by combining results from both electrochemical techniques. The last five complexes are reported for the first time. For the species [CuL]⁺, [CuL₂], [CuL₃]^?, and [CuL₂(OH)₂]^2?, it was possible to determine stability constants with reasonable certainty and their values, as log β, were found to be 4.62±0.04, 9.5±0.1, 13.4±0.1, and 21.2±0.1, respectively. For the species [CuL(OH)] and [CuL₂(OH)]^?, stability constants 11.7±0.2 and 15.6±0.2, respectively, are presented as indicative values. It was demonstrated that AMPSO buffer may decrease the Cu²⁺ concentration by ten orders of magnitude by forming complexes with Cu²⁺. For the first time, the correction in DCP waves for the adsorption of the ligand and quasi‐reversibility of the metal allowed to determine stability‐constant values that are in good agreement with the values obtained by GEP. The importance of graphic analysis of data and significance of employing two analytical techniques was demonstrated; neither GEP nor DCP would be able to provide the correct M/L/OH^? model and reliable stability constants when used independently.     

Ruthenium(II) ligated to tetradentate diaminodithioethers: synthesis,characterisation and electrochemistry

Ruthenium(II) complexes containing two tetradentate ligands, 1,2-bis(o-aminophenylthio)ethane (L¹) and 1,2-(oaminophenylthio)xylene (L²), have been prepared. The complexes, which are of the type Ru(L)Cl₂ [L = L¹ (1);/L² (2)], [Ru(L)(PPh₃)Cl]Cl [L = L¹ (3); L² (4)] and [Ru(L)(bpy)](PF₆)₂ [L = L¹ (5);/L² (6)], were characterised by elemental analysis, i.r., u.v.-vis. and n.m.r. spectroscopy and their electrochemical behaviour has been examined by cyclic voltammetry using a glassy carbon working electrode and an Ag/AgCl electrode as the reference electrode. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis,characterization, and X-ray crystal structures of metal complexes with new Schiff-base ligands and their antibacterial activities

Two new potentially hexadentate Schiff bases, [H₂L¹] and [H₂L²], were prepared by condensation of 2-(3-(2-aminophenoxy)naphthalen-2-yloxy)benzenamine with 3,5-di-tert-butyl-2-hydroxy benzaldehyde and o-vanillin, respectively. Reaction of these ligands with cobalt(II) chloride, copper(II) perchlorate, and zinc(II) nitrate gave complexes ML. The ligands and their complexes have been characterized by a variety of physico-chemical techniques. The solid and solution state investigations show that the complexes are neutral. Molecular structures of [CuL¹], [CoL¹]?·?C₇H₈, and [ZnL²]?·?CH₃CN, which have been determined by single-crystal X-ray diffraction, indicate that [CuL¹] and [ZnL²]?·?CH₃CN display distorted square planar and distorted trigonal-bipyramidal geometry, respectively; the geometry around cobalt in [CoL¹]?·?C₇H₈ is almost exactly between trigonal bipyramidal and square pyramidal. The synthesized ligands and their complexes were screened for their antibacterial activities against eight bacterial strains and the ligands and complexes have antibacterial effects. The most effective ones are [CuL²] against Proteus vulgaris, Serratia marcescens, Staphylococcus subtilis, [H²L¹] against S. subtilis, and [H₂L²] against S. subtilis.     

Ni(II) and Cu(II) complexes of new unsymmetrical N2O2 Schiff bases derived from 3-(2-aminobenzylimino)-1-phenylbutan-1-ol: synthesis,structure, antibacterial properties,and electrochemistry

Two new N₂O₂ unsymmetrical Schiff bases, H₂L¹ = 3-[({o-[(E)-(o-hydroxyphenyl)methylideneamino]phenyl}methyl)imino]-1-phenyl-1-buten-1-ol and H₂L² = 3-[({o-[(E)-(2-hydroxy-1-naphthyl)methylideneamino]phenyl}methyl)imino]-1-phenyl-1-buten-1-ol, and their copper(II) and nickel(II) complexes, [CuL¹] (1), [CuL²] (2), [NiL¹] (3), and [NiL²] (4), have been synthesized and characterized by elemental analyses and spectroscopic methods. The crystal structures of these complexes have been determined by X-ray diffraction. The coordination geometry around Cu(II) and Ni(II) centers is described as distorted square planar in all complexes with the CuN₂O₂ coordination more distorted than the Ni ones. The electrochemical studies of these complexes indicate a good correlation between the structural distortion and the redox potentials of the metal centers. The ligand and metal complexes were also screened for their in vitro antibacterial activity.     

Crystal structures and in vitro anticancer studies on new unsymmetrical copper(II) Schiff base complexes derived from meso-1,2-diphenyl-1,2-ethylenediamine: a comparison with related symmetrical ones

Two new unsymmetrical copper(II) Schiff base complexes, [CuLⁿ(py)]ClO₄ (n = 1, 2) in which Lⁿ represents a tridentate N₂O type Schiff base ligand, were synthesized. Lⁿs were derived from monocondensation of meso-1,2-diphenyl-1,2-ethylenediamine with salicylaldehyde or 3-methoxysalicylaldehyde. The reaction between [CuLⁿ(py)]ClO₄ and other salicylaldehyde derivatives resulted in new N₂O₂ unsymmetrical tetradentate Cu^II complexes, CuL^3–6. Crystal structures of [CuL¹(py)]ClO₄, CuL⁴, and CuL⁵ were obtained. These new complexes as well as a series of related symmetrical ones (i.e. CuL^7–12) were tested for their in vitro anticancer activity against human liver cancer cell line (Hep-G2) by MTT and apoptosis assay. All of the complexes showed considerable cytotoxic activity against tumor cell lines (IC₅₀ = 5.13–16.24 μg mL^?1). The symmetrical CuL⁷ was the most potent anticancer derivative (IC₅₀ = 5.13 μg mL^?1) compared to the control drug 5-FU (IC₅₀ = 5.4 μg mL^-1, p < 0.05). Flow cytometry experiments showed that the copper derivatives especially [CuL²(py)]ClO₄ and CuL⁷ induced more apoptosis on Hep-G2 tumor cell lines compared to 5-FU.     

Transition Metal Complexes with Pyrazole-based Ligands. Part 8. Characterization and thermal decomposition of zinc(II) complexes with di- and trisubstituted pyrazoles

We report the synthesis and the characterization (elemental analysis, FT-IR spectroscopy, thermal methods and molar conductivity measurements) of the mixed complexes of zinc with acetate and 3-amino-5-methylpyrazole, HL ¹, [Zn(OAc)₂(HL¹)₂], or 3-amino-5-phenylpyrazole, HL ² [Zn(OAc)₂(HL²)₂], or 4-acetyl-3-amino-5-methylpyrazole, HL ³, [Zn(OAc)(L³)(HL³)]₂, with isothiocyanate and HL ² [Zn(SCN)₂(HL²)₂], or HL ³ [Zn(SCN)₂(HL³)₂], and with nitrate, isothiocyanate and 3,5-dimethyl-1-carboxamidinepyrazole, HL ⁴ [Zn(NO₃)(NCS)(HL⁴)₂]. The thermal decomposition of the complexes is generally continuous resulting zinc oxide as end product,except [Zn(OAc)(L³)(HL³)]₂ in which case a well-defined intermediate was observed between 570–620 K. On the basis of the IR spectra and elemental analysis data of the intermediate a decomposition scheme is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Altering the Activity of Catechol Oxidase Model Compounds by Electronic Influence on the Copper Core

The catecholase activity of the dicopper(II) complexes [Cu₂(L¹)(μ‐OCH₃)(NCCH₃)₂](PF₆)₂·H₂O·CH₃CN ( 1 ), [Cu₂(L²)(μ‐OH)(MeOH)(NCCH₃)](BF₄)₂ ( 2 ), [Cu₂(L³)(μ‐OMe)(NCCH₃)₂](BF₄)₂·2CH₃CN·H₂O ( 3 ), [Cu₂(L²)(μ‐OAc)₂]BF₄·H₂O ( 4 ), [Cu₂(L⁴)(μ‐OAc)₂]ClO₄ ( 5 ) and [Cu₂(L⁵)(μ‐OMe)(NCCH₃)₃(OH₂)](ClO₄)₂·2CH₃OH·CH₃CN ( 6 ) consisting of varying para‐substituted phenol ligands HL¹ = 4‐trifluoromethyl‐2,6‐bis((4‐methylpiperazin‐1‐yl)methyl)phenol, HL² = 4‐bromo‐2,6‐bis((4‐methyl‐1,4‐diazepan‐1‐yl)methyl)phenol, HL³ = 4‐bromo‐2‐((4‐methyl‐1,4‐diazepan‐1‐yl)methyl)‐6‐((4‐methylpiperazin‐1‐yl)methyl)phenol, HL⁴ = 2,6‐bis((4‐methylpiperazin‐1‐yl)methyl)‐4‐nitrophenol and HL⁵ = 4‐tert‐butyl‐2,6‐bis((4‐methylpiperazin‐1‐yl)methyl)phenol was studied. The main difference within the six complexes lies in the individual copper–copper separation that is enforced by the chelating side arms of the phenolate ligand entity and more importantly in the exogenous bridging solvent, hydroxide, methanolate or acetate ions. The distance between the copper cores varies from 2.94Å in 1 to 3.29Å in 5 . The catalytic activity of the complexes 1 – 6 towards the oxidation of 3,5‐di‐tert‐butylcatechol was determined spectrophotometrically by monitoring the increase of the 3,5–di‐tert‐butylquinone characteristic absorption band at about 400 nm over time saturated with O₂. The complexes are able to oxidize the substrate 3,5‐di‐tert‐butylcatechol to the corresponding o‐quinone with distinct catalytic activity (k_cat between 92 h^?1 and 189 h^?1), with an order of decreasing activity 6 > 5 > 1 , 2 , 4 ≥ 3 . A kinetic treatment of the data based on the Michaelis‐Menten approach was applied. A correlation of the catecholase activities with the variation of the para‐ substituents as well as other effects resulting from the copper core distances is discussed. [Cu₂(L⁵)(μ‐OMe)(NCCH₃)₃(OH)₂](ClO₄)₂·2CH₃OH·CH₃CN ( 6 ) exhibited the highest activity of the six complexes as a result of its high turnover rate.     

Synthesis,characterization and ascorbic acid oxidase mimetic catalytic activity of copper(II) picolyl hydrazone complexes

Four new picolyl hydrazones were prepared via Schiff-base condensation of picolonic acid hydrazide with α-formyl-(L¹), α-acetyl-(L²), α-benzoyl-(L³) pyridine and α-formyl-(L⁴) thiophene. Copper(II) complexes of these hydrazones and a series of copper(II) complexes containing (L²) and various anions (Cl, Br, NO₃, SCN, SO₄, ClO₄, AcO, PF₆ and BF₄) have been synthesized. Elemental, thermal analysis, molar conductivity, magnetic moment measurements and spectral (i.r., electronic and e.s.r.) studies have been used to characterize the prepared compounds. The overall structure and reactivity of the reported copper(II) chelates critically depend on the ligand structure and the nature of counter anion incorporated in the complex molecule. Octahedral [complex (7)], square-pyramidal [complex (8)] and square-planar monomeric species [complexes (1–6), (9) and (10)] and a dimeric structure with oxygen bridge in square-planar geometry [complexes (11) and (12)] were suggested. The reported copper(II) complexes exhibit promising oxidase catalytic activity towards the aerobic oxidation of vitamin C. A linear correlation exists between the oxidase catalytic activity and the Lewis-acidity of the central copper(II) ion created by the donating properties of the parent ligand, as well the irregularity of the coordination environment. The probable mechanistic implications of the catalytic oxidation reactions are discussed.     

Synthesis and characterization of copper(II) and cobalt(II) complexes with two new potentially hexadentate Schiff base ligands. X-ray crystal structure determination of one copper(II) complex

Two new potentially hexadentate N₂O₄ Schiff base ligands 2-((z)-(2-(2-(2-((z)-3,5-di-tert-butyl-2-hydroxybenzylideneamino) phenoxy) phenoxy) phenylimino) methyl)-4,6-di-tert-butylphenol [H₂L¹] and 2-((z)-(2-(2-(2-((z)-3,5-di-tert-butyl-2-hydroxybenzylideneamino) phenoxy)-5-tert-butylphenoxy) phenylimino) methyl)-4,6-di-tert-butylphenol [H₂L²] were prepared from the reaction of 3,5-di-tert-butyl-2-hydroxy benzaldehyde with 1,2-bis(2′-aminophenoxy)benzene or 1,2-bis(2′-aminophenoxy)-4-t-butylbenzene, respectively. From the direct reaction of ligands [H₂L¹] and [H₂L²] with copper(II) and cobalt(II) salts in methanolic solution and in the presence of N(Et)₃ the neutral [CuL¹], [CuL²], [CoL¹] and [CoL²] complexes were prepared. All complexes were characterized by IR spectra, elemental analysis, magnetic susceptibility, mass spectra, molar conductance (Λ_m), UV-Vis spectra and in the case of [CuL²] with X-ray diffraction. X-ray crystal structure of [CuL²] showed that the complex contains copper(II) in a distorted square planar environment of N₂O₂ donors. Three CH/π interactions were observed in the molecular structure of latter complex.     

Synthesis,DNA-binding and cleavage studies of macrocyclic copper(II) complexes

Two macrocyclic copper(II) complexes, [CuL¹](ClO₄)₂ (L¹ = 2,6,9,13-tetraparacyclophane, a Schiff base) and [CuL²]Cl₂ [L² = 3,10-bis(2-benzyl)-1,3,5,8,10,13-hexaazacyclotetradecane] have been prepared and characterized by elemental analysis, u.v.–vis., i.r. and mass spectra. Absorption, fluorescence, circular dichroic spectra and viscosity experiments have been carried out on the interaction of the two complexes with calf thymus CT DNA. The results suggest that both complexes can bind to CT DNA by intercalation via the aromatic moiety ring in the macrocycle into the base pairs of DNA. [CuL¹](ClO₄)₂ binds to CT DNA more strongly than [CuL²]Cl₂. The position of the aromatic ring in the macrocycle plays an important role in deciding the extent of binding of the complexes to DNA. Significantly, the complexes have been found to be single-strand DNA cleavers in the presence of H₂O₂ or/and 2-mercaptoethanol.     

Synthesis,characterization, and antitumor activities of two copper(II) complexes with pyrazole derivatives

Two mononuclear copper(II) complexes with pyrazole derivatives, 1,1′-(anthracen-9-ylmethylene)bis(1H-pyrazole) (L¹ ) and 9-(4-(di(1H-pyrazol-1-yl)methyl)phenyl)-9H-carbazole (L² ), of formulae [CuL¹(CH₃CN)₂](ClO₄)₂ (1) and [CuL²(CH₃CN)₂](ClO₄)₂ (2) were prepared. Both complexes were confirmed by IR, MS, ¹H NMR, and elemental analyses. Complex 1 was also characterized by X-ray crystallography, confirming that copper(II) is coordinated by four nitrogen atoms from two L¹ and two oxygen atoms from two perchlorates. Furthermore, all ligands and complexes were tested in vitro for their antitumor activities using mouse melanoma cell line B16-F10, HepG2 human hepatoma cell line, and A549 human lung adenocarcinoma cell line. Both complexes displayed potent cytotoxicity and are promising substrates for further investigations.     

A cyclic voltammetric study of iron(II)/ruthenium(II) complexes with bis(tertiary phosphines)

Summary Nine complexes of Fe^IIRu^II with bis(tertiary phosphines), namely, 1,2-bis(diphenylphosphino)ethane (dppe), 1,2-bis (diphenylphosphino)ethylene (dppen) and o-phenylenebis (diphenylphosphine) (o-diphos) were studied using cyclic voltammetry. The half-wave potentials for the complexes studied are: (1) [FeCl₂(dppe)], 0.050V; (2) [Fe(NCS)₂(dppe)₂], 0.265V; (3) [RuCl₂(dppe)₂], 0.548V; (4) [FeCl₂(dppen)₂], 0.225V; (5) [Fe(NCS)₂-(dppen)₂], 0.290V; (6) [RuCl₂(dppen)₂], 0.690V; (7) [FeCl₂(o-diphos)₂] 0.160V; (8) [Fe(NCS)₂(o-diphos)₂] 0.582V; and (9) [RuCl₂(o-diphos)₂], 0.265V. The redox potentials are related to the nature of the ligand, the nature of the metal, the stereochemistry of the complex and the ligand field strength.     

Syntheses,Structures, and Biological Activity of NiII,PdII, and PtII Complexes with New Tetradentate Benzamidine Ligands

N‐(Dialkylthiocarbamoyl)benzimidoyl chlorides react with o‐(salicylidenimine)benzylamine with formation of a novel class of tetradentate benzamidine ligands (H₂L^Et and H₂L^Morph), which readily react with Ni(CH₃COO)₂, [PdCl₂(CH₃CN)₂], and [PtCl₂(PPh₃)₂] under formation of complexes of the composition [M(L^R)] [M = Ni ( 4 ), Pd ( 5 ), Pt ( 6 )]. In all complexes, H₂L^R is doubly deprotonated and bonded to the metal ion via its N₂OS donor set and establishes a distorted square‐planar coordination sphere. The antiproliferative effects of the compounds on MCF‐7 and Hep‐G2 cells were studied. The complexes of H₂L^Morph are generally more active than those of H₂L^Et. While H₂L^Et and its complexes exhibit stronger effects on the Hep‐G2 line, the corresponding compounds of H₂L^Morph show almost equal effects on the two cell lines. In each series of compounds, the cytotoxicity increases in the order H₂L^R << 4 < 5 < 6 .     

Synthesis and spectral studies of new N2S2 and N2O2 Mannich base ligands and their metal complexes

New Mannich bases bis(thiosemicarbazide methyl) phosphinic acid H₃L¹ and bis(1-phenylsemicarbazide methyl) phosphinic acid H₃L² were synthesized from condensation of phosphinic acid and formaldehyde with thiosemicarbazide and 1-phenylsemicarbazide, respectively. Monomeric complexes of these ligands, of general formula K₂[Cr^III(L ⁿ )Cl₂], K₃[Fe^II(L¹)Cl₂], K₃[Mn^II(L²)Cl₂], and K[M(L ⁿ )] (M = Co(II), Ni(II), Cu(II), Zn(II) or Cd(II); n = 1, 2) are reported. The mode of bonding and overall geometry of the complexes were determined through IR, UV-Vis, NMR, and mass spectral studies, magnetic moment measurements, elemental analysis, metal content, and conductance. These studies revealed octahedral geometries for the Cr(III), Mn(II), and Fe(II) complexes, square planar for Co(II), Ni(II), and Cu(II) complexes and tetrahedral for the Zn(II) and Cd(II) complexes. Complex formation via molar ratio in DMF solution has been investigated and results were consistent to those found in the solid complexes with a ratio of (M : L) as (1 : 1).     

Biocidal and catalytic efficiency of ruthenium(III) complexes with tridentate Schiff base ligands

The reaction of the Schiff bases (obtained by condensing isatin with o‐aminophenol/o‐aminothiophenol/o‐aminobenzoic acid) with [RuX₃(EPh₃)₃] (where X = Cl/Br; E = P/As) in benzene afforded new, air‐stable Ru(III) complexes of the general formula [Ru(L)X(EPh₃)₂] (L = dianion of tridentate Schiff bases). In all these reactions, the Schiff base ligand replaces one triphenylphosphine/triphenylarsine and two chlorides/bromides from the ruthenium precursors. The complexes were characterized by elemental analyses, spectral (FT–IR, UV–vis, ¹H and ¹³C NMR for the ligands, and EPR) and electrochemical studies. All the metal complexes exhibit characteristic LMCT absorption bands in the visible region. The catalytic reactivity proved these complexes to be efficient catalysts in the oxidation of alcohols and C? C coupling. All the complexes were screened for their biocidal efficiency against bacteria such as Staphylococcus epidermidis and Escherichia coli and fungi such as Botrytis cinerea and Aspergillus niger at 0.25, 0.50 and 1% concentrations. Copyright © 2010 John Wiley & Sons, Ltd.     

Structure of the Cu(II) chloride complex with 4-amino-l,2,4-triazole Cu(C2H4N4)Cl2

The coordination compounds of copper(II) chloride and bromide with 1,2,4-triazole (L¹) and 4-amino1,2,4-triazole (L²), CuL¹Hal₂ and CuL²Hal₂, possess interesting magnetic properties [1, 2]. For example, at very low temperatures CuL¹Cl₂ and CuL¹Br₂ are ferromagnets [2](T _c ≈ 3.3 and 6.5 K, respectively). To explain the magnetic behavior of copper(II) halide complexes with the above nitrogen heterocycles it is generally assumed that the complexes are polynuclear chain compounds in which the copper atoms are bridged by two halogen ions and bridging bidentate heterocycle molecules (coordination of N1 and N2 atoms). This hypothesis is made on the basis of the X-ray diffraction analysis of CuL¹Cl₂ [3]. It is interesting to perform an X-ray diffraction study of CuL²Cl₂ and CuL2Br2; this is important for obtaining reliable magnetostructural correlations for this group of compounds. In this study, we investigated single crystals of the complexes; this demanded choosing special conditions of synthesis, which differ from the conditions suggested for the synthesis of polycrystals in [1]. In this communication we report on the results of synthesis and X-ray diffraction analysis of the single crystals of the coordination compound CuL²Cl₂. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 1, pp. 207–212, January–February, 1997.     

Metallkomplexe mit N2O2S2‐Koordinationssphäre. Synthese und Charakterisierung der Cobalt(II)‐, Nickel(II)‐ und Kupfer(II)‐Komplexe eines 15‐ und eines 16‐gliedrigen N,N′‐bis(2‐hydroxyethyl)‐funktionalisierten makrocyclischen Liganden

Metal Complexes with N₂O₂S₂ Donor Set. Synthesis and Characterization of the Cobalt(II), Nickel(II), and Copper(II) Complexes of a 15‐ and a 16‐Membered Bis(2‐hydroxyethyl) Pendant Macrocyclic Ligand The macrocyclic ligands 6, 10‐bis(2‐hydroxyethyl)‐7, 8, 9, 11, 17, 18‐hexahydro‐dibenzo‐[e, n][1, 4, 8, 12]‐dithiadiaza‐cyclopentadecine ( 1 ) (L¹) and 5, 13‐bis(2‐hydroxyethyl)‐7, 8, 9, 10, 16, 17, 18, 19, 20‐nonahydro‐dibenzo‐[g, o][1, 9, 5, 13]‐dithiadiaza‐cyclohexadecine (L⁴) have been prepared. They form the stable complexes [CoL¹(‐H)CoL¹](ClO₄)₃ ( 2 ), [NiL¹](ClO₄)₂·MeOH ( 3 ), Λ‐[CuL¹](ClO₄)₂·MeOH ( 4a ) and rac‐[CuL¹](ClO₄)₂·MeOH ( 4b ), [NiL⁴](ClO₄)₂ ( 5 ), and [CuL⁴](ClO₄)₂ ( 6 ). The compounds 1 to 6 have been characterized by standard methods and single‐crystal X‐ray diffraction. In the complexes 2 to 6 the metal atoms are octahedrally coordinated by the N₂O₂S₂ donor set of the ligands. L¹ and L⁴ are folded herein along the N···M···S‐ and the N···M···N′‐axes, respectively. This results at the metal atom in a all‐cis‐configuration for the complexes of L¹ and a trans‐N₂‐cis‐O₂‐cis‐S₂‐configuration for the complexes of L⁴. The cobalt(II) complex 2 is a dimer, bridged by a rather short hydrogen bridge of 2.402(12)Å length. The copper(II) complexes of L¹ and L⁴ differ with respect to the Jahn‐Teller‐distortion.