Binary and Ternary Complexes of Copper(II) Involving N,N,N′,N′-Tetramethylethylenediamine (Me4en) and Various Biologically Relevant Ligands

Binary and ternary complexes of copper(II) involving N,N,N′,N′-tetramethylethylene-diamine (Me₄en) and various biologically relevant ligands containing different functional groups are investigated. The ligands (L) used are dicarboxylic acids, amino acids, peptides and DNA unit constituents. The ternary complexes of amino acids, dicarboxylic acids or peptides are formed by simultaneous reactions. The results showed the formation of Cu(Me₄en)(L) complexes with amino acids and dicarboxylic acids. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. Peptides form both Cu(Me₄en)(L) complexes and the corresponding deprotonated amide species Cu(Me₄en)(LH₋₁). The ternary complexes of copper(II) with (Me₄en) and DNA are formed in a stepwise process, whereby binding of copper(II) to (Me₄en) is followed by ligation of the DNA components. DNA constituents form both 1:1 and 1:2 complexes with Cu(Me₄en)²⁺. The concentration distribution of the complexes in solution was evaluated. [Cu(Me₄en)(CBDCA)] and [Cu(Me₄en)(malonate)] are isolated and characterized by elemental analysis and infrared measurements.     

Complex Formation Reactions of (2,2′-dipyridylamine)copper(II) with Various Biologically Relevant Ligands. The Kinetics of Hydrolysis of Amino Acid Esters

Binary and ternary copper(II) complexes involving 2,2′-dipyridylamine (DPA) and various biologically relevant ligands containing different functional groups are investigated. The ligands used are dicarboxylic acids, amino acids, peptides and DNA unit constituents. The ternary complexes of amino acids, dicarboxylic acids or peptides are formed by simultaneous reactions. The results showed the formation of 1:1 complexes with amino acids and dicarboxylic acids. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. Peptides form both 1:1 complexes and the corresponding deprotonated amide species. The ternary complexes of copper(II) with DPA and DNA are formed in a stepwise process, whereby binding of copper(II) to DPA is followed by ligation of the DNA components. DNA constituents form both 1:1 and 1:2 complexes with Cu(DPA)²⁺. The concentration distribution of the complexes in solution was evaluated. [Cu(DPA)(CBDCA)], [Cu(DPA)(malonate)] and [Cu(DPA)(oxalate)] were isolated and characterized by elemental analysis, i.r. and magnetic measurements. Spectroscopic studies of [Cu(DPA)(malonate)] revealed that the complex exhibits square planner coordination with copper(II). The hydrolysis of glycine methyl ester (MeGly) is catalyzed by the Cu(DPA)²⁺ complex. The reaction has been studied by a pH-state technique over the pH range 5.8–6.8 at 25 °C and I=0.1 mol dm⁻¹. The kinetic data fits assuming that the hydrolysis proceeds in two steps. The first step, involving coordination of the amino acid ester by the amino and carboxylic group, is followed by the rate-determining attack by the OH⁻ ion. The second step involves equilibrium formation of the hydroxo-complex, Cu(DPA)(MeGly)(OH), followed by intramolecular attack.     

Ternary complexes involving copper(II) and amino acids,peptides and DNA constituents. The kinetics of hydrolysis of α-amino acid esters

Binary and ternary complexes of copper(II) involving picolylamine (Pic) and amino acids, peptides (HL) or DNA constituents have been investigated. Ternary complexes of amino acids or peptides are formed by simultaneous reactions. Amino acids form the Cu(Pic)L complex, whereas peptides form Cu(Pic)L and Cu(Pic)(LH_–1). The ternary complexes of copper(II) with picolylamine and DNA are formed in a stepwise process, whereby binding of copper(II) to picolylamine is followed by ligation of the DNA components. The stability of the ternary complexes is compared with the stabilities of the corresponding binary complexes. The hydrolysis of glycine methyl ester (MeGly) is catalysed by the Cu(pic)²⁺ complex. The kinetic data is fitted assuming that the hydrolysis proceeds in two steps. The first step, involving coordination of the amino acid ester by the amino and carbonyl groups, is followed by rate-determining attack by the OH^– ion. The second step involves equilibrium formation of the hydroxo-complex, Cu(pic)(MeGly)(OH), followed by intramolecular attack.     

Synthesis,characterization, equilibrium studies,and biological activity of complexes involving copper(II), 2-aminomethylthiophenyl-4-bromosalicylaldehyde Schiff base,and selected amino acids

Ternary complexes of copper(II) with 2-aminomethylthiophenyl-4-bromosalicylaldehyde (ATS) and some amino acids have been isolated and characterized by elemental analyses, IR, magnetic moment, molar conductance, UV–vis, mass spectra, and ESR. The proposed general formulas of the prepared complexes are [Cu(ATS)(AA)]·nH₂O (where AA?=?glycine, alanine, and valine). The low molar conductance values suggest the non-electrolytic nature of the complexes. IR spectra show that ATS is coordinated to copper in a bidentate manner through azomethine-N and phenolic-OH. The amino acids also are monobasic bidentate ligands via amino and ionized carboxylate groups. The magnetic and spectral data indicate the square-planar geometry of Cu(II) complexes. The geometry of the Cu(II) complexes has been fully optimized using parameterized PM3 semiempirical method. The Cu–N bond length is longer than that of Cu–O in the isolated complexes. Also, information is obtained from calculations of molecular parameters for all complexes including net dipole moment of the metal complexes, values of binding energy, and lipophilicity value (log P). The antimicrobial activity studies indicate significant inhibitory activity of complex 3 against the selected types of bacteria. The mixed ligand complexes have also been studied in solution state. Protonation constants of ATS and amino acids were determined by potentiometric titration in 50% (v/v) DMSO–water solution at ionic strength of 0.1?M NaCl. ATS has two protonation constants. The binary and ternary complexes of copper(II) involving ATS and some selected amino acids (glycine, alanine, and valine) were examined. Copper(II) forms [Cu(ATS)], [Cu(ATS)₂], [Cu(AA)], [Cu(AA)₂], and [Cu(ATS)(AA)] complexes. The ternary complexes are formed in a simultaneous mechanism.     

Equilibrium Studies of Binary and Mixed-Ligand Complexes of Zinc(II) Involving 2-(Aminomethyl)-Benzimidazole and Some Bio-Relevant Ligands

Binary and mixed-ligand complexes of zinc(II) involving 2-(aminomethyl)-benzimidazole (AMBI) and amino acids, peptides (HL) or DNA constituents have been investigated. Ternary complexes of amino acids or peptides are formed simultaneously. Amino acids form the complex Zn(AMBI)L, whereas amides form two complex species Zn(AMBI)L and Zn(AMBI)(LH_?1). The ternary complexes of zinc(II) with AMBI and DNA are formed in a stepwise process, whereby binding of zinc(II) to AMBI is followed by ligation of the DNA constituents. The stability of ternary complexes is quantitatively compared with their corresponding binary complexes in terms of the parameters ??log₁₀ K, log₁₀ ??_stat and log₁₀ X. The effect of the side chains of amino acid ligands (??_R) on complex formation is discussed. The values of ??log₁₀ K indicated that the ternary complexes containing aromatic amino acids are significantly more stable than the complexes containing alkyl- and hydroxyalkyl-substituted amino acids. This may be taken as evidence for a stacking interaction between the aromatic moiety of AMBI and the aromatic side chains of the bio-active ligands. The concentration distributions of various species formed in solution were also evaluated as a function of the pH.     

Potentiometric,spectral characterization,and antioxidant activity studies of ternary complexes involving Cu(II) and carbamoylcholine chloride drug with amino acids

A potentiometric method was used to determine the stability constants for the various complexes of copper(II) with carbamoylcholine chloride (C) drug as a ligand in the presence of some biorelevant amino acid constituents like glycine (Gly), alanine (Ala), valine (Val), proline (Pro), β-phenylalanine (Phe), S-methylcysteine (Met), threonine (Thr), ornithine (Orn), lysine (Lys), histidine (Hisd), histamine (Hist), and imidazole (Imz) as ligands (L). Stability constants of complexes were determined at 25°C and I = 0.10 mol/L NaNO₃. The relative stability of each ternary complex was compared with that of the corresponding binary complexes in terms of Δlog K and % R.S. values. Cu(II) complexes of drug C were synthesized in 1:1 and 1:1:1 M ratios of copper to drug [Cu(C)(NO₃)₂] (1) and copper to drug to glycine[Cu(C)(Gly)(NO₃)].NO₃ (2), respectively. Glycine ternary complex with drug and copper [Cu(C)(Gly)(NO₃)].NO₃ was considered as representative amino acid. The complexes 1 and 2 were isolated and characterized using various physicochemical and spectral techniques. Both complexes 1 and 2 were found to have magnetic moments corresponding to one unpaired electron. The possible square planar and square-pyramidal geometries of the copper (II) complexes were assigned on the basis of electron paramagnetic resonance (EPR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), ultraviolet–visible (UV–Vis) and infrared (IR) spectral studies, and the discrete Fourier transform method from DMOL3 calculations. Antioxidant activities of all the synthesized compounds were also investigated.     

Stabilities of the Ternary Complexes of Copper(II) with Substituted 1,10-Phenanthrolines and Some Amino Acids in Aqueous Solution

In this study the binary and ternary complexes of copper(II) with substituted 1,10-phenanthrolines [s-phen: 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (dmphen) and 5-nitro-1,10-phenanthroline (nphen)] and l-amino acids [aa: l-phenylalanine (phe), l-tyrosine (tyr) and l-tryptophan (trp)] have been investigated using potentiometric methods in 0.1 mol·L^?1 KCl aqueous ionic media at 298.2 K. The protonation constants of the ligands and the stability constants of the binary and ternary complexes of Cu(II) with the ligands were calculated from the potentiometric data using the “BEST” software package. It was inferred that the aromatic 1,10-phenanthrolines act as a primary ligand in the ternary complexes, while the oxygen and nitrogen donor-containing amino acids are secondary ligands. The observed values of Δlog₁₀ K indicate that the ternary complexes are more stable than the binary ones, suggesting no interaction takes place between the ligands in the ternary complexes. The magnitudes of the measured stability constants of all of the ternary complexes are in the order [Cu(s-phen)(trp)]⁺ > [Cu(s-phen)(tyr)]⁺ > [Cu(s-phen)(phe)]⁺, which is identical to the sequence found for the binary complexes of Cu(II) with the amino acids. When the substituted 1,10-phenanthroline is changed, the stability constants of the ternary complexes decrease in the following order: [Cu(dmphen)(aa)]⁺ > [Cu(phen)(aa)]⁺ > [Cu(nphen)(aa)]⁺.     

Mixed Ligand Complex Formation Reactions and Equilibrium Studies of Cu(II) with Bidentate Heterocyclic Alcohol (N,O) and Some Bio-Relevant Ligands

The formation equilibria of copper(II) complexes and the ternary complexes Cu(HMI)L (HMI=4-Hydroxymethyl-imidazole, L=amino acid, amides or DNA constituents) have been investigated. Ternary complexes are formed by a simultaneous mechanism. The results showed the formation of Cu(HMI)L and Cu(HMI,H₋₁)(L) complexes. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters Δlog ₁₀ K and log ₁₀ X. The effect of the side chains of amino acid ligands (Δ_R) on complex formation was discussed. The concentration distributions of various species formed in solution were also evaluated as a function of pH. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants are investigated. The effects of dioxane as a solvent, on the protonation constant of HMI and the formation constants of Cu^II–HMI complexes, were discussed.     

Coordination properties of tridentate (N,O,O) heterocyclic alcohol (PDC) with Cu(II). Mixed ligand complex formation reactions of Cu(II) with PDC and some bio-relevant ligands

The formation equilibria of copper(II) complexes and the ternary complexes Cu(PDC)L (PDC=2,6-bis-(hydroxymethyl)-pyridine, HL=amino acid, amides or DNA constituents) have been investigated. Ternary complexes are formed by a simultaneous mechanism. The results showed the formation of Cu(PDC)L, Cu(PDC, H(-1))(L) and Cu(PDC, H(-2))(L) complexes. The concentration distribution of the complexes in solution is evaluated as a function of pH. The effect of dioxane as a solvent on the protonation constant of PDC and the formation constants of Cu(II) complexes are discussed. The thermodynamic parameters DeltaH degrees and DeltaS degrees calculated from the temperature dependence of the equilibrium constants are investigated.     

Ternary and binary copper(II) complexes: synthesis,characterization, ROS-inductive,proteasome inhibitory,and anticancer properties

Three ternary copper(II) complexes, [Cu(phen)(L-phe)Cl]·2H₂O, [Cu(phen)(L-leu)Cl]·4½H₂O, and [Cu(phen)(L-tyr)Cl]·3H₂O, and four binary copper(II) complexes, [Cu(phen)Cl₂]_, Cu(L-phe)₂·½H₂O, Cu(L-leu)₂·½H₂O, and Cu(L-tyr)₂·H₂O (where phen = 110-phenanthroline, L-phe = L-phenylalanine, L-tyr = L-tyrosine, L-leu = L-leucine and Cl^- = chloride), were synthesized and characterized by elemental analysis, spectroscopic techniques (FTIR, UV–visible, fluorescence spectroscopy), magnetic susceptibility, molar conductivity, and lipophilicity measurement. X-ray diffraction determination of a single crystal of [Cu(phen)(L-tyr)Cl] showed two independent molecules in the asymmetric unit, each with the same distorted square pyramidal geometry about copper(II). p-Nitrosodimethylaniline assay revealed that the three ternary complexes were better inducers of reactive oxygen species over time than binary complexes, CuCl₂, and free ligands. All the copper(II) complexes in this series inhibited the three proteolytic activities in the order Trypsin-like > Caspase-like > Chymotrypsin-like. In terms of anticancer properties, the copper(II)-phen complexes had GI50 values of less than 4 μM against MCF-7, HepG2, CNE1 and A549 cancer cell lines, more potent than cisplatin.     

Copper(II) complexes of imino-bis(methyl phosphonic acid) with some bio-relevant ligands. Equilibrium studies and hydrolysis of glycine methyl ester through complex formation

Binary and ternary complexes of Cu(II) involving imino-bis(methyl phosphonic acid) (IdP) abbreviated as H₄A and some selected bio-ligands, amino acids, peptides and DNA constituents (L), were examined. Cu(II) forms CuA and CuAH complexes with IdP. Ternary complexes are formed in a stepwise mechanism whereby iminodiphosphonic acid binds to Cu(II), followed by coordination of amino acid, peptide or DNA. The concentration distribution of the various complex species has been evaluated. The kinetics of base hydrolysis of glycine methyl ester in the presence of Cu(II)-IdP was studied in aqueous solution at different temperatures, and in dioxane-water solutions of different compositions at 25°C. The activation parameters are evaluated and discussed.     

Synthesis,crystal structure,stability studies,DNA/albumin interactions,and antimicrobial activities of two Cu(II) complexes with amino acids and 5-nitro-1,10-phenanthroline

One-dimensional (1-D) coordination polymer and mononuclear copper(II) complexes, ([Cu(nphen)(asn)]ClO₄)_n (1) and [Cu(nphen)(gln)(H₂O)]ClO₄·H₂O (2) (nphen = 5-nitro-110-phenanthroline, asn = asparagine, gln = glutamine), have been synthesized and characterized by IR spectroscopy, ESI-MS, CHN analysis, and single-crystal X-ray diffraction. These binary and ternary complexes of copper(II) with nphen, asn, and gln have been investigated using potentiometric methods in 0.1 M KCl aqueous ionic media at 298.2 K. The protonation constants of the ligands and the stability constants of 1 and 2 have been calculated from the potentiometric data using the “BEST” software package. The potentiometric results have been analyzed using the “SPE” software package, and the distribution curves for the copper-containing species have been determined for the ternary systems. The CT-DNA-binding properties of these complexes have been investigated by thermal denaturation measurements and both absorption and emission spectroscopy. Further, the interaction of these complexes with bovine serum albumin (BSA) and human serum albumin (HSA) has been investigated using absorption and emission spectroscopy. The thermodynamic parameters, free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) were calculated by the van’t Hoff equation and discussed. The distances between the serum albumins and 1 and 2 have been obtained according to fluorescence resonance energy transfer (FRET). Conformational changes of serum albumins have been observed from synchronous fluorescence technique. The antimicrobial activity of the complexes has also been tested on some bacteria. The effect of different amino acids on the copper(II) complexes are discussed.     

Mixed-Ligand Complex Formation Equilibria of Copper(II) with 6-Methylpicolinic Acid and Some Amino Acids

In this work, the ternary complex formation among copper(II), 6-methylpicolinic acid (H6Mepic) as primary ligand, and the amino acids aspartic acid (H₂Asp), glutamic acid (H₂Glu) and histidine (HHis) as secondary ligands, were studied in aqueous solution at 25 °C using 1.0 mol·dm^?3 KNO₃ as the ionic medium. Analysis of the potentiometric data using the least squares computational program LETAGROP indicates formation of the species [Cu(6Mepic)]⁺, Cu(6Mepic)(OH), [Cu(6Mepic)(OH)₂]^?, Cu(6Mepic)₂ and [Cu(6Mepic)₃]^? in the binary Cu(II)–H6Mepic system. In the ternary Cu(II)–H6Mepic–H₂Asp system the complexes [Cu(6Mepic)(H₂Asp)]⁺, Cu(6Mepic)(HAsp), [Cu(6Mepic)(Asp)]^? and [Cu(6Mepic)(Asp)(OH)]^2? were observed. In the case of the Cu(II)–H6Mepic–H₂Glu system the complexes Cu(6Mepic)(HGlu), [Cu(6Mepic)(Glu)]^?, [Cu(6Mepic)(Glu)(OH)]^2? and [Cu(6Mepic)(glu)(OH)₂]^3? were detected. Finally, in the Cu(II)–H6Mepic–HHis system the complexes [Cu(6Mepic)(HHis)]⁺, Cu(6Mepic)(His) and [Cu(6Mepic)(His)(OH)]^? were observed. The species distribution diagrams as a function of pH are briefly discussed.     

Homo‐ and heteropolynuclear copper(II) complexes containing a new diimine–dioxime ligand and 1,10‐phenanthroline: synthesis,characterization, solvent‐extraction studies,catalase‐like functions and DNA cleavage abilities

A series of homo‐, heterodinuclear and homotrinuclear copper(II) complexes containing a new Schiff base ligand and 1,10‐phenanthroline were synthesized. Based on results of elemental analyses, FTIR, ¹H‐ and ¹³C‐NMR spectra, conductivity measurements and magnetic susceptibility measurements, the complexes had general compositions {[Cu(L)(H₂O)M(phen)₂](ClO₄)₂ [M = Cu(II), Mn(II), Co(II)]} and {[Cu₃(L)₂(H₂O)₂](ClO₄)₂}. The metal:L:phen ratio is 2:1:2 for the dinuclear copper(II) complexes and the metal:L ratio was 3:2 for the trinuclear copper(II) complex. The liquid–liquid extraction of various transition metal cations [Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cd(II), Hg(II)] from the aqueous phase to the organic phase was carried out using the diimine–dioxime ligand. It was concluded that the ligand can effectively be used in solvent extraction of copper(II) from the aqueous phase to the organic phase. Furthermore, catalytic activitiy of the complexes for the disproportionation of hydrogen peroxide was also investigated in the presence of imidazole. Dinuclear copper(II)–manganese(II) complex has some similarity to manganese catalase in structure and activity. The interaction between these complexes and DNA has also been investigated by agarose gel electrophoresis; we found that the homo‐ and heterodinuclear copper complexes can cleave supercoiled pBR322 DNA to nicked and linear forms in the presence of H₂O₂. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis,Characterization, Structural Description,Micellization Behavior,DNA Binding Study and Antioxidant Activity of 4, 5 and 6-Coordinated Copper(II) and Zinc(II) Complexes

Four mononuclear copper(II) and zinc(II) complexes were synthesized by the reaction of copper and zinc salts with 3,4-dichlorophenylactic acid, 2-bromophenylactic acid, biphenylacetic acid (O-donor ligand) and bipyridine (N-donor ligands) having the general formulae [(L)₂Cu(bp)(H₂O)] ( 1 ), [(BpA)₂Cu(bp)] ( 2 ), [(L)₂Zn(bp)(H₂O)] ( 3 ) and [(L*)₂Zn(bp)] ( 4 ) (L = 3,4-dichlorophenylacetate, L* = 2-bromophenylacetate bp = bipyridine, and BpA = biphenylacetate). Structures of all compounds were characterized through FT-IR spectroscopy and X-ray diffraction analysis. FT-IR spectra of all complexes confirmed the binding mode of Cu-O and Zn-O. XRD data revealed that complexes 1 – 3 exhibited distorted octahedral arrangement, whereas complex 4 has a distorted tetrahedral environment. Micellization behavior was examined with anionic surfactant (SDS) by conductance measurement as well as absorption spectral analysis. DNA binding study was assessed through viscosity measurement and UV/Vis spectrophotometry. DPPH free radical scavenging assay was measured by UV/Vis spectrophotometry. The results showed nice biological potential of all the complexes.     

Three new binuclear copper(II) complexes with isonicotinic acid N-oxide: syntheses,crystal structures and properties

Three new copper(II) complexes with isonicotinic acid N-oxide (HL) and 1,10-phenanthroline (phen) as ligands, [Cu(L)(phen)(H₂O)]₂(NO₃)₂···2H₂O (1), [Cu(L)(phen)(H₂O)]₂(ClO₄)₂···2H₂O (2), and [Cu(L)(phen)Br]₂- [Cu(L)(phen)(H₂O)]₂Br₂···6H₂O (3) have been synthesized and structurally characterized. The structures of all three complexes feature a Cu₂ dimer formed by two Cu(II) ions interconnected by two bridging ligands. Each copper(II) ion has a distorted square pyramidal coordination geometry with elongated axial coordination by an aqua ligand or halogen anion. The isonicotinic acid N-oxide anion is bidentate, being coordinated to two Cu(II) ions through its N-O oxygen and one of its carboxylate oxygen atoms. Magnetic susceptibility measurements show a Curie–Weiss paramagnetic behavior characteristic of one unpaired electron for a copper(II) ion for all three complexes.     

A new ternary Cu (II) complex with 4,7-dimethyl-1,10-phenanthroline and NOO-type tridentate Schiff base ligand: Synthesis,crystal structure,biomacromolecular interactions,and radical scavenging activities

NOO-type tridentate Schiff base, N-salicylidene-2-aminobenzoic acid, (H₂L), and its ternary Cu (II) complex containing H₂L Schiff base and 4,7-dimethyl-1,10-phenanthroline (4,7-dmphen), [Cu(4,7-dmphen)(H₂L)]₂7H₂O, have been synthesized and characterized by CHN analysis, ESI-MS, FTIR, and single-crystal X-ray diffraction techniques. The interaction of alone H₂L Schiff base ligand and ternary Cu (II) complex with biomacramolecules {calf thymus DNA (CT-DNA) and bovine serum albumin (BSA)} has been investigated by electronic absorption and fluorescence spectroscopy. The experimental results indicate that H₂L Schiff base ligand and ternary Cu (II) complex bind to CT-DNA by means of a moderate intercalation mode. Furthermore, the fluorescence quenching mechanism between H₂L Schiff base ligand and ternary Cu (II) complex with BSA possesses a static quenching process. Radical scavenging activity of H₂L Schiff base ligand and ternary Cu (II) complex was measured in terms of EC₅₀, using the DPPH and H₂O₂ methods. Biomacromolecule interactions and scavenging activity studies revealed that ternary Cu (II) complex yielded better results than H₂L Schiff base ligand alone.     

Binary and Ternary Metal Complexes Derived from Cu Acetate with Some Sulfur-Containing Chemotherapeutic Agents

Two ternary complexes, [Cu₂(Pir)(Pen)(OH)(Ac)H₂O] and [Cu(Pir)(Cap)(Ac)] ½H₂O (where, Pen = D-penicillamine, Cap = captopril, and Pir = piroxicam) have been synthesized and characterized using elemental analyses, spectroscopic analyses (IR, UV-vis, MS), thermal analyses (TGA), conductance measurements, and magnetic measurements. The binary complexes, [Cu₂(Pen)(OH)₂(H₂O)₂] 4H₂O and [Cu(Cap)Ac] 3/2H₂O, have also been prepared and characterized by these techniques to facilitate the interpretation of the mixed ligand complexes. The results show that D-penicillamine can coordinate two copper atoms through amino nitrogen, and thiol sulfur after displacement of a hydrogen atom. At the same time, the ligand coordinates to the second copper atom through a carboxyl group after displacement of a hydrogen from the latter group. Captopril coordinates through thiol sulfur and carbonyl oxygen. Piroxicam coordinates as a neutral bidentate ligand in the keto form through carbonyl oxygen and pyridyl nitrogen. The magnetic moment measurements of complexes containing captopril indicate the reduction of Cu(II) to Cu(I) by the thiol group.     

Synthesis,characterization and non-linear optical properties of two mononuclear Cu(II) complexes of 2,6-bis(1-butylbenzimidazol-2-yl)pyridine

Two copper(II) complexes, [Cu(L)(N₃)₂]·MeOH and [Cu(L)(NCS)₂]·MeOH, were prepared and characterized by spectroscopic, analytical, and quantum chemical studies, where L is 2,6-bis(1-butylbenzimidazol-2-yl)pyridine. X-ray quality crystals of [Cu(L)(N₃)₂]·MeOH were obtained by slow evaporation of MeOH solution of the complex. Molecular structure of [Cu(L)(N₃)₂]·MeOH was determined by X-ray crystallography. The asymmetric unit contains one [Cu(L)(N₃)₂] and one MeOH molecule. Cu(II) in [Cu(L)(N₃)₂]·MeOH is five-coordinate, bonded to five nitrogens (three from L and two from two azide anions). Coordination geometry around Cu(II) center is distorted square-pyramidal with τ value of 0.065. Optimized geometries, IR spectra, and non-linear optical properties of the complexes were obtained by computational studies based on density functional theory (DFT) with M062X method. NLO properties of these complexes were investigated computationally and both complexes exhibit better NLO properties than urea.     

Mixed-Ligand Complexes of 2-(Aminomethyl)benzimidazole Palladium(II) with Various Biologically Relevant Ligands

cis-Dichloro(2-(aminomethyl)benzimidazole)palladium(II), [Pd(AMBI)Cl₂], was synthesized and characterized. The stoichiometry and stability constants of the complexes formed between [Pd(AMBI)(H₂O)₂]²⁺ with various biologically relevant ligands containing different functional groups are investigated. The ligands used are dicarboxylic acids, amino acids, peptides and DNA constitutents. The results show the formation of 1:1 complexes with amino acids and dicarboxylic acids. The effect of the chelate ring size of the dicarboxylic acid complexes on their stability constants is examined. Peptides form both 1:1 complexes and the corresponding deprotonated amide species. Structural effects of the peptide on the amide deprotonation are investigated. DNA pyrimidinic constituents such as uracil, uridine, thymidine and thymine form 1:1 and 1:2 complexes, whereas purinic constituents such as inosine 5′-monophosphate (5′-IMP) and guanosine 5′-monophosphate (5′-GMP) form only 1:1 complexes. The concentration distribution of the complexes in solution was evaluated. The effect of increasing chloride ion concentration on the formation constant of CBDCA with Pd(AMBI)²⁺ was reported.