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)]⁺.     

Cu (II) tyrosinate complexes containing methyl substituted phenanthrolines: Synthesis,X‐ray crystal structures,biomolecular interactions,antioxidant activity,ROS generation and cytotoxicity

In this paper, three new copper (II) complexes, [Cu(4‐mphen)(tyr)(H₂O)]ClO₄ (1) , [Cu(5‐mphen)(tyr)(H₂O)]ClO₄·1.5H₂O (2) and [Cu (tmphen)(tyr)(NO₃)]0.5H₂O (3) (4‐mphen: 4‐methyl‐1,10‐phenanthroline, 5‐mphen: 5‐methyl‐1,10‐phenanthroline, tmphen: 3,4,7,8‐tetramethyl‐1,10‐phenanthroline and tyr: L‐tyrosine), were synthesized and characterized using elemental analyses, FT‐IR, ESI‐MS, cyclic voltammetry and single‐crystal X‐ray diffraction. It was found that the complexes adopt a distorted five‐coordinate square pyramidal geometry. The interaction of the three complexes with calf thymus DNA was also investigated using UV–visible absorption spectra, ethidium bromide and Hoechst 33258 displacement assay and thermal denaturation. The DNA cleavage activity of the complexes, monitored using gel electrophoresis, showed significant damage of the pUC19 plasmid DNA. Binding activity of bovine serum albumin (BSA) reveals that these complexes can strongly quench the fluorescence of BSA through a static quenching mechanism. The results suggested that interaction of the complexes with DNA occurred through a partial intercalation into the minor grooves of DNA. In addition, interaction of the complexes with bovine serum albumin quenched the fluorescence emission of the tryptophan residues of the protein binding constants and thermodynamic parameters were obtained from the fluorescence quenching experiments at different temperatures. Free radical scavenging activities of the complexes were determined by various in vitro assays such as 1,1‐diphenyl‐2‐picryl‐hydrazyl free radicals (DPPH˙) and H₂O₂ scavenging methods. In addition, the cytotoxicity of these complexes in vitro on tumor cell lines (Caco‐2 and MCF‐7) was examined by XTT and showed better antitumor effect on the tested cells. ROS (reactive oxygen species) and comet experiments are consistent with each other and these complexes lead to DNA damage via the production of ROS. The effect of the hydrophobic properties of the synthesized complexes on DNA and BSA binding activities were discussed.     

Methyl substituent effect on one‐dimensional copper(II) coordination polymers containing biologically active ligands: Synthesis,characterization, DNA interactions and cytotoxicities

Three novel water‐soluble copper(II) complexes – {[Cu(phen)(trp)]ClO₄·3H₂O}_n ( 1 ), {[Cu(4‐mphen)(trp)]ClO₄·3H₂O}_n ( 2 ) and [[Cu(dmphen)(trp)(MeOH)][Cu(dmphen)(trp)(NO₃)]]NO₃ ( 3 ) (phen: 1,10‐phenanthroline; 4‐mphen: 4‐methyl‐1,10‐phenanthroline; dmphen: 4,7‐dimethyl‐1,10‐phenanthroline; trp: l ‐tryptophan) – have been synthesized and characterized using various techniques. Complexes 1 and 2 are isostructural, and exist as one‐dimensional coordination polymers. Complex 3 consists of two discrete copper(II) complexes containing [Cu(trp)(dmphen)(MeOH)]⁺, [Cu(trp)(dmphen)(NO₃)] and one nitrate anion. The binding interaction of the complexes with calf thymus DNA (CT‐DNA) was investigated using thermal denaturation, electronic absorption and emission spectroscopic methods, revealing that the complexes could interact with CT‐DNA via a moderate intercalation mode. The binding activity of the complexes to CT‐DNA follows the order: 3  >  2 > 1 . The pUC19 DNA cleavage activity of the complexes was investigated in the absence and presence of external agents using the agarose gel electrophoresis method. Especially, in the presence of H₂O₂ as an activator, the pUC19 DNA cleavage abilities of the complexes are clearly enhanced at low concentration. Addition of hydroxyl radical scavenger dimethylsulfoxide shows a marked inhibition of the pUC19 DNA cleavage activity of the complexes. In vitro cytotoxic effect of the complexes was examined on human tumor cell lines (Caco‐2, A549 and MCF‐7) and healthy cells (BEAS‐2B). The potent cytotoxic effect of complex 3 , with IC₅₀ values of 1.04, 1.16 and 1.72 μM, respectively, is greater relative to clinically used cisplatin (IC₅₀ = 22.70, 31.1 and 22.2 μM) against the Caco‐2, A549 and MCF‐7 cell lines.     

Syntheses,characterizations and SOD-like activities of ternary copper(II) complexes with 1,10-phenanthroline and L- α -amino acids

Three new complexes, [Cu(phen)(L-argH⁺)Cl]Cl?·?2.5H₂O (1), [Cu(phen)(L-leu)(H₂O)]Cl?·2.5H₂O (2) and [Cu(phen)(L-met)(H₂O)]Cl?·?2H₂O (3), where phen?=?1,10-phenanthroline, L-arg?=?L-argininate, L-leu?=?L-leucinate, and L-met?=?L-methioninate, were synthesized and characterized by elemental analysis, molar conductivity, IR and UV-Vis spectroscopies. Complex 1 was structurally characterized by single-crystal X-ray diffraction. The superoxide dismutase (SOD)-like activities of the three complexes were determined by the improved NBT method. The results show that the complexes have high superoxide dismutase-like activities and may act as good mimics for superoxide dismutases.     

Choice of a suitable hetero-aromatic nitrogen base as promoter for chromic acid oxidation of dl-mandelic acid in aqueous media at room temperature

Chromic acid oxidation of dl-mandelic acid in the presence and absence of different promoters has been studied in aqueous media under the kinetic conditions [mandelic acid]_T ? [Cr(VI)]_T and [promoter]_T ? [Cr(VI)]_T at 30 °C. The promoters used in this oxidation reaction, picolinic acid (PA), 2,2′-bipyridine (bpy), and 1,10-phenanthroline (phen), are strong chelating ligands which form complexes with most transition metal ions. The reaction is first-order with regard to [H⁺], [mandelic acid]_T, and [Cr(VI)]_T and also has first-order dependence on [promoter]_T. HCrO₄ ^? was found to be kinetically active in the absence of promoters; in the presence of promoters the Cr(VI)–promoter complexes were believed to be the active oxidants. In this path the Cr(VI)-promoter complex in each case undergoes nucleophilic attack by the mandelic acid to form a ternary complex which subsequently undergoes redox decomposition involving 3e transfer as the rate-determining step. Among the three promoters oxidation is much faster with 1,10-phenanthroline.     

Magneto-structural studies on heterobimetallic malonate-bridged M(II)Re(IV) complexes (M = Mn, Co, Ni and Cu)

The mononuclear Re(IV) compound of formula (PPh(4))(2)[ReBr(4)(mal)] (1) was used as a ligand to obtain the heterobimetallic species [ReBr(4)(μ-mal)Co(dmphen)(2)]· MeCN (2), [ReBr(4)(μ-mal)Ni(dmphen)(2)] (3), [ReBr(4)(μ-mal)Mn(dmphen)(2)] (4a), [ReBr(4)(μ-mal)Mn(dmphen)(H(2)O)(2)]·dmphen·MeCN·H(2)O (4b), [ReBr(4)(μ-mal)Cu(phen)(2)]·1/4H(2)O (5) and [ReBr(4)(μ-mal)Cu(bipy)(2)] (6) (mal = malonate dianion, dmphen = 2,9-dimethyl-1,10-phenanthroline, phen = 1,10-phenanthroline and bipy = 2,2'-bipyridine). The structures of 2 and 5 (single-crystal X-ray diffraction) are made up of neutral [ReBr(4)(μ-mal)M(AA)] dinuclear units [AA = dmphen with M = Co (2) and AA = phen with M = Cu (5)] where the metal ions are connected through a malonate ligand which exhibits simultaneously the bidentate [at the Re(IV)] and monodentate [at the M(II)] coordination modes. The carboxylate-malonate group in them adopts the anti-syn conformation with intramolecular ReM separation of 5.098(8) (2) and 4.947(2) ? (5). The magnetic properties of 1-6 were investigated in the temperature range 1.9-295 K. The magnetic behaviour of 1 is the expected for a magnetically isolated Re(IV) complex with a large value of the zero-field splitting (2D ca. -70 cm(-1)) whereas weak antiferromagnetic interactions between Re(IV) and M(II) are observed in the heterobimetallic compounds 2 (J = -0.63 cm(-1)), 3 (J = -1.37 cm(-1)), 4a (J = -1.29 cm(-1)), 5 (J = -1.83 cm(-1)) and 6 (J = -0.26 cm(-1)). Remarkably, 4b behaves as a ferrimagnetic chain with regular alternating Re(IV) and Mn(II) cations (J = -2.64 cm(-1)).     

New mononuclear copper(II) complexes from β-diketone and β-keto ester N-donor heterocyclic ligands: structure,bioactivity, and molecular simulation studies

Four new mononuclear copper(II) complexes with methyl acetoacetate and benzoylacetone in the presence of 1,10-phenanthroline and 2,2′-bipyridine were synthesized and characterized by elemental analyses, FT-IR, and UV–Vis spectroscopy. The molecular structures of complexes [Cu(MAA)(bpy)(ClO₄)] (1a), [Cu(bzac)(bpy)]ClO₄ (2a), [Cu(MAA)(phen)(ClO₄)] (1b) and [Cu(bzac)(phen)(ClO₄)] (2b) were determined by single crystal X-ray diffraction technique. 1a, 1b, and 2b are five coordinate with a distorted square pyramidal geometry and the structure of 2a consists of isolated [Cu(bzac)(bpy)]⁺ cations and perchlorate counter anions. The electrochemical studies of copper complexes in acetonitrile solution showed that Cu^II/Cu^I reduction processes are electrochemically irreversible. Cytotoxic activity of complexes was screened, including an MTT assay against gastric cancer cell line (MKN-45). The four Cu(II) complexes exhibited lethal effects against MKN-45 cell lines and the half maximal inhibitory concentration (IC₅₀) values obtained were much lower in comparison with 5-fluorouracil. In addition, MTT and migration studies revealed that benzoylacetone complexes are more active than complexes of methyl acetoacetate against the MKN-45 cancer cell lines. Docking simulations of Cu(II) complexes on DNA revealed that the most stable adducts with DNA bind in the minor groove. All complexes display a binding specificity to the A/T rich regions.     

A unique borotungstate containing a discrete Keggin-type anion and a trimeric saturated Keggin-type anion

A unique hybrid borotungstate, [Cu(En)(Phen)(H₂O)]₄[α-BW₁₂O₄₀]{[Cu(En)(Phen)]₂[Cu(En)₂ · (H₂O)]₂[Cu(En)(Phen)(H₂O)]₂[α-BW₁₂O₄₀]₃]} sd 10H₂O (I) (Phen = 1,10-phenanthroline, En = ethylenediamine), has been hydrothermally synthesized and characterized by elemental analyses, IR, and UV spectra, powder X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, and singlecrystal X-ray diffraction analysis. X-ray crystallography shows that I contains a discrete saturated Keggin-type [BW₁₂O₄₀]⁵⁻ polyoxoanion and a rare trimeric saturated Keggin-type polyoxoanion {[Cu(En)(Phen)]₂[Cu(En)₂(H₂O)]₂[Cu(En)(Phen)(H₂O)]₂[α-BW₁₂O₄₀]₃]}³⁻. It is noteworthy that I represents the first example of borotungstate containing four saturated Keggin-type units in one molecule.     

A new approach to the gas phase chemistry of ternary transition metal complexes: Ion-beam induced reactions

High Energy Cs⁺-ion bombardment of glycerol containing a suitable transition metal chloride, an amino acid (A.A.) and 1,10-phenanthroline (phen) induces the formation of singly charged ternary complexes of the type [Cat(A.A. - H) (phen)]⁺, where Cat = Cr, Mn, Fe, Co or Ni. The investigation of the complexes is performed by MS/MS experiments using a four-sector instrument. Metastable decompositions of iron containing ternary complexes [Fe(A.A. - H) (phen)]⁺ provide abundant fragment ions indicating the coordination of functionalized amino acid side chains. Fragmentation mechanisms and ion structures are discussed.     

Oxovanadium phenanthroimidazole derivatives: synthesis,DNA binding and antitumor activities

Four unsymmetrical oxovanadium phenanthroimidazole complexes, [VO(hntdtsc)(NPIP)] (1), [VO(hntdtsc)(CPIP)] (2), [VO(hntdtsc)(MEPIP)] (3) and [VO(hntdtsc)(HPIP)] (4) (hntdtsc = 2-hydroxy-1-naphthaldehyde thiosemicarbazone, NPIP = 2-(4-nitrophenyl)-imidazo[4,5-f]1,10-phenanthroline, CPIP = 2-(4-chlorphenyl)-imidazo[4,5-f]1,10-phenanthroline), MEPIP = 2-(4-methylphenyl)-imidazo[4,5-f]1,10-phenanthroline), HPIP = 2-(4-hydroxylphenyl)-imidazo[4,5-f] 1,10-phenanthroline), have been synthesized and characterized. Their DNA binding and antitumor activities were determined by biochemical methods. All four oxovanadium complexes can bind with CT-DNA by an intercalation model and can also cleave supercoiled plasmid DNA in the presence of H₂O₂. The antitumor properties and mechanism of the complexes have been analyzed by MTT assay, cell cycle analysis, apoptosis assay and Western blot analysis. The results showed that the free ligands and their corresponding complexes all possess antiproliferative activities with very low IC₅₀ values against Hela, BIU-87 and SPC-A-1 cell lines. Complex 1, which has a strongly electron-withdrawing nitro group, exhibited the best antiproliferative activities. Complex 1 caused G₀/G₁ phase arrest of the cell cycle and induced apoptosis in Hela cells. Additionally, complex 1 attenuated the phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2).This indicates that inhibition of the ERK1/2 signaling pathway may contribute to the antitumor effects of these complexes.     

诺氟沙星-铜（Ⅱ）-邻菲咯啉配合物的SOD活性及电化学性能

应用氯化硝基四氮唑蓝（NBT）-光照法研究了配合物[Cu（NFA）（phen）（H2O）]（ClO4）2（1）和[Cu（NFA）（5-NO2-phen）（H2O）]（ClO4）2（2）[NFA=1-乙基-6-氟-1,4-二氢-4-氧代-7-（1-哌嗪基）-3-喹啉羧酸（诺氟沙星）;phen=1,10-菲咯啉;5-NO2-phen=5-硝基-1,10-菲咯啉]在水溶液中的SOD活性,并用循环伏安法研究了配合物的电化学性质.结果表明：配合物（1）和（2）均具有良好的SOD活性,表观催化速率常数分别为6.32×10^7和5.12×10^7L·mol-1·s-1.     

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.     

Mono-, di-, and trinuclear phosphonate oxygen-bridged copper(II) complexes: syntheses,structures, and properties

Reactions of copper salts, zoledronic acid, and 2,2′-bipyridine/1,10-phenanthroline in aqueous ethanolic solutions afforded four phosphonate oxygen-bridged copper complexes, Cu(bipy)(H₄zdn)(HSO₄) (1), [Cu₂(bipy)₂(H₂zdn)(H₂O)(Cl)]·4H₂O (2), [Cu₂(phen)₂(H₂zdn)(H₂O)(Cl)]·2.5H₂O (3), and [Cu₃(bipy)₃(H₄zdn)(H₂zdn)(SO₄)]·5H₂O (4) (H₅zdn = zoledronic acid, bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline). The copper centers of 1–4 have square pyramidal coordination geometries. The Cu(II) ions are coordinated to bipy/phen, zoledronate, and HSO₄^?/Cl^? forming mononuclear units for 1, dinuclear for 2 and 3, and trinuclear for 4. These building units are further extended into 3-D supramolecular networks via multiple hydrogen bond interactions. Temperature-dependent magnetic properties of 2 and 4 suggest weak antiferromagnetic coupling (J = ?4.53(8) cm^?1 for 2, J = ?1.69(4) cm^?1 for 4). The antitumor activity of 2 was evaluated against the human lung cancer cell line and indicates effective time- and dose-dependent cytotoxic effects.     

Synthesis and properties of two new Cu(I) complexes based on 5,6-substituted imidazole-2,9-dimethyl-1,10-phenanthroline and triphenylphosphine

Two new Cu(I) complexes, Cu(NPIP)(PPh3)2 (1) and Cu(MPIP)(PPh3)2 (2), (NHPIP: 2-(4-nitrophenyl) imidazole-2,9-dimethyl-1,10-phenanthroline; MHPIP: 2-(4-methylphenyl)imidazole-2,9-dimethyl-1,10-phenanthroline) have been synthesized and characterized by element analysis, IR and ¹H NMR spectra. TG experiments demonstrated that the complexes were stable up to ca 230°C indicating their high thermal stability. According to fluorescence spectra, the complexes exhibited yellow emission at 602 nm under excitation at 260 nm.     

Mixed Ligand Complex Formation of Cetirizine Drug with Bivalent Transition Metal(II) Ions in the Presence of 2-Aminomethylbenzimidazole: Synthesis,Structural, Biological,pH-Metric and Thermodynamic Studies

Mononuclear copper(II), cobalt(II) and nickel(II) complexes of cetirizine (CTZ = 2-[2-[4-[(4-chlorophenyl)phenyl methyl]-piperazine-1-yl]-ethoxy]acetic acid) in the presence of 2-aminomethyl-benzimidazole·2HCl (AMBI), as a representative example of heterocyclic bases, were synthesized and studied by different physical techniques. All mixed-ligand complexes have been fully characterized with the help of elemental analyses, molecular weight determinations, molar conductance, magnetic moments and spectroscopic data. The formulae of the isolated complexes are [M(AMBI)(CTZ)(NO₃)(H₂O)₂]·nH₂O where AMBI is the neutral bidentate 2-aminomethylbenzimidazole, CTZ the deprotonated cetirizine and n = 1 for Co(II) or 0 for Cu(II) and Ni(II) complexes. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytes. The formation equilibria of the ternary complexes have been investigated. Ternary complexes are formed by a simultaneous mechanism. Stoichiometry and stability constants for the complexes formed are reported. The concentration distribution of the complexes in solution was evaluated as a function of pH. The thermodynamic parameters were calculated from the temperature dependence of the equilibrium constants and are discussed. The synthesized metal chelates have been screened for their antimicrobial activities against the selected types of Gram-positive (G⁺) and Gram-negative (G^?) bacteria. They were found to be more active against Gram positive than Gram negative bacteria. The antimicrobial activity in terms of metal ions obeys this order: Cu(II) > Ni(II) > Co(II).     

Synthesis and characterization of new organocobaloxime derivatives with asymmetric dioxime ligands

New organocobaloxime derivatives of the types [Co(HL)₂(All)X], [CoL₂(All)XB₂F₄] and [CoL₂(All)X(Cu(phen))₂](ClO₄)₂ [H₂L¹ = 4-(4-chlorophenylamino)biphenylglyoxime and H₂L² = 4-(naphthyl-1-amino)biphenylglyoxime; phen = 1,10-phenanthroline; All = Allyl; X = H₂O, py (pyridine), APy (acetylpyridine)] were synthesized and characterized by elemental analysis, molar conductance, FT-IR, ¹H NMR and magnetic susceptibility measurements. Trinuclear complexes {CoL₂(All)X[Cu(phen)]₂}(ClO₄)₂ have planar N-donor heterocyclic base [1,10-phenanthroline (phen)]. The IR spectra indicated that the complexes coordinate through the N atom of the oxime group of each ligand. The magnetic susceptibilities of the complexes indicated that they are diamagnetic (low-spin d ⁶ octahedral) except trinuclear complex which show a subnormal magnetic moment.     

Kinetic studies on chromium-glycinato complexes in acidic and alkaline media

Two solid complexes, fac–[Cr(gly)₃] and [Cr(gly)₂(OH)]₂, (where gly is glycinato ligand) were prepared and their acid-catalysed aquation products were identified. The structure of [Cr(gly)₃] was solved by X-ray diffraction, revealing a cationic 3D sublattice with perchlorate anions inside its cavities. Acid-catalysed aquation of [Cr(gly)₃] and [Cr(gly)₂(OH)]₂ leads to the same inert product, [Cr(gly)₂(H₂O)₂]⁺, in a two-stages process. At the first stage, intermediate complexes, [Cr(gly)₂(O–glyH)(H₂O)]⁺ and [Cr(gly)₂(H₂O)–OH–Cr(gly)₂(H₂O)]⁺, are formed respectively. Kinetics of the first aquation stage of [Cr(gly)₃] were studied in HClO₄ solutions. The dependencies of the pseudo first-order rate constants on [H⁺] are as follows: k _obs1H = k ₀ + k ₁ K _p1[H⁺], where k ₀ and k ₁ are rate constants for the chelate-ring opening via spontaneous and acid-catalysed reaction paths, respectively, and K _p1 is the protonation constant. The proposed mechanism assumes formation of the reactive intermediate as a result of proton addition to the coordinated carboxylate group of the didentate ligand. Some kinetic studies on the second reaction stage, the one-end bonded glycine liberation, were also done. The obtained results were analogous to those for stage I. In this case, the proposed reactive species are intermediates, protonated at the carboxylate group of the monodentate glycine. Base hydrolysis of two complexes, [Cr(gly)₂(O–gly)(OH)]⁻ and [Cr(gly)₂(OH)₂]⁻, was studied in 0.2–1.0 M NaOH. The pseudo first-order rate constants, k _obsOH, were [OH⁻] independent in the case of [Cr(gly)₂(O–gly)(OH)]⁻, whereas those for [Cr(gly)₂(OH)₂]⁻ linearly depended on [OH⁻]. The reaction mechanisms were proposed, where the OH⁻ -catalysed reaction path was rationalized in terms of formation of the reactive conjugate base, [Cr(gly)₂(OH)(O)]²⁻, as a result of OH⁻ ligand deprotonation. Activation parameters were determined and discussed.     

Syntheses of crystal structures and in vitro cytotoxic activities of new copper(II) complexes of pyridine-2,6-dicarboxylate

[Cu(pydc)(im)]_n (1), [Cu(pydc)(mim)₃]?2H₂O (2), [Cu(pydc)(ampy)(H₂O)]?H₂O (3), and [Cu(pydc)(phen)][Cu(Hpydc)₂] (4) (H₂pydc = 2,6-pyridinedicarboxylic acid or dipicolinic acid, im = imidazole, mim = 2-methylimidazole, ampy = 2-amino-4-methylpyridine, and phen = 1,10-phenanthroline) were synthesized and characterized by elemental analysis, spectroscopic measurements (UV–vis and IR spectra) and single crystal X-ray diffraction. Complexes 1, 2 and 3 were studied by thermogravimetric analysis from ambient temperature to 1100 K under nitrogen and thermal stabilities were investigated. The effects of complexes on proliferation of fibrosarcoma cells were investigated using the Quick Cell Proliferation Assay. The cell viability changes depend on the concentrations and type of complexes. According to cell proliferation/viability data, 4 was determined to be the most cytotoxic.     

Kinetics and mechanism of the substitution reactions of some monofunctional Pt(II) complexes with heterocyclic nitrogen donor molecules. Crystal structure of [Pt(bpma)(pzBr)]Cl2·2H2O

Substitution reactions of [Pt(terpy)Cl]⁺ (terpy = 2,2′;6′,2′′-terpyridine), [Pt(bpma)Cl]⁺ (bpma = bis(2-pyridylmethyl)amine), [Pt(dien)Cl]⁺ (dien = diethylenetriamine or 1,5-diamino-3-azapentane) and [Pt(tpdm)Cl]⁺ (tpdm = tripyridinedimethane) with nitrogen donor heterocyclic molecules, such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr) and imidazole (Im), were studied in aqueous 0.10 M NaClO₄ in the presence of 10 mM NaCl using variable-temperature UV–vis spectrophotometry. The second-order rate constants k₂ indicate decrease in reactivity in the order [Pt(terpy)Cl]⁺ > [Pt(bpma)Cl]⁺ > [Pt(tpdm)Cl]⁺ > [Pt(dien)Cl]⁺. The most reactive nucleophile among the heterocyclic compounds is imidazole, while pzI shows slightly higher reactivity than pzBr. Activation parameters were also determined and the negative values for entropies of activation, ΔS^≠, support an associative mode of substitution for all substitution processes. Crystal structure of [Pt(bpma)(pzBr)]Cl₂·2H₂O was determined by single-crystal X-ray analysis. The coordination geometry of the complex is distorted square-planar while the bond distance Pt–N2(pzBr) is longer than the other three Pt–N distances.     

Magnetic properties and molecular structures of binuclear (2-pyrazinecarboxylate)-bridged complexes containing Re(IV) and M(II) (M = Co, Ni)

Three novel Re(iv) compounds, the mononuclear complex Bu(4)N[ReBr(5)(Hpyzc)] (1) and the heterobimetallic complexes [ReBr(5)(mu-pyzc)M(dmphen)(2)].2CH(3)CN [M = Co (2), Ni (3)] (Hpyzc = 2-pyrazinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structure of 1 consists of [ReBr(5)(Hpyzc)](-) complex anions and tetrabutylammonium cations, Bu(4)N(+). The Re(iv) is surrounded by five bromide anions and a N-donor Hpyzc monodentate ligand, in a distorted octahedral environment. The structures of 2 and 3 consist of dinuclear units [ReBr(5)(mu-pyzc)M(dmphen)(2)], with the metal ions linked by a pyzc bridge ligand, being bidentate toward M(II) and monodentate toward Re(IV). The environment of Re(IV) is the same as in 1, whereas M(II) is six-coordinate, being surrounded by four nitrogen atoms of two bidentate dmphen ligands and one oxygen atom and one nitrogen atom of the pyzc anion. The magnetic properties of 1-3 were investigated in the temperature range 2.0-300 K. 1 shows the expected magnetic behavior for a mononuclear Re(IV) complex with a weak intermolecular antiferromagnetic coupling at low temperatures. The bimetallic complexes exhibit an intramolecular ferromagnetic coupling between Re(IV) and the M(II) ion (Co, Ni).