Crystal structures and Mössbauer spectroscopic studies of oxo-centered trinuclear chloroacetate complexes

The crystal structures of oxo-centered trineclear cobalt-iron chloroacetate complex [Co^IIFe ₂ ^III O(CH₂ClCO₂)₆(H₂O)₃]·3H₂O (1) was compared with that of previously reported trinuclear iron complex [Fe^IIFe ₂ ^III O(CH₂ClCO₂)₆(H₂O)₃]·3H₂O (2) which has an isomorphous structure to 1. Compound 1 crystallizes in space group P2₁/n with Z=4 in a unit cell of a=14.826 (4) Å, b=4.536 (8) Å, c=14.000 (4) Å, =100.32 (2)⁰ and V=2968 (11) ų. The structure was refined to R=0.75 and R_w=0.82. The coordination geometries of the three iron atoms are observed equivalent in 1 indicating a static disorder of the position among cobalt and iron atoms. Two distinct Fe^III doublets observed in Mössbauer spectra of 1 become an indistinguishable broad doublet by dehydration of crystal water. On the other hand, no significant line-broadening is observed after the dehydration in complex 2. The results indicate that the dehydration in 2 induces a local environmental change reordering of an electronic configuration around iron atoms, whereas the remaining disordering is reflected in Mössbauer spectrum after the dehydration in 1.     

Synthesis and electrochemical studies of charge-transfer complexes of thiazolidine-2,4-dione with σ and π acceptors

In the present work, we report the synthesis and characterization of novel charge-transfer complexes of thiazolidine-2,4-dione (TZD) with sigma acceptor (iodine) and pi acceptors (chloranil, dichlorodicyanoquinone, picric acid and duraquinone). We also evaluated their thermal and electrochemical properties and we conclude that these complexes are frequency dependent. Charge-transfer complex between thiazolidine-2,4-dione and iodine give best conductivity. In conclusion, complex with sigma acceptors are more conducting than with pi acceptors.     

Synthesis and characterization of two new metal–organic frameworks with interpenetrated structures and luminescent properties

Two new metal–organic compounds, [Ag₂(HADC)₂(bimh)] (1) and [Cd(ADC)(bpp)]_n (2) [H₂ADC = 1,3-adamantanedicarboxylic acid, bimh = 1,6-bis(2-methyl-imidazole-1-yl)hexane, bpp = 1,3-bis(4-pyridyl)propane], have been synthesized and characterized. Compound 1 exhibits a discrete symmetric unit with 0D→2D interpenetrating structure. Compound 2 crystallizes in a chiral space group P212121 and presents a threefold interpenetrated 3D diamondoid network containing three helical chains. Thermal stability, X-ray powder diffraction, and luminescence for 1 and 2 are also measured and discussed.     

Synthesis,characterization and antimalarial activity of new iridium–chloroquine complexes

Chloroquine base (CQ) reacts with [Ir(COD)Cl]₂ and IrCl₃ · 3H₂O to yield of Ir(CQ)Cl(COD) (1) and Ir₂Cl₆(CQ) · 3H₂O (2), respectively. Reaction of [Ir(COD)Cl]₂ with CQ in the presence of NH₄PF₆ leaded to [Ir(CQ)(Solv)₂]PF₆ (3). The three new iridium–CQ complexes were characterized by a combination of elemental analysis, IR and NMR spectroscopies and evaluated in vitro against Plasmodium beghei. Comparison of the IC₅₀ values obtained with the experimental compounds with that determined for chloroquine diphosphate indicated a higher activity for complex 2, while complexes 1 and 3 showed a similar and lower activity, respectively.     

Synthesis,Mössbauer,and IP spectroscopic studies and thermal behavior of diorganotin(IV) complexes with carbohydrate ligands

A series of diethyltin(IV) complexes with carbohydrate ligands (aldoses, polyalcohols, sugar acids, sugar amines, and di- and trisaccharides] was prepared. The compositions of the complexes were determined by standard analytical methods. The results showed that complexes formed containing the diethyltin moiety and the carbohydrate ligand in 11 ratio. The IR spectra were consistent with the presence of tin—carbohydrate oxygen vibrations in the compounds. The comparison of experimental quadrupole splitting values with those calculated on the basis of the partial quadrupole splitting (PQS) concept revealed the compounds to be of three types: complexes in with the central tin(IV) atoms are present in purely trigonal bipyramidal surroundings, ones with the tin(IV) atoms present in purely octahedral surroundings, or ones with both octahedral and trigonal bipyramidal arrangements in approximately 11 ratio. The thermal decompositions showed that some of the complexes decompose via the reduction of tin(IV) to SnO as the final tin-containing product, some of them decompose without reduction, to give SnO₂, and some decompose to give indefinite final tin-containing products.     

Phosphine σ-sydnonyl complexes of Ni,Pd, and Pt

3-R"-4-Bromosydnones 1 (R" = Me) and 2 (R" = Ph) react with complexes Ì(PR₃)_n (M = Ni, Pd, Pt) to form mononuclear phosphine -sydnonyl d⁸-complexes of trans-configuration MBr(3-R"-sydnon-4-yl)(PR₃)₂: 3, 4 (Ì = Ni, R" = Ph); 5 (M = Pd, R" = Me); 6a (M = Pd, R" = Ph); 7 (M = Pt, R" = Ph). In the reaction of bromosydnone 2 with Pd(PPh₃)₄, the cis-complex PdBr(3-Ph-sydnon-4-yl)(PPh₃)₂ (6b) is formed initially; 6b rearranges in solution to give trans-complex 6a. On heating in THF, complex 6a is converted into the binuclear [PdBr(3-phenylsydnon-4-yl)(PPh₃)]₂ complex (8). The reaction of 4-chloromercurio-3-phenylsydnone (10) with Ni(PEt₃)₄, Pd(PPh₃)₄, and Pt(PPh₃)₄ gives mononuclear NiCl(3-phenylsydnon-4-yl)(PEt₃)₂ complex (11), binuclear [PdCl(3-phenylsydnon-4-yl) (PPh₃)]₂ complex (14), and cis- and trans-bimetallic PtCl(3-phenylsydnon-4-ylmercurio)(PPh₃)₂ complexes 15a and 15b, respectively. UV irradiation of 15a and 15b in a benzene solution induces redox demercuration to yield the PtCl(3-phenylsydnon-4-ylcarbonyl)(PPh₃)₂ complex (16). In carbonylation of complexes 3, 6, and 7, CO insertion into the M--C bond occurred to form the corresponding acyl derivatives MBr(3-phenylsydnon-4-ylcarbonyl)(PR₃)₂ (17--19).     

Synthesis,spectroscopic and biological studies of metal complexes of an ONO donor pyrazolylhydrazone – Crystal structure of ligand and Co(II) complex

A new pyrazolylhydrazone, 2-(2-(1,5-dimethy-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazolyl-4-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (HL) and its Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were synthesized and structurally characterized by elemental analysis, molar conductance, magnetic measurements and spectral (IR, ¹H NMR, UV–vis, HRMS) measurements. All complexes possess ML₂ stoichiometry with L behaving as monoanionic tridentate ONO donor. Single crystal X-ray diffraction reveals that HL and CoL₂ crystallize in orthorhombic system with Pbcn space group. Hydrogen bonding interactions between molecules of CoL₂ results in the formation of an infinite zig-zag chain extending along the ‘b’ axis. EPR spectrum of Cu(II) complex at 77 K suggests mononuclear and distorted octahedral geometry for [CuL₂]. Antimicrobial activity of HL and its complexes were investigated and minimum inhibitory concentrations identified. Bacterial and fungal organisms used were gram-positive Staphylococcus aureus, gram-negative Escherichia coli, Aspergillus niger and Candida albicans.     

Di- and trinuclear Ru(II) complexes of 1,10-phenanthroline and 2,2′-bipyridine derivatives; synthesis,photophysical and electrochemical properties

Three heterotopic ligands L¹, L², and L³ based on 1,10-phenanthroline and 2,2′-bipyridine moieties have been synthesized and characterized. The Ru(II) complexes [{Ru(bpy)₂}₃(µ₃-L¹)](PF₆)₆, [{Ru(bpy)₂}₃(µ₃-L²)](PF₆)₆, and [{Ru(bpy)₂}₂(µ₂-L³)](PF₆)₄ (bpy = 2,2′-bipyridine) have been prepared by refluxing Ru(bpy)₂Cl₂·2H₂O with each ligand in ethanol. All three complexes display MLCT absorptions at around 455 nm and emissions at around 618 nm. Electrochemical studies of the complexes reveal one Ru(II)-centered quasi-reversible oxidation at around 1.32 V and three ligand-centered reductions in each case.     

Synthesis,spectroscopic characterization,thermal stability and biological studies of mixed ligand complexes of gemifloxacin drug and 2,2′-bipyridine with some transition metals

Research on Chemical Intermediates - The mixed ligand Zn(II), Zr(IV), Pd(II), Ce(IV), Th(IV), and U(VI) complexes of gemifloxacin and N-donor 2,2′-bipyridine have been prepared. These...     

Chemistry of vinylidene complexes—XXVII—new µ-vinylidene MnPt complexes with platinum-coordinated 1-adamantyl isocyanide ligand: spectroscopic,structural and electrochemical study

Transition Metal Chemistry - New binuclear MnPt µ-vinylidene complexes Cp(CO)2Mn(µ-C=CHPh)Pt(CN–Ad)(L) [L=PPh3 (1a), P(OPri)3 (2a)] bearing a terminal platinum-coordinated...     

Synthesis,spectral, magnetic,electrochemical and catalytic studies of cyclam-based copper(II) and nickel(II) complexes–effect of N-substitution

New N-substituted cyclam ligands 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-1,4,8,11-tetraazacyclotetradecane, 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane, 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-1,4,8,11-tetraazacyclotetradecane, and 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane (L¹–L⁴) were synthesized and mononuclear copper(II) and nickel(II) complexes prepared. The ligands and complexes were characterized by elemental analysis, electronic, IR, ¹H NMR and ¹³C NMR spectral studies. N-alkylation causes red shifts in the λ_max values of the complexes. Copper(II) complexes show one-electron, quasi-reversible reduction waves in the range ?1.04 to ?1.00 V. The nickel(II) complexes show one-electron, quasi-reversible reduction waves in the range ?1.18 to ?1.30 V and one-electron, quasi-reversible oxidation waves in the range +1.20 to +1.40 V. The reduction potential of the copper(II) and nickel(II) complexes of the ligands L¹ to L² and L³ to L⁴ shift anodically on N-alkylation. The ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry with nuclear hyperfine spin 3/2. All copper(II) complexes show a normal room temperature magnetic moment value μ_eff?=?1.70–1.74 BM which is close to the spin only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts and on the hydrolysis of 4-nitrophenylphosphate using the copper(II) and nickel(II) complexes as catalyst were carried out. The tetra-N-substituted complexes have higher rate constants than the corresponding disubstituted complexes.     

Synthesis,spectroscopic characterization and in vitro antitumor activities of some novel mononuclear Ru(Ⅱ) complexes

The synthesis and spectroscopic characterization of ruthenium complexes（R-l to R-8） of the type[Ru（A）₂（B）],(where A = 1,10-phenanthroline/2,2′-bipyridine and B = 3.4.5-tri-OCH₃DPC,4-CH₃-DPC,4-N-（CH₃）₂-DPC,4-NO₂-DPC arc described. These ligands form bidentate octahedral ruthenium complexes.The title complexes were subjected to in vitro cytotoxic activity measurements against the human cancer T-lymphocyte cell lines MTT assay.In vitro evaluation of these ruthenium complexes revealed cytotoxic activity from 0.24 to 1.4μg/mL against CEM,0.44 to 1.9μg/mL against Molt4/C8.0.28 to 1.5μg/mL against L1210,0.24 to 0.98μg/mL against HL60,and 0.25 to 1.2μg/mL against BEL7402,depending the nature of the compound.     

Synthesis,spectroscopic and X-ray structural studies of silver(I) complexes of α-keto stabilized phosphorus ylides

Reactions between AgX (X = OTf, NO₃) and ylides of the type Ph₃P = CHC(O)C₆H₄-4-R (R = F, Br, OMe) in molar ratio 1 : 2 lead to complexes [Ag{CH(PPh₃)C(O)C₆H₄-4-R}]X (1–4); X-ray structure determinations have been carried out on 4. The IR and NMR data of the products formed by reaction of Ag(I) with the ylides are consistent with C-bounded ylides. Analytical data indicate 1 : 2 stoichiometry between the ylide and Ag(I) in the products. The molar conductivities of these complexes are within the range for 1 : 1 electrolytes. Crystallographic data for 4 are: crystal system, triclinic; space group, P 1, a = 12.1151(4), b = 13.8989(5), c = 15.4855(5) Å, β = 102.676(3)°, V = 2477.82(15) ų, Z = 2.     

Synthesis,structure, spectroscopic,magnetic and electrochemical studies of a rare syn–anti acetate-bridged copper(II) complex

The structure, spectroscopy and electrochemical properties of a novel dinuclear copper(II) complex, [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ where phen = 1,10-phenanthroline, is reported. The crystal structure contains two independent Cu(II) ions, with different geometry around each copper center, which are bridged by an acetate anion. The acetate-bridged ligand shows a syn–anti coordination mode with a trigonal bipyramidal geometry for the Cu(1) center and a distorted square-based pyramidal geometry for the Cu(2) center. The angular structural index parameter τ for Cu(1) and Cu(2) is 0.9 and 0.33, respectively. The copper(II) atoms display a different geometry with a N₄O chromophore group and with Cu–O distances of 1.993(5)–1.996(5) Å and Cu–N distances which vary from 1.980(5) to 2.161(6) Å. The intra Cu…Cu separation is 4.9904(5) Å. The effective magnetic moment (μ_eff) of the complex was measured by the Evans method. The cyclic voltammogram of [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ shows two waves at positive potential which are assigned to the two Cu(II/I) reduction couples.     

Synthesis and host–guest complexation,photophysical and electrochemical studies on novel thiophenophanes

Synthesis of thiophene-based cyclophanes called thiophenophanes is described. The photophysical and electrochemical properties of thiophenophanes synthesised reveal that they show permanent fluorescence-sensing property, and the cyclic voltammogram reflects the ease with which the electron on the sulphur atom can be removed. Complexation studies of the thiophenophanes with TCNQ reveal the formation of 1:1 complex.     

Synthesis,crystal structure and spectroscopic characterization of new neutral and cationic (η-p-cymene)–ruthenium(II) complexes with phosphine–amide ligands

The dimeric starting material [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂ reacts with the phosphino-amides o-Ph₂P–C₆H₄CO–NH–R [R = ⁱPr (a), Ph (b), 4-MeC₆H₄ (c), 4-FC₆H₄ (d)] to give the mononuclear compounds 1a–d [RuCl(η⁶-p-cymene)(o-Ph₂P–C₆H₄–CO–NH–R)]Cl. The subsequent reaction of these complexes with KPF₆ produced the cationic species 2a–d [RuCl(η⁶-p-cymene)(o-Ph₂P–C₆H₄–CO–NH–R)][PF₆] in which phosphino-amides also act as rigid P,O-chelating ligands. The molecular structures of 2b–d were determined crystallographically. Amide deprotonation is achieved when complexes 2a–d were made react with 1 M aqueous solution of KOH, affording the corresponding neutral species 3a–d [RuCl(η⁶-p-cymene)(o-Ph₂P–C₆H₄–CO–N–R)] in which a P,N-coordination mode is suggested.     

A novel blue luminescent high-spin iron(III) complex with interlayer O–H⋯Cl bridging: Synthesis,structure and spectroscopic studies

A blue luminescent high-spin (s = 5/2) iron(III) complex, [Fe^III(HL¹)₂]Cl (2), was synthesized with the acyclic tridentate salicylaldehyde 2-pyridyl hydrazone ligand, H₂L¹ (1), and it can subsequently be deprotonated and methylated into blue luminescent iron(III) complexes, [Fe^III(L²)₂]Cl (3) and [Fe^III(MeL¹)₂]Cl (4) respectively. On excitation at 390 nm, the ligand and the complexes display fluorescence in the blue region (λ_em = 440–450 nm) of the spectrum. The association constant, (K_ass = 4.6421 × 10⁴ at 298 K) and the thermodynamic parameters for complex 2 have been determined by UV–Vis spectroscopy. The iron(III)–iron(II) reduction potentials lie near – 0.2 V versus SCE. The X-ray crystal structure of the complex, [Fe^III(HL¹)₂]Cl · H₂O (2), was determined, revealing meridional binding of the two ligands affording a cis-FeN₄O₂ geometry with alternate chlorine and water molecules at the interface of the main molecule, resulting in interesting interlayer O–H?Cl bridging.