Characterization and biological studies of a new platinum(II) complex with the amino acid L-alliin

Synthesis and characterization of a new Pt(II) complex with the amino acid L-alliin (S-allyl-L-cysteine sulfoxide, C₆H₁₁NO₃S) are described. Elemental and mass spectrometric analyses of the solid complex are consistent with [PtCl₂(alliin)], or [PtCl₂(C₆H₁₁NO₃S)]. ¹³C nuclear magnetic resonance (NMR), [¹H–¹⁵N] two dimensional (2D) NMR and infrared spectroscopy indicate coordination of the ligand to Pt(II) through the N and S atoms. The complex is very soluble in dimethyl sulfoxide. Biological analysis for evaluation of a potential cytotoxic effect of the complex was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented moderate cytotoxic activity, inducing about 40% cell death at a concentration of 400 μmol ·?L^?1.     

Synthesis, characterization and antimicrobial activity of palladium(II) complexes with some alkyl derivates of thiosalicylic acids: Crystal structure of the bis(S-benzyl-thiosalicylate)-palladium(II) complex, [Pd(S-bz-thiosal)2]

S-Alkyl (R = benzyl, methyl, ethyl, propyl and butyl) derivatives of thiosalicylic acid and the corresponding palladium(II) complexes were prepared and their structures were proposed on the basis of infrared, ¹H and ¹³C NMR spectroscopy. The cis geometrical configurations of the isolated complexes were proposed on the basis of an X-ray structural study of the bis(S-benzyl-thiosalicylate)-palladium(II), [Pd(S-bz-thiosal)₂] complex.Antimicrobial activity of the tested compounds was evaluated by determining the minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) in relation to 26 species of microorganisms. The tested ligands, with a few exceptions, show low antimicrobial activity. The palladium(II) complexes, [Pd(S-R-thiosal)₂], have statistically significant higher activity than the corresponding ligands. The complexes [Pd(S-et-thiosal)₂] and [Pd(S-pro-thiosal)₂] displayed the strongest activity amongst the all tested compounds. The palladium(II) complexes show selective and moderate antibacterial activity and significant antifungal activity. The most sensitive were Aspergillus fumigatus and Aspergillus flavus.     

Solution structure of the palladium(II) complex of 1,4,7,10-tetrathiacyclododec-2-ene-2,3-dicarbonitrile

The solution structure of the Pd(II) complex of mn-12-S4 was studied in detail by NMR spectroscopy. The stoichiometry of the complex was determined by 1H NMR titration experiments. 3J(H,H) coupling constants were extracted from the 2D J-resolved NMR spectrum of the complex providing information concerning the S-C-C-S torsional angles. Further conclusions about the conformation of [Pd(mn-12-S4)](BF4)2 were drawn from experimental NOEs. The results of the NMR study were corroborated by molecular modelling.     

Ruthenium(II) and palladium(II) complexes with 2,6-(bispyrazol-1-yl)pyridines

Ruthenium(II) and palladium(II) complexes [Ru(DMSO)(L)Cl₂] and [Pd(L)Cl]Cl, where L = 2,6-bis(pyrazol-1-yl)pyridine (bpp) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (bdmpp) have been synthesized. All complexes were characterized by elemental analysis, IR, ¹H NMR, UV-Vis, and cyclic voltammetry measurements.     

Synthesis,characterization and initial biological studies of a new platinum(II) complex with deoxyalliin

A new platinum(II) complex with deoxyalliin was synthesized and characterized by chemical and spectroscopic techniques. Elemental and mass spectrometry analyses of the solid complex fit to the composition [Pt(C₆H₁₁NO₂S)Cl₂]·H₂O. ¹³C NMR, ¹⁵N NMR and infrared spectra of the complex are consistent with coordination of deoxyalliin to Pt(II) through the nitrogen and sulfur atoms forming a square-planar geometry. The complex is soluble in dimethylsulfoxide. Biological analysis for evaluation of a potential cytotoxic effect of the complex was performed using HeLa cells, a human cervix adenocarcinoma-derived cell line. The results were compared with those of a palladium(II) complex previously described.     

Synthesis, structural characterization, antimicrobial and cytotoxic effects of aziridine, 2-aminoethylaziridine and azirine complexes of copper(II) and palladium(II)

The synthesis, spectroscopic and X-ray structural characterization of copper(II) and palladium(II) complexes with aziridine ligands as 2-dimethylaziridine HNCH(2)CMe(2) (a), the bidentate N-(2-aminoethyl)aziridines C(2)H(4)NC(2)H(4)NH(2) (b) or CH(2)CMe(2)NCH(2)CMe(2)NH(2) (c) as well as the unsaturated azirine NCH(2)CPh (d) are reported. Cleavage of the cyclometallated Pd(II) dimer [μ-Cl(C(6)H(4)CHMeNMe(2)-C,N)Pd](2) with ligand a yielded compound [Cl(NHCH(2)CMe(2))(C(6)H(4)CHMe(2)NMe(2)-C,N)Pd] (1a). The reaction of the aziridine complex trans-[Cl(2)Pd(HNC(2)H(4))(2)] with an excess of aziridine in the presence of AgOTf gave the ionic chelate complex trans-[(C(2)H(4)NC(2)H(4)NH(2)-N,N')(2)Pd](OTf)(2) (2b) which contains the new ligand b formed by an unexpected insertion and ring opening reaction of two aziridines ("aziridine dimerization"). CuCl(2) reacted in pure HNC(2)H(4) or HNCH(2)CMe(2) (b) again by "dimerization" to give the tris-chelated ionic complex [Cu(C(2)H(4)NC(2)H(4)NH(2)-N,N')(3)]Cl(2) (3b) or the bis-chelated complex [CuCl(C(2)H(2)Me(2)NC(2)H(2)Me(2)NH(2)-N,N')(2)]Cl (4c). By addition of 2H-3-phenylazirine (d) to PdCl(2), trans-[Cl(2)Pd(NCH(2)CPh)(2)] (5d) was formed. All new compounds were characterized by NMR, IR and mass spectra and also by X-ray structure analyses (except 3b). Additionally the cytotoxic effects of these complexes were examined on HL-60 and NALM-6 human leukemia cells and melanoma WM-115 cells. The antimicrobial activity was also determined. The growth of Gram-positive bacterial strains (S. aureus, S. epidermidis, E. faecalis) was inhibited by almost all tested complexes at the concentrations of 37.5-300.0 μg mL(-1). However, MIC values of complexes obtained for Gram-negative E. coli and P. aeruginosa, as well as for C. albicans yeast, mostly exceeded 300 μg mL(-1). The highest antibacterial activity was achieved by complexes 1a and 2b. Complex 2b also inhibited the growth of Gram-negative bacteria.     

Synthesis and characterisation of macrocyclic palladium(II)-sodium(I) complexes: generation of an unusual metal-mediated electron delocalisation

Reaction of sodium perchlorate-crown ether derivative (LH2) complex [Na2LH2](ClO4)2 (1) with palladium acetate afforded two related compounds of macrocyclic palladium(II)-sodium(I) dimeric tetranuclear complexes, [Pd2Na2L2(mu-OH2)2](ClO4)2(CH2Cl2)3 (2) and [Pd2Na2(L-)2](CH3CN)2(C3H6O)2 (3) and their structures were characterised by IR, NMR, mass and X-ray analysis; the latter was revealed as an unusual metal-mediated electron delocalised complex.     

Stoichiometric reactions of methylparathion with a palladium aryl oxime metallacycle

The reaction of [Pd(3)(OAc)(6)] with (E)-acetophenone oxime and pyridine in CHCl(3) under reflux affords the metallacycle [Pd(OAc)[C,N-(C(6)H(4)C(CH(3))=NOH)-2](py)] (1) as a yellow air-stable complex. The same reaction carried out at room temperature in the absence of pyridine affords the trinuclear oximato complex [Pd(mu-(E)-ON=C(CH(3))Ph)(mu-OAc)](3) (2), which can be converted into 1 upon heating in the presence of pyridine. As indicated by (1)H and (31)P NMR spectroscopy, complex 1 reacts with methylparathion in acetone-d(6)-D(2)O solutions to afford [Pd(SP(=O)(OCH(3))(2))[C,N-(C(6)H(4)C(CH(3))=NOH)-2](py)] (3) and [Pd(mu-SP(=O)(OCH(3))(2))[C,N-(C(6)H(4)C(CH(3))=NOH)-2]](2) (4) as well as free p-nitrophenol. Compounds 1-4 have been characterized by single-crystal X-ray analysis, NMR and EA. Compounds 1 and 3 are mononuclear complexes with the acetate and dimethylthiophosphate ligand, respectively, trans from the phenyl group. Compound 2 is a trinuclear complex whose structure can be derived from that of [Pd(3)(OAc)(6)] by replacing three of the acetate ligands on one side of Pd(3) plane by three N,O-coordinated oximate ligands. Complex 4 is a dinuclear complex in which the two square-planar palladium moieties are linked by the sulfur atoms of the bridging dimethylthiophosphate ligands.     

Spectroscopic, kinetic, and mechanistic study of a new mode of coordination of indole derivatives to platinum(II) and palladium(II) ions in complexes

Binding of tryptophan residue to intrinsic metal ions in proteins is unknown, and very little is known about the coordinating abilities of indole. Indole-3-acetamide displaces the solvent ligands from cis-[Pt(en)(sol)2]2+, in which sol is acetone or H2O, in acetone solution and forms the complex cis-[Pt(en)(indole-3-acetamide)]2+ (3) of spiro structure, in which the new bidentate ligand coordinates to the Pt(II) atom via the C(3) atom of the indolyl group and the amide oxygen atom. This structure is supported by 1H, 13C, 15N, and 195Pt NMR spectra and by UV, IR, and mass spectra. Molecular mechanical simulations by Hyperchem and CHARMM methods give consistent structural models; the latter is optimized by density-functional quantum chemical calculations. Dipeptide-like molecules N-(3-indolylacetyl)-L-amino acid in which amino acid is alanine, leucine, isoleucine, valine, aspartic acid, or phenylalanine also displace the solvent ligands in acetone solution and form complexes cis-[Pt(en) N-(3-indolylacetyl)-L-amino acid)]2+ (6), which structurally resemble 3 but exist as two diastereomers, detected by 1H NMR spectroscopy. The bulkier the amino acid moiety, the slower the coordination of these dipeptide-like ligands to the Pt(II) atom. The indolyl group does not coordinate as a unidentate ligand; a second donor atom is necessary for bidentate coordination of this atom and the indolyl C(3) atom. The solvent-displacement reaction is of first and zeroth orders with respect to indole-3-acetamide and cis-[Pt(en)(sol)2]2+, respectively. A mechanism consisting of initial unidentate coordination of the ligand via the amide oxygen atom followed by closing of the spiro ring is supported by 1H NMR data, the kinetic effects of acid and water, and the activation parameters for the displacement reaction. In the case of N-(3-indolylacetyl)-L-phenylalanine, the bulkiest of the entering ligands, the reaction is of first order with respect to both reactants. The bidentate indole-3-acetamide ligand in 3 is readily displaced by (CH3)2SO and 2-methylimidazole, but not by CNO-, CH3COO-, and CH3CN. Complexes cis-[Pd(en)(sol)2]2+ and cis-[Pd(dtco)(sol)2]2+ react with indole-3-acetamide more rapidly than their Pt(II) analogues do and yield complexes similar to 3. This study augments our recent discovery of selective, hydrolytic cleavage of tryptophan-containing peptides by Pd(II) and Pt(II) complexes.     

Covalent and noncovalent interactions for [metal(dien)nucleobase](2+) complexes with L-tryptophan derivatives: formation of palladium-tryptophan species by nucleobase substitution under biologically relevant conditions

The interaction of the complexes [Pd(dien)(1-MeCyt)]2+ (2) and [Pd(dien)(9-EtGH)]2+ (3) with the amino acids L-tryptophan (Trp) and N-acetyltryptophan (N-AcTrp) was studied and compared with the previously studied platinum analogues [Pt(dien)(1-MeCyt)]2+ (4) and [Pt(dien)(9-EtGH)]2+ (5). Solid-state structures for 2 and 4 are reported. For the palladium complexes, the interaction is pH sensitive. Below pH 5, the noncovalent interaction with stacking between the aromatic amino acid residue and the metalated nucleobase was observed. Fluorescence quenching experiments indicated similar association constants for platinum and palladium derivatives 2-5. Unusual substitution of the model nucleobases 1-methylcytosine (1-MeCyt) and 9-ethylguanine (9-EtGH) by tryptophan was observed in the range of pH 5-11. The resulting species [Pd(dien)(Trp)]+ (6) and [Pd(dien)(N-AcTrp)]+ (7) were characterized using 1H NMR, 13C NMR, and ESI-MS spectroscopy with coordination indicated through the amino and deprotonated amido nitrogens, respectively. Complexes 6 and 7 were also obtained from a solution of [Pd(dien)Cl]+ (1) incubated with either Trp or N-AcTrp, respectively.     

Redox-active p-quinone-based Bis(pyrazol-1-yl)methane ligands: synthesis and coordination behaviour

The synthesis, structural characterisation and coordination behaviour of mono- and ditopic p-hydroquinone-based bis(pyrazol-1-yl)methane ligands is described (i.e., 2-(pz2CH)C6H3(OH)2 (2a), 2-(pz2CH)-6-(tBu)C6H2(OH)2 (2b), 2-(pz2CH)-6-(tBu)C6H2(OSiiPr3)(OH) (2c), 2,5-(pz2CH)2C6H2(OH)2 (4)). Ligands 2a, 2b and 4 can be oxidised to their p-benzoquinone state on a preparative scale (2a ox, 2b ox, 4 ox). An octahedral Ni II complex [trans-Ni(2c)2] and square-planar Pd II complexes [Pd2bCl2] and [Pd2b ox Cl2] have been prepared. In the two Pd II species, the ligands are coordinated only through their pyrazolyl rings. The fact that [Pd2bC12] and [Pd2b oxC12] are isolable compounds proves that redox transitions involving the p-quinone substituent are fully reversible. In [Pd2b oxCl2], the methine proton is highly acidic and can be abstracted with bases as weak as NEt(3). The resulting anion dimerises to give a dinuclear macrocyclic Pd II complex, which has been structurally characterised. The methylated ligand 2-(pz2CMe)C6H3O2 (11 ox) and its Pd II complex [Pd11 oxCl2] are base-stable. A new class of redox-active ligands is now available with the potential for applications both in catalysis and in materials science.     

Synthesis,characterization, and insecticidal activity of new tin (IV) complexes

A three-component reaction of dimethyltin dibromide with imidazo[1,2-a]pyridine, pyridine derivatives, or isoquinoline and allyl bromide in refluxing ethanol affords the ionic complex, bis(1-allylcycloiminium) dimethyltetrabromostannate (II). The reaction involves N-allylation of cycloimine accompanied by the coordination of two bromide ions with the tin atom of dimethyltin dibromide. The complexes have been characterized by infrared and ¹H NMR, ¹³C NMR, and ¹¹⁹Sn NMR studies. The X-ray crystal structure analysis of a complex reveals the tin atom to be hexacoordinated and the dimethyltetrabromostannate (II) anion having octahedral geometry. Some of the complexes tested for their insecticidal activity are found to exhibit strong activity against Tribolium castaneum insect with LC₅₀ ranging from 0.4 to 0.8 ppm.     

Synergic effect of two metal centers in catalytic hydrolysis of methionine-containing peptides promoted by dinuclear palladium(II) hexaazacyclooctadecane complex

The species obtained by the reaction of [Pd2([18]aneN6)Cl2](ClO4)2(where [18]aneN6 is 1,4,7,10,13,16-hexaazacyclooctadecane) with AgBF4 have been determined by electrospray ionization mass spectrometry (ESI-MS) to be an equilibrium mixture of three major types of dinuclear Pd(II) complex cations, [Pd2(mu-O)([18]aneN6)]2+, [Pd2(mu-OH)([18]aneN6)]3+ and [Pd2(H2O)(OH)([18]aneN6)](3+), in aqueous solution. The hydroxo-group-bridged one, [Pd2(mu-OH)([18]aneN6)]3+, is a dominant species, whose crystal structure has been obtained. The crystal structure of [Pd2(mu-OH)([18]aneN6)](ClO4)3 shows that each Pd(II) ion in the dinuclear complex is tetra-coordinated by three nitrogen atoms and one hydroxo group bridge in a distorted square configuration. The two Pd(II) ions are 3.09 A apart from each other. The dinuclear Pd(II) complex cations [Pd2(mu-OH)([18]aneN6)]3+ and [Pd2(H2O)(OH)([18]aneN6)]3+ can efficiently catalyze hydrolysis of the amide bond involving the carbonyl group of methionine in methionine-containing peptides with turnover number of larger than 20. In these hydrolytic reactions, the two Pd(II) ions are synergic; one Pd(II) ion anchors to the side chain of methionine and the other one delivers hydroxo group or aqua ligand to carbonyl carbon of methionine, or acts as a Lewis acid to activate the carbonyl group of methionine, resulting in cleavage of Met-X bond. The binding constant of dinuclear Pd(II) complex cations with AcMet-Gly and AcMet were determined by 1H NMR titration to be 282 +/- 2 M(-1) and 366 +/- 4 M(-1), respectively. The relatively low binding constants enable the catalytic cycle and the possible catalytic mechanism is proposed. This is the first artificial mimic of metallopeptidases with two metal active centers.     

[Pd(H)(SnCl3)L2]: The key active species in the catalyzed alkoxycarbonylation reaction of terminal alkenes

The four complexes [Pd(H)(Cl)L₂] and [Pd(H)(SnCl₃)L₂], L = PPh₃, PCy₃, have been synthesized and fully characterized by multinuclear NMR. They represent the active species of the hydride palladium-catalyzed alkoxycarbonylation of terminal alkenes. Isolation of the model acylplatinum complex, resulting from the carbonylation of dihydromyrcene, clearly shows that SnCl₂ as co-catalyst produces a SnCl₃ ligand which modulates the metal center electron density.     

Palladium(II) complexes of unsymmetrical CNN pincer ligands

Unsymmetrical 1-(arylimino)-3-(2-hetarylimino)isoindolines have been prepared from 1,3-diiminoisoindoline, an arylamine (aniline, 2-methylaniline, 2-iodoaniline), and a heteroaromatic amine (2-amino-6-methylpyridine, 2-amino-4-methylthiazole) in a stepwise manner by two consecutive condensations. The metalation reactions of these compounds with palladium(II) acetate proceed upon cyclopalladation of the carbocyclic aryl moieties and yield unsymmetrical C, N, N pincer complexes in all cases. X-ray crystallographic analysis were performed on single crystals of hydrogen{acetato[1-phenylimino-3-(6-methylpyridylimino)isoindolinato]palladate(II)} H[(phpi)Pd(OAc)] and pyridine[1-(2-tolylimino)-3-(4-methylthiazolylimino)isoindolinato]palladium(II) [(2-tolti)Pd(py)] by which the coordination mode, the conformation, the protonation site, and the trans influence of the carbon donor were established. For one more C, N, N pincer complex, hydrogen{acetato[1-(2-iodophenylimino)-3-(6-methylpyridylimino)isoindolinato]palladate(II)} H[(2-Iphpi)Pd(OAc)], a similar mononuclear coordination mode was confirmed by (1)H NMR spectroscopy, whereas for the product of an oxidative addition reaction of a palladium(0) precursor to the iodoaryl derivative a product with exo coordination was found. First experiments showed the effectivity of one of these complexes as a precatalyst in CC coupling reactions (Heck and Stille coupling).     

Butylene linked palladium N-heterocyclic carbene complexes: Synthesis and catalytic properties

New bis(NHC)-Pd complexes were synthesized and characterized by elemental analysis, ¹H NMR, ¹³C NMR, and IR spectroscopy. The reaction of Pd(OAc)₂ and bis(benzimidazolium) salts in DMSO gave the monomeric palladium complex in which the N-heterocyclic carbene was bound to the metal centre. The crystal and molecular structure of the cis-dibromo{1,1′-di[2,3,4,5,6-pentamethylbenzyl]-3,3′-butylenedibenzimidazol-2,2′-diylidene}-palladium(II) complex was determined by single-crystal X-ray diffraction. The activity of the Pd(II) complexes in the direct arylation of benzothiazole with arylbromides was investigated. A preliminary catalytic study showed that these bis(NHC)-Pd complexes were highly active in the direct arylation of benzothiazole with arylbromides.     

Palladium(II) complexes, as synthetic peptidases, regioselectively cleave the second peptide bond "upstream" from methionine and histidine side chains

Palladium(II) complexes promote hydrolysis of natural and synthetic oligopeptides with unprecedented regioselectivity; the only cleavage site is the second peptide bond upstream from a methionine or a histidine side chain, that is, the bond involving the amino group of the residue that precedes this side chain. We investigate this regioselectivity with four N-acetylated peptides as substrates: neurotransmitter methionine enkephalin (Ac-Tyr-Gly-Gly-Phe-Met) and synthetic peptides termed Met-peptide (Ac-Ala-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala), His-peptide (Ac-Val-Lys-Gly-Gly-His-Ala-Lys-Tyr-Gly-Gly-Met(OX)-Ala-Ala-Arg-Ala), in which a Met is oxidized to sulfone, and HisMet-peptide (Ac-Val-Lys-Gly-Gly-His-Ala-Lys-Tyr-Gly-Gly-Met-Ala-Ala-Arg-Ala). While maintaining protein-like properties, these substrates are suitable for quantitative study since their coordination to Pd(II) ion can be determined (by NMR spectroscopy), and the cleavage fragments can be separated (by HPLC methods) and identified (by MALDI mass spectrometry). The only peptide bonds cleaved were the Gly3-Phe4 bond in methionine enkephalin, Gly4-Gly5 bond in Met-peptide, Gly3-Gly4 in His-peptide, and Gly3-Gly4 and Gly9-Gly10 bonds in HisMet-peptide. We explain this consistent regioselectivity of cleavage by studying the modes of Met-peptide coordination to the Pd(II) ion in [Pd(H(2)O)(4)](2+) complex. In acidic solution, the rapid attachment of the Pd(II) complex to the methionine side chain is followed by the interaction of the Pd(II) ion with the peptide backbone upstream from the anchor. In the hydrolytically active complex, Met-peptide is coordinated to Pd(II) ion as a bidentate ligand - via sulfur atom in the methionine side chain and the first peptide nitrogen upstream from this anchor - so that the Pd(II) complex approaches the scissile peptide bond. Because the increased acidity favors this hydrolytically active complex, the rate of cleavage guided by either histidine or methionine anchor increased as pH was lowered from 4.5 to 0.5. The unwanted additional cleavage of the first peptide bond upstream from the anchor is suppressed if pH is kept above 1.2. Four Pd(II) complexes cleave Met-peptide with the same regioselectivity but at somewhat different rates. Complexes in which Pd(II) ion carries labile ligands, such as [Pd(H(2)O)(4)](2+) and [Pd(NH(3))(4)](2+), are more reactive than those containing anionic ligands, such as [PdCl(4)](2)(-), or a bidentate ligand, such as cis-[Pd(en)(H(2)O)(2)](2+). When both methionine and histidine residues are present in the same substrate, as in HisMet-peptide, 1 molar equivalent of the Pd(II) complex distributes itself evenly at both anchors and provides partial cleavage, whereas 2 molar equivalents of the promoter completely cleave the second peptide bond upstream from each of the anchors. The results of this study bode well for growing use of palladium(II) reagents in biochemical and bioanalytical practice.     

Platinum and palladium complexes of thiosemicarbazones derived of 2-acetylthiophene: Synthesis and spectral studies

The reaction of 2-acetylthiophene thiosemicarbazone (2-HATT) and 2-acetylthiophene 4-phenylthiosemicarbazone (2-HAT-4-FT) with Pd(COD)Cl(2) (COD = 1,5-cyclooctadiene) and trans-Pt(2)PEt(3)Cl(4) yielded four new metal complexes: [Pd(2-HATT)Cl(2)] (1), [Pd(2-ATT)(2)] (2), [Pd(2-AT-4-FT)Cl] (3) and [Pt(2-ATT)(PEt(3))Cl] (4). Apart from compound 3 all the others were characterised by (1)H and (13)C{(1)H} NMR, infrared spectroscopy, and elemental analysis. Multinuclear NMR experiments of (31)P{(1)H} and (195)Pt{(1)H} of complex 4 have revealed that the ligand 2-HATT behaves as a bidentate chelating agent towards Pd(COD)Cl(2) and trans-Pt(2)PEt(3)Cl(4) whereas ligand 2-HAT-4-FT forms a tridentate chelating complex with Pd(COD)Cl(2).     

Synthesis, characterization of Ag(I), Pd(II) and Pt(II) complexes of a triazine-3-thione and their interactions with bovine serum albumin

Ag(I), Pd(II) and Pt(II) complexes of 5-methoxy-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione (LH(2)OCH(3)) have been synthesized and characterized by elemental analysis, molar conductance, (1)H NMR, IR spectra, UV spectra and thermal analysis (TG-DTA). The components of the three complexes are [Ag(C(15)H(10)N(3)S)](6), Pd(C(15)H(10)N(3)S)(2) and Pt(C(15)H(10)N(3)S)(2).C(3)H(6)O.2H(2)O, respectively. All the complexes are nonelectrolyte and have high thermodynamic stability. The ligand may act as bidentate NS donor for Pd(II) and Pt(II) complexes, while it seems to be bidentate NS bridging via sulphur atom for Ag(I) complex. A planar quadrangular structure is proposed for Pd(II) and Pt(II) complexes and Ag(I) complex may be a hexanuclear cluster. Their interactions with bovine serum albumin (BSA) are investigated using steady state fluorescence technology. It is observed that all of them can quench the intrinsic fluorescence of BSA through static quenching procedure. The binding constants (K(A)) at different temperatures, thermodynamic parameters enthalpy changes (DeltaH) and entropy changes (DeltaS) between BSA and the compounds are calculated. Based on the values of DeltaH and DeltaS, it is judged that the main acting force of PtL(2).C(3)H(6)O.2H(2)O with BSA may be electrostatic interaction, and for the LH(2)OCH(3), Ag(6)L(6) and PdL(2), hydrophobic and electrostatic interactions may be involved in their binding processes.     

Chemical and spectroscopic studies of a new palladium(II) complex with N -acetyl-L-cysteine

Chemical and spectroscopic studies of a new palladium(II) N-acetyl-L-cysteine complex are described. Elemental analyses for the solid complex are consistent with the formula [Pd(C₅H₈NO₃S)₂]?·?H₂O or [Pd(NAC)₂]?·?H₂O. Solid-state ¹³C nuclear magnetic resonance (NMR), UV–Visible (UV–Vis) and infrared (IR) spectroscopic analyses are consistent with coordination of the ligand to palladium(II) through the nitrogen and sulfur atoms in a square-planar geometry. Thermogravimetric and differential thermal analyses confirmed the composition; final residue was identified as metallic palladium.