Badar Taqui Khan

Synthesis, antimicrobial, and antitumor activity of a series of palladium(II) mixed ligand complexes

Mixed ligand complexes of cisdichloromethioninepalladium(II) with 2-mercaptopyrimidine and 2-aminopyrimidine were synthesized and characterized by elemental analysis, conductivity data, infrared, and 1H NMR and 13C NMR spectra. In these mixed ligand complexes methionine coordinates to palladium through amino nitrogen and sulphur, thus leaving a free carboxylic acid group. The pyrimidine ligand coordinates to metal ion through N3. Mixed ligand complexes of cisdichloroethioninepalladium(II) with cytosine and guanosine were synthesized and characterized earlier. All the above mixed ligand complexes were screened for antimicrobial activity against Vibrio parahaemolyticus, Pseudomonas aeruginosa, Proteus vulgaris, Escherichia coli, Shigella flexnerri, Salmonella typhii, Klebsella pneumoniae, and Vibrio cholerae. It was found that complexes [Pd(meth)Cl2]: [Pd(meth)(2merpy)Cl]Cl; [Pd(meth)(2ampy)Cl]Cl; [Pd(ethio)Cl2]; [Pd(ethio)(cyt)Cl]Cl; and [Pd(ethio)(guo)Cl]Cl showed broad spectrum antimicrobial activity against all the human pathogens tested, however [Pd(meth)(2merpy)Cl]Cl eliminated plasmid with 100% frequency. These complexes have also been screened in vitro for antitumor activity against Hela (Epidermoid Carcinoma Cervix) and CHO cell lines. An excellent correlation between the antitumor activity of Pd(II) complexes and their ability to cure plasmids exists.

Homogeneous hydrogenation of cyclohexene catalyzed by complexes of rhodium and iridium

Abstract The synthesis and characterization of RhClHN(CH2CH2PPh2)2 and IrClHN(CH2CH2PPh2)2 and their catalytic activity in the homogeneous hydrogenation of cyclohexene over the temperature range 20 – 50 °C and 0.4 – 1 atm H2 partial pressure have been investigated. The dependence of the rate of hydrogenation on factors such as the catalyst concentration, the substrate concentration, H2 pressure and the temperature is reported. A mechanism has been proposed in which the catalysts activate molecular hydrogen by forming dihydrido species of the type MClL(H)2 [M = Rh(I), Ir(I) and L = HN(CH2CH2PPh2)2] followed by transfer of hydrogen to the olefin to form the saturated product. The experimental data are in accordance with a rate expression of the form : Rate = where [H2], [S] and [C] are the concentration of H2, substrate and catalyst, respectively. The activation parameters of the reaction, ΔH‡ and ΔS‡, have also been evaluated.

Crystal and molecular structure of cis-dichloroethionineplatinum(II) and its interaction with adenine, hypoxanthine, cytosine and their nucleosides

Abstract The crystal and molecular structure of patent compound cis -dichloroethionineplatinum(II) was determined by X-ray diffraction method. The complex crystallises with 4 molecules in the monoclinic space group P 2 1 /n with a cell of dimensions a = 7.223(1), b = 14.435(1), c = 11.012(2) A, β=97.69(2)°. The structure was solved by the heavy atom method and has been refined to an R value of 0.031 for 1573 observed reflections. In cis -dichloroethionineplatinum(II), the ethionine molecule coordinates to the platinum through the amino nitrogen and sulfur atoms to form a six-membered ring which adopts a skewed chair conformation. The predominant force of packing in this complex is the intermolecular hydrogen bonding between the two free carboxylic acid groups of adjacent molecules of ethionine. These are reinforced by weak NH…Cl bonds to stabilise crystal packing. Mixed ligand complexes of Pt(II)ethionine with adenine, adenosine, hypoxanthine, ionosine, cytosine and cytidine were synthesised and characterised by elemental analysis, conductivity measurements, IR and 1 H NMR spectral studies. In the complexes of adenine, adenosine, hypoxanthine and ionosine the ligand binding site to the metal ion is N 7 , whereas in the case of cytosine and cytidine the binding site is N 3 .

Mixed ligand complexes of cis-dichloroethionine palladium(II) with purines, pyrimidines and nucleosides

Abstract Mixed ligand complexes of cis-dichloroethionine palladium(II) with adenine, adenosine, guanine, guanosine, hypoxanthine, inosine, cytosine and cytidine were synthesised and characterised by elemental analysis, conductivity data, IR and 1H NMR spectral studies. In all these mixed ligand complexes the ethionine molecule coordinates to the palladium through the amino nitrogen and sulphur atoms, thus leaving a free carboxylic acid group. In the complexes of purines and their corresponding nucleosides, the ligand binding site to the metal ion is N7, whereas in the case of pyrimidine and their corresponding nucleosides it is N3.

Thermodynamics of the hydrogenation of olefins catalyzed by Rh(I) and Ir(I) complexes

Abstract The homogeneous hydrogenation of cyclohexene catalyzed by Rh(I) and Ir(I) complexes of the terdentate ligands (L) HN(CH2CH2Aφ2)2 (A = P, As) was investigated in the temperature range 20 - 50°C. Thermodynamic parameters corresponding to the formation of the dihydrido complexes ML(H)2Cl (M = Ir(I), Rh(I)) and the olefin complexes MLCl(olefin) were computed. The activation parameters corresponding to the rate constant were also calculated. An inverse relationship is found between the enthalpy of formation ΔH0 of the dihydrido complexes and the enthalpy of activation ΔH≠ of the hydrogenation step. This relationship establishes the involvement of the dihydrido complexes as the active intermediates in olefin coordination and hydrogen transfer. The stereochemistry of the terdentate complexes in dihydride formation is discussed. It is concluded that the enthalpy of formation ΔH0 of the dihydrido complexes of terdentate ligands is very favourable, as there is no change in the configuration of the ligand in oxidative addition reaction. The significance of the steric factors in the hydrogenation step is discussed.

MIXED LIGAND COMPLEXES OF PLATINUM(II) WITH α-AMINO ACIDS AND PURINES AND PYRIMIDINES

Abstract The synthesis and characterization of mixed ligand complexes of platinum(II) with amino acids as primary ligands and purine and pyrimidine bases as secondary ligands are reported. The interaction of platinum(II) glycine and alanine complexes with purine and pyrimidine, carried out in a 1 : 1 ratio resulted in the formation of mixed ligand complexes. In these complexes adenine and guanine are coordinated to the metal ion through N(7) whereas hypoxanthine acts as a bridging ligand coordinating through N(3) and N(9). The pyrimidines are coordinated to the metal ion through N(3). In all the mixed ligand complexes the amino acids behave as monodentate ligands coordinating through amino nitrogen.

Interaction of platinum(II) amino acid complexes with nucleosides

We report the synthesis of mixed ligand complexes of platinum(II) with glycine or alanine as primary ligands and the nucleosides adenosine, guanosine, inosine, cytidine and uridine as secondary ligands. Interaction of platinum(II) amino acid complexes with nucleosides was carried out in a 1:1 ratio, resulting in the formation of cis dichloro complexes. It was found that adenosine and guanosine coordinate to the metal ion through N(7), whereas inosine binds through N(1). The pyrimidine nucleosides coordinate to the metal ion through N3. In these complexes the amino acid behaves as a monodentate ligand coordinating through the amino nitrogen. These complexes are insoluble in aqueous medium but on addition of base they become soluble due to the neutralization of the proton located on the carboxylic group of the amino acid.

Binary and Ternary Metal Complexes of Uridine and Thermodynamic Quantities Associated with the Interaction of Uridine with Bivalent Metal ions in Solution

Abstract Formation of binary and ternary complexes of Cu(II), Ni(II), Zn(II), Co(II), Mn(II), Mg(II), Ca(II), metal ions with uridine as a primary ligand and 2,2′-bipyridyl, 1,10-phenanthroline and 5-sulphosalicylic acid as secondary ligands was studied by a potentiometric technique at 15°, 25°, 35° and 45°C and 0.10 M (KNO3) ionic strength. The ternary complex formation was found to take place in a stepwise manner. The stability constants of these binary and ternary systems were calculated and the Δ log K values obtained were found to be negative. The lower stability of 1:2 complexes of uridine and those of the ternary systems compared to the corresponding binary systems is in accord with statistical considerations. Thermodynamic parameters are reported for all the systems studied.

Mixed ligand complexes of ruthenium(III)edta with pyrimidines

Abstract Mixed ligand complexes of ruthenium(III)edta with cytosine, uracil, 2-thiocytosine, 2-aminopyrimidine and 5-aminouracil were synthesised and characterised by elemental analysis, conductivity, infrared spectra, electronic spectra, 1 H NMR, ESR and polarography. Uracil acts as a monodentate ligand coordinating to the metal ion through C 2 O. The ligands cytosine, 2-thiocytosine, 2-aminopyrimidine, 5- aminouracil act as bidentate ligands coordinating to the metal ion through N 3 and C 2 O; N 3 and C 2 SH; N 3 and C 2 NH 2 ; C 6 and 5NH 2 , respectively. 5-Aminouracil forms an interesting organometallic complex. In this complex the C 6 carbon of 5-aminouracil forms a covalent bond with ruthenium(III), with simultaneous coordination of the nitrogen of the exocyclic amino group to a second ruthenium atom forming a 2:2 diligand bridged bimetallic complex.

Complexes of Pt(II) and Pt(IV) with disubstituted purines

Abstract Mixed-ligand complexes of Pt(II) and Pt(IV) with 2,6-diaminopurine and 6-thioguanine were synthesized and characterised. The complexes were prepared in acidic and basic media. The binding of the ligands to the metal ion varies according to the pH of the medium. Thus, in the complexes of 6-thioguanine, the ligand acts as a monodentate ligand coordinating through the neutral C 6 -SH group in the acidic medium and in the basic medium as a bidentate ligand binding to the metal ion through C 6 S − and N 7 , forming a five-membered chelate ring. In an acidic medium 2,6-diaminopurine forms mononuclear complexes with Pt(II) and Pt(IV) binding through N 7 . In a basic medium binuclear hydroxobridged complexes are formed with Pt(IV) and the ligand is monodentate, coordinating through N 7 .