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New Lennard-Jones parameters are presented for [Cd.sup.2+] and [Pb.sup.2+] ion-water interactions and a general methodology is described to obtain these parameters for any ion. [Cd.sup.2+] has shown a lesser diffusion coefficient when compared to [Pb.sup.2+], despite its smaller atomic radius, indicating a more persistent first coordination shell for the cadmium(II) ion.

The structural and thermodynamic studies of a partially substituted derivative, 5,11,17,23,tetra-tert-butyl[25,27-bis(hydroxy)-26,28-bis(ethylthioethoxy)]-calix(4)arene, and its neutral (1H NMR) and cation complexes in various media are reported. The thermodynamics of cation complexation involving analogous calix(4)arene derivatives in acetonitrile is used to build up a model in which the additive contribution of pendant arms is demonstrated.

The tautomeric forms of benximidazole N-oxide derivatives in solution using nuclear magnetic resonance (NMR) techniques are studied. In the gas phase, the N-hydroxy tautomer is more stable than the N-oxide, whereas in solution the stabilization of one form or the other depended on hydrogen bond formation involving the N-hydroxy/N-oxide moiety.

The synthesis and structural characterization, determined by H1 and C13 NMR, for a new tetraester calix[4] arene derivative containing mixed pendant arm in its lower rim are reported. The medium effect on the binding process of tetraester calix[4]arene for metal cations are examined to establish the sites of interaction of the ligand with the metal cation, the composition of complex formed and the strength of ligand-cation interaction in different media.

The interaction of lower rim calix940arene derivatives containing ester and ketone functional groups and bivalent cations has been investigated in various solvents. The presence of actonitrile leads to ligand's preorganization and these ligands discriminate between the various bivalent cations to the extent that a selectivity peak is found in terms of Gibbs energies when complexation data are plotted against cation solvation.

Research has been conducted on the cyclization-elimination reactions. Results indicate that these reactions have been slower with zinc(II) than with cadmium(II) and that the complexes containing either cyclized or uncyclized ligands have been isolated.

The ruthenium(II) complex, [Ru[Cl.sub.2](NO)L] (I), (L = [[(2-py).sub.2]P[C.sub.2][H.sub.4]P[O.sub.2](2-py)]-) was obtained from recrystallization of Ru[Cl.sub.3]NO(d2pype) (d2pype = [(2-py).sub.2]P[C.sub.2][H.sub.4]P[(2-py).sub.2]) in the presence of HN[O.sub.3], crystallizing in the monoclinic space group [P2.sub.1] (no. 4), with a = 8.012(4) [Angstrom], b = 14.454(4) [Angstrom], c = 9.353(3) [Angstrom], [beta] = 105.77(3)[degrees], and Z = 2. Crystals of the DMSO solvate of the complex (II) were obtained from [(C[D.sub.3]).sub.2]SO solution, crystallizing in the monoclinic space group [P2.sub.1]/c (no.14) with a = 9.7080(2) [Angstrom], b = 22.2920(5) [Angstrom], c = 11.5230(3) [Angstrom], [beta] = 92.0450(10)[degrees], and Z = 4. In both complexes, the geometry about the ruthenium atom is a distorted octahedron mainly as a result of the tridentate [P,N,O]-bonding mode of L. The v (NO) bands at 1875 [cm.sup-1] in both complexes are consistent with the linear disposition of the NO group and the Ru atom as is observed in the X-ray crystal structure (Ru-N1-O1 angle = 178.5(4)[degrees]). Key words: pyridylphosphine, nitrosyl, ruthenium complex, X-ray structure.

Research describes the reaction of methyl-phenyltin(IV) chloride with thiamine diphosphate and structural characterization of the products formed. Data indicate that an oxygen-capped cationic cluster, a methyltin(IV) derivative, exhibits coordination of thiamine diphosphate through its terminal phosphate group.

Results describe the synthesis and the structural and magnetic characterization of two new copper complexes with 1-phenyl-3,5-dimethylpyrazole along with bromine and chlorine. Data reveal that bromine and chlorine ions change compound structures and bond geometry.

A new approach is proposed for the preparation of ruthenium nitrosyl complexes featuring N-heterocyclic ligands. Characterization of the complexes were conducted through molar conductance measurements, elemental analysis, UV-visible, infrared, electron paramagnetic resonance and proton nuclear magnetic spectroscopies and electrochemical methods. The crystal structure indicates RuII-NO+ moiety exists in the nitrosyl complexes.

A crystalline thiamine-cadmium complex,(CdTCl3)2.2H2O, may be prepared from a mixture of aqueous CdCl2, alkali solution and TCl.HCl. In this compound, the Cd (II) ions are bridged by two N(1'), O(5gamma)-bound thiamines forming a cyclic, centrosymmetric dimer as a distorted trigonal bipyramid. The thiamine ligand is in F conformation having thetaT = 11 degrees and thetaP = 98.3 degrees. No detoxifying effect of thiamine was found in Sprague rats when injected with various regimes of B1 after injection with CdCl2.H2O. It has been postulated that a complex of cadmium chloride and thiamine may be passed from body.

The one-pot synthesis and characterization of fac-[Ru(NO)[Cl.sub.2]([K.sup.3][N.sup.4],[N.sup.8],[N.sup.11](1-carboxypropyl)cyclam)Cl*[H.sub.2]O by reaction of 1-carboxypropyl)cyclam ligand with RuNO[Cl.sub.3] is reported. The complex shows very singular structure, where the N atom of the cyclam ligand that holds the carboxypropyl pendant arm is not coordinated to the ruthenium center resulting in a [K.sup.3] denticity for the substituted cyclam ligand instead of the expected [K.sup.4].

The crystal and molecular structure of [Ru[(DMAP).sub.6]][Cl.sub.2].6[C.sub.3]C[H.sub.2]OH (DMAP = 4-dimethylaminopyridine) is studied by using X-ray diffraction method. The density functional theory (DFT) calculations have shown that in {[Ru.sup.II][(DMAP).sub.5]} the DMAP ligands have competed for the [pi] electron density of the ruthenium making the fragment a weaker [pi]-donor.

A mixture of pyridoxalrhodanine, triethylphosphinegold(I) chloride and sodium methoxide in methanol has afforded the azacoumarin complex and it is characterized by X-ray diffractometry. The results have indicated that the complex has displayed in vitro antitumor activity than cisplatin against the cisplatin-resistant cell line A2780cis.

The synthesis of the new thiamine diphosphate derivative [SnMe2(HTDP)(H2O)]Cl.H2O, its structures in solid state and in water, and the results of the kinetic experiments are described. The resulting SnMe2-holoen-zyme retains a significant proportion of the catalytic activity of the native enzyme despite the methyl groups on the metal atom.

Research has been conducted on PbPh (sub)2 Cl (sub)2. The authors have investigated the reactions of this complex with such compounds as acetophenone and salilyladehyde, and have presented the results.