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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.

A resorcarene derivative designed with pendant arms having sulfur donor atoms namely 5,11,17, -23-ethylthiomethylated calix[4] resorcarene is described. Electrical conductance provided key information regarding the composition of metal-ion complexes and their decomposition.

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.

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.