The relevance of cis and trans influences of some anionic ligands X and Y in cis-[PtX(2)(PPh(3))(2)] and cis-[PtXY(PPh(3))(2)] complexes have been studied by the X-ray crystal structures of several derivatives (X(2) = (AcO)(2) (3), (NO(3))(2) (5), Br(2) (7), I(2) (11); and XY = Cl(AcO) (2), Cl(NO(3)) (4), and Cl(NO(2)) (13)), density functional theory (DFT) calculations, and one bond Pt-P coupling constants, (1)J(PtP). The latter have allowed an evaluation of the relative magnitude of both influences. It is concluded that such influences act in a cooperative way and that the cis influence is not irrelevant when rationalizing the (1)J(PtP) values, as well as the experimental Pt-P bond distances. On the contrary, in the optimized geometries, evaluated through B3LYP/def2-SVP calculations, the cis influence was not observed, except for compounds ClPh (21), Ph(2) (22), and, to a lesser extent, Cl(NO(2)) (13) and (NO(2))(2) (14). A natural bond order analysis on the optimized structures, however, has shown how the cis influence can be related to the s-character of the Pt hybrid orbital involved in the Pt-P bonds and the net atomic charge on Pt. We have also found that in the X-ray structures of cis-[PtX(2)(PPh(3))(2)] complexes the two Pt-X and the two Pt-P bond lengths are different each other and are related to the conformation of the phosphine groups, rather than to the crystal packing, since this feature is observed also in the optimized geometries.

This paper presents some copper(II) complexes of salen analogues in which the two salicylaldehyde moieties carry different (electron donor, D, and acceptor, A) substituents in position 5, producing a push-pull charge asymmetry. The X-ray structures of some compounds show the presence of pairs of stacked molecules with head-to-tail intermolecular associations. The geometries of all complexes have been optimized through density functional theory (DFT) studies, which have shown that a major influence on the coordination bond lengths is given by the presence of the electron acceptor NO2 group. Such an influence operates mainly on the Cu-phenolato bonds: elongation of the Cu-O distance of the 5-nitrosalicylaldehyde moiety, with a concomitant decrease of the other Cu-O distance; the Cu-N bonds are less affected. The D groups have only a minor influence. The nonlinear optical responses, microgBetavec, of some molecules have been determined by EFISH measurements, and the Beta-vec values have been obtained using the DFT-calculated microg values because solubility problems hampered the experimental measurements of microg of some derivatives; the former, however, have been found to be in agreement with the experimental values that could be obtained. Deconvolution of the absorption bands in the near-UV region has allowed recognition of the charge-transfer (CT) transition, assigned to a ligand-to-metal CT (LMCT) by time-dependent DFT computations; we have then used the solvatochromism of this transition to obtain Beta0 and BetaCT values using the two-state model. These values were compared with those obtained by computational studies, which have also allowed evaluation of the influence of the substituents on the directions of microg and Betatot.

The clinical success of cisplatin (cis-diamminedichloroplatinum(1r)) in antitumor chemotherapy has encouraged an all-out search for analogues with lower toxicity, improved therapeutic index and increased activity. Literally thousands of analogues, obtained by replacement of the ammine-and chloro-ligands by other amines and anionic ligands, respectively, have been systematically screened for activity in experimental tumor models. Some of these analogues have been selected for clinical evaluation, but only very few of them appear to be promising antitumor agents. More recently, cisplatin analogues have been designed and synthesized on the basis of, inter alia, the following considerations: 1) platinum complexes with carrier molecules as ligands should prove useful for achieving increasing drug concentration in tumor tissues; 2) platinum complexes with chemotherapeutic agents as ligands could afford polyfunctional drugs with synergistic action; 3 ) complexes containing more than one platinum atom might be more effective than complexes containing only one platinum atom; 4) platinum complexes could be used as sensitizers in radiation therapy. In this paper, we shall give a brief account of the "traditional" analogues, and then critically discuss what we believe could be the new trends in the design of cisplatin analogues.

The cis influence of a series of anionic ligands X and Y has been evaluated through the magnitude of the Pt-P coupling constants for compounds of formula trans-[PtXY(PPh(3))(2)]. The order of decreasing cis influence was found to be I > Cl > SePh approximately SPh approximately SEt > NO(3) > AcO approximately NO(2) > H > Me > Ph > mtc (mtc = N,N-dimethylmonothiocarbamato-S); moreover, the cis influences of the various ligands was found to be additive. The X-ray structures of three representative compounds (t-: X = Cl, Y = NO(3); t-: X = Cl, Y = AcO and t-: X = Y = NO(2)) have also been determined.