Synthesis, characterization and antitumor activity of platinum(II) and palladium(II) complexes with ethyl-8-ylmethylphosphonate

There has been a continued interest in the chemistry and biochemistry of phosphonic and aminophosphonic acid derivatives because of their wide range of biological and pharmacological properties, with possible application from medicine to agriculture. Another interesting aspect regarding this kind of compounds arises from their ability of forming metal complexes, which might be also of interest in living systems. In this field our systematic study is directed to platinum(II) and palladium(II) complexes of quinoline and aniline-based alkyl phosphonates, which might be of interest as potent antitumor agents [1, 2]. In this report we describe the synthesis, spectroscopic analysis and biological properties of platinum(II) and palladium(II) complexes of monoethyl quinolyl-8-ylmethylphosphonate. This organophosphorus ligand depending on reaction conditions forms neutral and ionic metal complexes. In the basic media acts as a bidentate ligand through the quinoline nitrogen and the deprotonated phosphonic acid group, while under acidic conditions are formed the quinolinium tetrahaloplatinum, tetrahalopalladium, trihalopalladium and hexahalodipalladium salt complexes, respectively. All complexes were evaluated for their in vitro cytostatic activity in an epidermoid human carcinoma (KB) and murine leukaemia (L1210) cell lines. The results obtained are compared with those obtained for the platinum(II) and palladium(II) complexes of the corresponding dialkyl esters of quinolyl-8-ylmethylphosphonate and discussed with respect to their structure-activity relationship.