Quantitative studies of DNA binding with trans complexes of PtII and PdII featuring tetrazolylacetic acids and their derivatives as ligands

The interaction of calf thymus DNA (CT DNA) with trans-[PtCl2L2] and trans-[PdCl2L2] complexes (L-5-methyl-1H-tetrazol-1-ylacetic acid and its ethyl, butyl, and isobutyl esters; ethyl esters of 2-R-2H-tetrazol-5-ylacetic acids, R = Bu-t, CH2CH2OH) have been quantitatively studied by a spectrophotometric method. The binding constants (K-b) of the tetrazolecontaining coordination compounds with CT DNA at pH 7.2 and 298 K are in the range of (3.67-5.93)center dot 10(5) mol L-1 for the Pd-II complexes and (7.82-13.30).10(5) mol L-1 for and the Pt-II complexes, respectively. The K-b values, as well as negative values of Delta G(b) (-(31.7-34.9) kJ mol(-1)) indicate the effective binding between the studied complexes and CT DNA.