TERNARY PALLADIUM(II) COMPLEXES: SYNTHESIS, CHARACTERIZATION AND DNA BINDING STUDIES

Abstract

In the present work three novel heteroleptic Palladium(II) dithiocarbamate complexes; Chlorido {( dibenzylamine-1- K2 S,S ')(tris( 4-chlorophenyl)phosphine )palladium(II)} (1), Chlorido {( dibenzylamine-1- K2 S,S ')(tris( 4- fluorophenyl)phosphine )palladium(II)} (2), Chlorido {( dibenzylamine-1- K2 S,S')(tris( 4-trifluoromethylphenyl)phosphine)palladium(II)} (3) have been successfully synthesized by reacting palladium(II) chloride with sodium salt of N benzyl-1-phenylmethanarnine and substituted triphenylphosphine ligand usmg methanol and acetone as solvents and characterized using FTIR and NMR spectroscopy. The IR frequencies reported for dibenzylamine dithiocarbamate ligand are D(C-S) 993 cm,l, D(C=S) 1076 cm,l and D(N-CSS) 1495 cm'1.74 D(C-S), D(C=S) and D(N-CSS) were shifted to 824.86 cm,l, 1094.02 cm,l, 1493.75 cm'l(complex 1), 829.93 cm,l, 1059.66 cm,l and 1514 cm,l (complex 2) and 813.72 cm,l 1082.11 cm,l and 1478.46 cm,l (complex 3) respectively, which conftrms the binding of ligand to the metal centre. In case of IH-NMR, the peaks appear due to the protons of aromatic ring and -CH2 group which are spectator in both cases and thus have no significance in the confirmation of complexation. In NMR spectroscopy, the shift in the peak of -CS2 fi'01TI 182.8 ppm (ligand) to 208.6 ppm, 208.5 ppm and 208.1 ppm in complex 1, 2 and 3 respectively exhibited the complexation of ligand to the metal center. More than one peaks slightly above 129 ppm are additional for triphenylphosphine ligands, only present in the NMR of three complexes and are absent in case of N -benzyl-l phenylmethanamine. The interaction of all three complexes with CT-DNA was investigated using absorption spectroscopy, which have confirmed covalent (intrastrand) as well as electrostatic modes of interaction. Thermodynamic (6 0 , 6H, 6S) and kinetic (Kb, 6 Amax) parameters were also calculated. Complex 1-3 have concave Scatchard Plots, sigmoidal Kolt's plots and value of Hill's coefficient greater than unity showing positive cooperative behaviour. Cooperativity of the complexes is the representation of their ability to promote binding of further complex molecules after the binding of pioneer molecule to DNA. High negative magnitude of 60 and positive values of 6 S are depicting the spontaneity of drug-DNA interaction and entropy driven nature of reactions respectively. DNA binding and denaturing studies revealed the following sequence: 1 > 3 > 2.