Synthesis and spectral studies on platinum complexes with mono- and bidentate N-donor organic ligands

Abstract

Platinum(II) complexes of types PtLX 2, PtL 2X 2, PtLX″ and the Pt(IV) complexes PtLXY (where L = mono- or bidentate organic ligand containing nitrogen donor atoms; X = Cl or Br; X′ = oxalate or malonate and Y = Br) have been synthesized and characterized from their elemental analysis, IR and X-ray photoelectron spectral data. The Pt 4f 7/2 binding energies indicate that 1,8-naphthalene-diamine ligand is a better donor of electron density to the metal than other ligands studied here. The Cl 2p 3/2 binding energies in the square planar Pt(II) complexes are observed in the range 198.8 ± 0.8 eV. The ν (PtCl) vibrations ( ca 335 and 320 cm −1) corresponding to two cis-Cl ligands were observed in the IR spectra. The extent of the interaction between cis-dichloro- bis-(theophylline)platinum(II) with calf thymus DNA has beenstudied. The UV difference spectra resulting from aquated Pt II(theoph) 2-DNA interaction exhibit bands at 282 and 292 nm attributable to the change in the electron distribution of the base moieties induced by binding with platinum and due to the loss of base stacking. Melting profiles for the DNA samples treated with Pt-complex showed decrease in the melting temperature. Binding of the guanine residues of the DNA, involving probably (N7)-0(6) positions to the metal is implied.