Synthesis, characterization, DNA binding, and cytotoxic studies of dinuclear complexes of palladium(II) and platinum(II) with 2,2-bipyridine and α,ω-diaminoalkane-N,N′-diacetic acid

Abstract

The synthesis of four α,ω-diaminoalkane-N,N′-diacetic acid and their dinuclear 2,2′-bipyridine palladium(II) and platinum(II) complexes of general formula [M 2(bipy) 2(DADA)] (NO 3) 2 (where M is Pd(II) or Pt(II), bipy is 2,2′-bipyridine, DADA is dianion of 1,4-diaminobutane-N,N′-diacetic acid (DBDA), 1,6-diaminohexane-N,N′-diacetic acid (DHDA), 1,8-diaminooctane-N,N′-diacetic acid (DODA), or 1,10-diaminodecane-N-N′-diacetic acid (DDDA) has been achieved. They have been characterized by elemental analysis, conductivity measurements, electronic absorption, and infrared and variable temperature 1H NMR spectroscopy. The above eight dinuclear palladium(II) and platinum(II) complexes have been tested for cytotoxicity against P388 lymphocytic leukemia cells. Out of them, [Pt 2(bipy) 2(DDDA)(NO 3) 2 and [Pd 2(bipy) 2(DBDA)](NO 3) 2 show lower I.D. 50 values as compared to cisplatin. The binding of [Pt 2(bipy) 2(DODA)](NO 3) 2 and [M 2(bipy) 2(DHDA)](NO 3) 2 with calf thymus DNA (deoxyribonucleic acid) has also been studied. [Pt 2(bipy) 2(DODA/DHDA)](NO 3)2 complexes show high positive cooperative binding to DNA, with Hill coefficients of 1.6 to 1.9, respectively, whereas [Pd 2(bipy) 2(DHDA)](NO 3) gives a biphasic Scatchard plot with two different binding sites or with negative cooperativity.