The interaction of organoselenium trans-palladium(II) complexes toward small-biomolecules and CT-DNA

Abstract

A series of organoselenium trans-palladium(II) complexes 1 (bis(2-(phenylselanylmethyl)oxolane)dichloropalladium(II)), 2 (bis(2-(phenylselanylmethyl)oxane)dichloropalladium(II)) and 3 (bis(2,2-dimethyl-3-(phenylselanyl)oxane)dichloropalladium(II)) have been used to investigate reactivity of this specific type of complexes toward different bio-molecules. This system is of special interest because only little is known about the substitution behavior of organoselenium palladium(II) complexes with trans configuration. The substitution of coordinated chloride by a series of small bio-molecules (l-Met, l-His, l-Cys, GSH and 5′-GMP) was studied under pseudo first-order conditions as a function of nucleophile concentration and temperature using stopped-flow technique. The results for the studied complexes indicate that the complex 1 reacts faster compared to the complexes 2 and 3, which is caused by steric effects. The sulfur-donor bio-molecules have shown better reactivity than nitrogen-donor bio-molecules. The activation parameters indicate that substitution occurs by an associative mechanism which is supported by the significantly negative activation entropies. Furthermore, the interaction of these organoselenium trans-palladium(II) complexes with calf thymus DNA (CT-DNA) was further examined by absorption (UV–Vis) and emission spectral studies (Ethidium bromide displacement studies). Overall, the studied complex exhibited good DNA interaction ability.