Complexes of Copper(II) and Adenine at Various pH: Synthesis and Characterization

Abstract

The coordination of Cu(II) ion with purine base is pH dependent and versatile. This study describes the synthesis, structural
components and coordination behavior of Cu(II) with adenine. Three complexes of Cu(II) with adenine have been prepared
at different pH in aqueous solution and ambient conditions. All synthesized complexes are polycrystalline solids of various
colors, air-stable and partially soluble in polar solvents. The complexes were characterized by numerous analytical techniques including compositional analyses, Fourier transform infrared and UV-visible analyses, and thermal investigation. The elemental analyses of the complexes established their chemical composition as [Cu(adeninium)Cl3], [Cu(adenine)(H2O)Cl2] and [Cu(H2O)2(adeninato)2]. Analytical results suggest that the adenine nucleobase could act as a cationic (pH: 5), or a neutral (pH: 7), or an anionic (pH: 8) monodentate ligand in pH facilitated aqueous solution. In the structure, the purine moiety, chloride ion and aqua groups are situated around the copper(II) center is basically in a tetrahedral arrangements. Protonation or deprotonation of the adenine and intramolecular interligand hydrogen bond assisted the pH dependent versatile coordinating behavior of purine base.

Dhaka Univ. J. Sci. 72(2): 84-90, 2024 (July)