Mixed Ligand Binuclear Complexes of Copper(II) and Cadmium(II) with Adenine and 1,4-Diazabicyclo[2.2.2]octane

Abstract

Mixed ligand binuclear complexes of Cu(II) and Cd(II) with adenine (Ade) and 1,4-diazabicyclo[2.2.2]octane (DABCO) have
been synthesized at a metal to ligands (M:L:L′) molar ratio of 1:1:1 in aqueous medium under ambient conditions. All synthesized
complexes are powdery solids of different colours, slightly soluble in hot water and decompose at high temperature. Characterization
of the complexes was accomplished using various analytical techniques, e.g. metal and chloride content analysis, Fourier transform
spectrophotometer (FT-IR), UV-visible spectrophotometer, magnetic measurement, and thermal analyses. The metal and chloride
contents analyses of the complexes reveal to their stoichiometry [M2Cl2(Ade)2(H2O)2(DABCO)]Cl2 [M = Cu(II) or Cd(II)]. Analytical
data suggests that they are homo metal symmetric binuclear complexes comprises of two [MCl(Ade)(H2O)] moieties in between
a DABCO molecule is N,N′-bridge bonded. The arrangements of the ligands around the metal centers are essentially tetrahedral
involving N(9) of deprotonated imidazole moiety, one Cl- ion, one oxygen from the water molecule and one tertiary N atom from
DABCO completing the coordination. Proton migration occurs from N(9) to the N(1) site resulting into a zwitterionic form of
adenine, additionally N(3) site of which is hydrogen bonded with the coordinated water molecule. Electrochemical redox behaviour
of Cu(II) in presence of adenine and DABCO in the aqueous medium was also studied. It exhibits quasi-reversible one-electron
transfer processes.

Dhaka Univ. J. Sci. 70(1): 28-33, 2022 (January)