Research Article 2- Inorganic Chemistry

Spectroscopic Evidence for the pH Sensitivity and Anion Trapping Capability of
N,N-ethylenebis(acetylacetoneiminato)copper(II) Complex

A.M.K.S.P Adhikari ,M.Y.Udugala-Ganehenege *;
Department of Chemistry, Faculty of Science, University of Peradeniya

Abstract

A shiny crystalline purple colour N,N-ethylenebis(acetylacetoneiminato)copper(II) complex synthesized by template synthesis shows some interesting acid-base properties and capability of binding anions. Single crystal X-ray crystallographic, XRD, UV, IR and CV data were used to characterize the compound. Interestingly, the complex is purple at pH > 7 and colourless in pH <> 7 shows a band at 540 nm. This band disappears and a new band appears around 820 nm giving an isobestic point at 680 nm with the addition of H+ ions into an ethanolic solution of the compound. Interestingly, the band around 540 nm reappears and the solution colour turns to purple again with the addition of OH- ions into the same solution. Stepwise addition of SCN- and Br- to the solution separately at pH < 2 shows an appearance of a new band at 795 nm and 790 nm respectively with the disappearance of the band at 540 nm. This red shift of the d-d band together with the intensity decrease at pH < 2 may be due to the protonation of the ligand environment bonded to the Cu2+ center by decreasing the crystal field stabilization energy (CFSE) of the complex and increasing the symmetry of the system. The blue shift of the d-d band together with the intensity increase with the addition of various anions to the solution at pH < 2 may be due to the CFSE change with the coordination of anions to Cu2+ center and decreasing the symmetry of the system.

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