Calorimetric and Spectrophotometric Studies of Ternary Copper(II) Complexes with Bromide Ions and 2,2′-Bipyridyl in N,N-Dimethylformamide

Abstract

Abstract Mixed ligand complexation of copper(II) with bromide ions and 2,2′-bipyridyl (bpy) has been calorimetrically studied in N,N-dimethylformamide (DMF) containing 0.16 mol dm−3 (C2H5)4NClO4 at 25°C. Complexation of the metal ion with 2,2′-bipyridyl has been also studied in the same solution. The calorimetric titration curves obtained were satisfactorily explained in terms of formation of the mononuclear [CuBrp(bpy)q](2−p)+ (denoted as (1pq)) complexes such as (101), (102), (103), (111), (121), and (112), and their formation constants and enthalpies were determined. The mixed ligand (111), (112), and (121) complexes are quite stable and yielded to a large extent in the DMF solution. Electronic spectra of these complexes have been measured in DMF over the range 400–1500 nm. The thermodynamic quantities of formation and electronic spectra of the complexes thus obtained are discussed in connection with the coordination structure of the complexes in DMF. The formation of the five-coordinate [Cu(bpy)2(dmf)]2+ and [CuBr(bpy)2]+ complexes is suggested in the DMF solution as well as in crystal.