Spectrophotometric and calorimetric studies on the formation of binary (2,2′-bipyridine) nickel(II) and ternary (2,2′-bipyridine) chloronickel(II) complexes in N,N-dimethylformamide

Abstract

Formation of binary (2,2′-bipyridine)nickel(II) and ternary (2,2′-bipyridine) chloronickel(II) complexes has been studied by spectrophotometry and calorimetry in N,N-dimethylformamide (dmf) at 25 °C. Both spectrophotometric and calorimetric data obtained are well explained in terms of the formation of binary [Ni(bipy)]²⁺(bipy = 2,2′-bipyridine), [Ni(bipy)₂]²⁺, and [Ni(bipy)₃]²⁺ and ternary [NiCl(bipy)]⁺, [NiCl(bipy)₂]⁺, [NiCl₂(bipy)], and [NiCl₂(bipy)₂] complexes, and their formation constants, enthalpies, and entropies were determined. Electronic spectra of the individual complexes suggest that all the ternary complexes have an octahedral six-co-ordinate structure, as have the binary complexes in solution.