Synthesis, Crystal Structure, and Chromotropic Properties of Mixed-Ligand Nickel(II) Complexes with 1,3-Diketonate and P–N Bidentate Ligands

Abstract

Abstract Mixed-ligand nickel(II) complexes Ni(acac)(dmap)X, [Ni(acac)(dmap)]BPh4 (1), [Ni(acac)(dmap)]BF4 (2), and [Ni(acac)(dmap)NO3] (3) (where acac = acetylacetonate and dmap = 1-dimethylamino-2-diphenylphosphinoethane) have been obtained for the first time and their X-ray single-crystal structures have also been determined. This series of complexes show different structures, hence colors, in the solid state depending on the coordination strength of the anion X−: the complexes with tetraphenylborate and tetrafluoroborate having no coordination ability are square-planar and orange, while on the contrary, the coordinating nitrate ligand produces an octahedral and pale blue complex. In solution, two types of solvatochromism due to solute–solvent interaction and solute–solute–solvent interaction have been observed and these spectral behaviors are attributed to the changes in their geometries due to the donor/acceptor properties of the solvents. The thermochromic behavior of complex 1 has also been studied with temperature variation UV–vis spectra in various solvents. The behavior of these solvato- and thermo-chromisms of these complexes is due to the intermediate ligand field strength created by the dmap and the acac ligands.