Syntheses, Characterization and Solvatochromism Study of Heteroleptic Chelated Copper(II) Complexes Containing N,N- dibezyl Substituted Ethylenediamine and Acetylacetonate Ligands

A series of new heteroleptic chelated copper(II) complexes that encompass N,N-dibezyl substituted derivative of ethylenediamine (X-diamine) and acetylacetonate (acac) were prepared. The IR and electronic absorption spectra and the molar conductivity of the complexes are presented and discussed. The molar conductivity values of the complexes in different solvents reveals a predominance of electrostatic interactions between [Cu(X-diamine)(acac)]+ entity and tetraphenylborate anions that counterbalance the positive charge. The resulting complexes with local symmetry of CuO2N2 attain a square-coplanar structure and exhibit the tendency for axial ligation, which is enhanced when an electron-attracting substituent is attached to the phenyl ring of the ethylenediamine chelate. The tendency for axial ligation is particularly fulfilled when suitable nucleophiles (solvents) with different donor abilities exist, leading to solvatochromism. The solute-solvent interactions are revealed by shifts in the ligand field absorption spectra that are enhanced as the donor power of the solvent increases. Linear dependence of the ligand field absorption maximum on solvent donor number is generally observed.