β-diketonate, β-ketoiminate, and β-diiminate complexes of difluoroboron

A series of beta-diketonate, keto(aryl)iminato, and beta-bis(aryl)iminato complexes of difluoroboron, twenty in total, have been prepared to assess the impact of chelate ring and aniline substitution on the structural, electrochemical, and photophysical properties of these ubiquitous chelates. DFT (B3LYP/6-31G*) calculations supplemented the experimental results and both demonstrated that replacing oxygen with the more electron-donating aniline groups serves to only fine-tune the electronic properties because both the HOMO and LUMO energies are affected by such substitution. The electronic properties of all compounds are most greatly influenced by the nature of the substituents bound to the carbon portion of the chelate ring. Each difluoroboron complex undergoes two ligand-based, one-electron reductions where the first reduction potential becomes less favorable with increasing aniline substitution. Similarly, replacing oxygen with the more electron-donating aniline groups gives rise to slightly red-shifted absorption and emission processes. Substitution on the aniline ring has little, if any, influence on the electronic properties of the resultant complexes. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).