Luminescent Bis(amidinate) Indium Complexes

Bis-amidinate indium(III) monochlorides [(BuN)₂C(Ph)]₂InCl (1), [(BuN)₂C(2-naphthyl)]₂InCl (2), [(BuN)₂C(2-anthryl)]₂InCl (3), [(BuN)₂C(9-anthryl)]₂InCl (4), [(BuN)₂C(9-phenanthryl)]₂InCl (5), and [(BuN)₂C(1-pyrene)]₂InCl (6) were prepared by the reaction of the corresponding Li-amidinate ligand with InCl₃. Single crystal X-ray analysis of compounds 1, 2, 4, and 5 reveals that the In(III) center is bound with two chelating amidinate ligands. The overall coordination geometry around In(III) is distorted trigonal bipyramidal with the chloride occupying one of the equatorial positions. The photophysical properties of these compounds have been analyzed. Compounds 2-6 are emissive in the solution state. The 9-anthryl substituted compound 4 was found to exhibit a maximum quantum yield of 45.5% in dichloromethane. Compound 3 has a maximum lifetime of 11 ns in solution. Theoretical studies were performed to validate the photophysical properties observed in these compounds.