A Series of Quinolinol-Based Indium Luminophores: A Rational Design Approach for Manipulating Photophysical Properties

An approach to the design of a series of quinolinol-based indium complexes that can exhibit different optical properties is proposed. Mono-incorporated (Inq₁ and InMeq₁), bis-incorporated (InMeq₂), and tris-incorporated (Inq₃ and InMeq₃) indium quinolinate complexes have been prepared. These complexes have also been characterized by X-ray crystallography. The photophysical properties of these complexes have also been examined by a combination of experimental and theoretical techniques. The indium complexes with a single quinolinol ligand (Inq₁ and InMeq₁) showed higher quantum efficiency than those with two or three quinolinate ligands; in particular, InMeq₁ exhibited the highest quantum yield [φ_PL = 59% in poly(methyl methacrylate) film]. The insights into the nature of these findings were obtained by the sequential synthesis of the quinolinol-based indium luminophores and a detailed investigation of their structural stability.