Synthesis and Photophysical Properties of a Series of Dimeric Indium Quinolinates.

A novel class of quinolinol-based dimeric indium complexes (-) was synthesized and characterized using H and C(H) NMR spectroscopy and elemental analysis. Compounds - exhibited typical low-energy absorption bands assignable to quinolinol-centered π-π* charge transfer (CT) transition. The emission spectra of - exhibited slight bathochromic shifts with increasing solvent polarity (-xylene < tetrahydrofuran (THF) < dichloromethane (DCM)). The emission bands also showed a gradual redshift, with an increase in the electron-donating effect of substituents at the C5 position of the quinoline groups. The absolute emission quantum yields (Φ) of compounds (11.2% in THF and 17.2% in film) and (17.8% in THF and 36.2% in film) with methyl substituents at the C5 position of the quinoline moieties were higher than those of the indium complexes with other substituents.