A Matrix-Isolation Spectroscopic and Theoretical Investigation of Tris(8-hydroxyquinolinato)aluminum(III) and Tris(4-methyl-8-hydroxyquinolinato)aluminum(III)

Infrared and photoluminescence spectra of matrix-isolated and thin-film samples (both at 11 K) of tris(8-hydroxyquinolinato)aluminum(III) (Alq 3 ) and tris(4-methyl-8-hydroxyquinolinato)aluminum(III) (Almq 3 ) were collected and compared to vibrational spectra generated by B3LYP based density functional calculations. The present infrared spectral results suggest that both Alq 3 and Almq 3 exist primarily in the meridional or C 1 isomeric form with little or no spectral evidence for the presence of the alternate, facial ( C 3 symmetry) geometric isomer. In addition, photoluminescence spectra of these molecules isolated in an argon matrix show vibronic structure in the emission band associated with the S 1 → S 0 transition.