Reduced Fluorescence from Tris-(8-Quinolinolato) Aluminum(III) in the Presence of its Fe(III) Analog

Chloroform (CHCl₃) solutions of tris(8-quinolinolato) Al(III) (AlQ₃), when excited at 395 nm, fluoresce at 520 nm. Addition of tris(8-quinolinolato) Fe(III) (FeQ₃) to these solutions decreases the fluorescence: the ratio of the fluorescent intensity in the presence of FeQ₃, to that in its absence, is exponentially related to [FeQ₃] and independent of [AlQ₃]. We hypothesized that the main cause of this effect was FeQ₃ absorption of the exciting and emitted radiations. The hypothesis was tested in two ways: first, by calculating fluorescence losses using FeQ₃ absorbance measured at 395 and 520 nm; and second, by measuring fluorescence losses when the AlQ₃ was in one optical cell, and the FeQ₃ in others, which were located in either the excitation or emission paths, or both. Comparison between all the results showed that they were not significantly different (P_0.01), thus verifying the hypothesis.