Absorption and fluorescence spectra of 9-anthrol and its chemical species in solution

The absorption, fluorescence, and fluorescence-excitation spectra of 9-anthrol (and/or anthrone) have been observed in various solvents, one of which includes a silicon-aluminium ester (diisobutoxyaluminium triethyl silane[(OBu1 )(2)-Al-O-Si-(OEt)(3) SAE]). The fluorescence spectra of 9-anthrol shows peak wavelengths at 442 nm in benzene, 454 nm in methanol, 539 nm in triethylamine, and 550nm in basic solution, which can be assigned to a neutral, a hydrogen-bonded neutral, an ion pair, and an anionic species of 9-anthrol, respectively. ln ethanol solution including SAE, on the other hand, a new fluorescence peak appears at 473 nm. This new band originates from a complex formed between 9-anthrol and SAE. The excited-state ion pair is formed through the hydrogen-bonded form in water and the complex form in triethylamine. CNDO/S calculations support the experimental results.