DEACTIVATION PROCESSES AND HYDROGEN-BONDING OF EXCITED N-SUBSTITUTED ACRIDONES

The photophysical properties of 10-decyl- and 10-propenyl-9-acridones, important emitters in electro- and chemiluminescence, are investigate d in dependence of the solvent polarity and its hydrogen bonding abili ty at room temperature as well as in frozen matrix at 77 K. Fluorescen ce is inefficient in non-polar solvents at room temperature due to fas t intersystem crossing but increases with solvent polarity due to the inversion of the S-1(pi pi) and the T(n pi*) states. In the case of 9 -[10-(1 -propenyl)]-acridone the dependencies of the fluorescence spec trum and quantum yield on the FT(30) solvent parameters indicate that intermolecular hydrogen bonded solute-solvent complexes are formed in the excited state, inducing efficient non-radiative deactivation. (C) 1998 Elsevier Science B.V.