INVESTIGATION OF ANHYDROUS BENZ (F) NINHYDRIN, INDANETRIONE AND 5-METHOXY INDANETRIONE BY ELECTRONIC ABSORPTION AND EMISSION-SPECTROSCOPY AND COMPUTATIONAL CHEMISTRY METHODS

A comparative study of the low lying electronic states and photophysic al aspects of the compounds anhydrous bent (f) ninhydrin (I), indanetr ione (anhydrous ninhydrin) (II) and 5-methoxy indanetrione (anhydrous 5-methoxy ninhydrin) (III) having a cia vicinal cyclic triketo system (three adjacent carbonyl groups in the same plane) has been carried ou t using absorption, emission and excitation spectra in various solvent s at different temperatures. AM 1 and CNDO calculations were carried o ut to find the ground state geometry and to confirm the assignment of various electronic states of I, respectively, An intramolecular charge transfer band in I has been detected and characterised by theoretical calculations. Solvent effect on the (1)(n pi) transitions of these c ompounds has also been studied. The characterisation of charge transfe r complexes of II with various polynuclear aromatic hydrocarbons has b een presented to show that a cis vicinal triketo system attached to an aromatic moiety can function as a potential acceptor. The position of the low lying electronic states of this class of compounds allows the m to exhibit unusual (1)(n pi) fluorescence at room temperature. The compounds also exhibit (n pi) phosphorescence in various solvents at 77 K. (C) 1997 Elsevier Science B.V.