HYDROGEN-BONDING OF AROMATIC-AMINES IN HYDROXYLIC SOLVENTS .2. ABSORPTION AND EMISSION-SPECTROSCOPY OF SUBSTITUTED 7-AMINOCOUMARINS AND 7-AMINOCARBOSTYRILS

The absorption and fluorescence spectra of 7-aminocoumarins and 7-amin ocarbostyrils with different degrees of alkylation were studied in 2-p ropanol (IP), polyfluorinated alcohols and water. The spectral propert ies of substituted 7-aminocoumarins and 7-aminocarbostyrils in hexaflu oro-2-propanol (HFP) are very different from those in 2-propanol due t o the strong hydrogen-bonding (HB) interaction between the solute and the solvent (HFP). The spectral behaviour can be explained in terms of the strength of the HB interaction which depends on the degree of alk ylation of the amino group and the electron affinity of the electron-a ccepting moiety. The absorption spectra indicate that a structural cha nge at the amino nitrogen is induced on formation of strong hydrogen b onds.