Laser-induced emission spectroscopy of acridine cooled in a supersonic jet: the role of dimers and hydrogen-bonding in photophysics of acridine

The formation of acridine (ACD) dimers under supersonic jet-cooling conditi ons has been established by the observations of laser-induced fluorescence and fluorescence excitation spectra. The structure of ACD dimers predicted by using the semiempirical AM1 parametric method suggests the possibility o f the formation of hydrogen bonds between ACD moieties in the dimers. This possibility is verified with use the of the PM3 parametric method. The conf iguration interaction calculations performed for optimized dimer structures gives clear insights into the physical mechanism of the enhancement of the radiative processes in dimers (which, however, seems to be limited to spec ific conditions of supersonic expansions). The well-known role of hydrogen- bonding in the photophysics of ACD in protic liquid solutions is also Suppo rted by the results of preliminary observations under supersonic jet-coolin g. (C) 2000 Elsevier Science B.V. All rights reserved.