The absorption and fluorescence study of 1,4,5,8-naphthalenetetracarboxy diimides in their low-energy 1 and 1 electronic states. The Franck–Condon analysis in terms of CASSCF method

The electronic structure of the low-energy states of 1,4,5,8-naphthalenetetracarboxy diimide ( 1 ) is investigated in terms of CASSCF method. At this level of approximation the Franck–Condon (FC) parameters were evaluated for the 13 totally symmetric modes of ( 1 ) molecule in its dipole-allowed low-energy 1 1 B 2 u and 1 1 B 3 u electronic states. These parameters are then employed to simulate the vibrational structures of absorption and fluorescence spectra of N , N ′ -dibutyl ( 2 ) and N , N ′ -bis-hydroxypropyl ( 3 ) derivatives of naphthyl diimides measured in the region corresponding to the low-energy 1 1 A g → 1 1 B 2 u and 1 1 A g → 1 1 B 3 u overlapping transitions.