T. Soujanya et al., ROLE OF NONFLUORESCENT TWISTED INTRAMOLECULAR CHARGE-TRANSFER STATE ON THE PHOTOPHYSICAL BEHAVIOR OF AMINOPHTHALIMIDE DYES, Journal of physical chemistry, 100(9), 1996, pp. 3507-3512
Photophysical behavior of 4-aminophthalimide and its N,N-dimethyl deri
vative is studied in a series of solvents. A comparison of the fluores
cence properties of the two compounds reveals that they behave quite d
ifferently despite their structural similarity. The efficient nonradia
tive decay of the dimethyl derivative in polar media is interpreted in
terms of a nonemitting twisted state. Semiempirical calculations base
d on the AM1 method have been performed, and the results support the t
wisting mechanism. Calculations of the ground and excited state profil
es as a function of torsion angle provide a clear picture of whether t
he twisting can influence the photophysical behavior of this class of
dyes. The results provide insight into the design of efficient dye sys
tems.