A. Demeter et al., SPECTROSCOPIC PROPERTIES OF AROMATIC DICARBOXIMIDES .2. SUBSTITUENT EFFECT ON THE PHOTOPHYSICAL PROPERTIES OF N-PHENYL-1,2-NAPHTHALIMIDE, Journal of the Chemical Society. Faraday transactions, 90(18), 1994, pp. 2635-2641
Citations number
21
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
Absorption and fluorescence spectra, fluorescence decay times, fluores
cence quantum yields and triplet yields have been determined for N-phe
nyl-1,2-naphthalimide and its phenyl-substituted methyl derivatives in
different solvents. N-Phenyl-1,2-naphthalimide emits long-wavelength
fluorescence in hexane (lambda(f)(max) = 550 nm) which is red shifted
by methyl substitution at the meta and para positions of the phenyl ri
ng and by using a solvent of higher polarity. The fluorescence decays
on the sub-nanosecond timescale. When the N-phenyl-1,2-naphthalimide h
as o-methyl substituents in the phenyl group, they emit dual fluoresce
nce. The location of the short-wavelength component is constant while
that of the long-wavelength component is blue shifted as a result of o
-methyl substitution. Ortho substitution also increases the decay time
of the long-wavelength fluorescence. The results are explained in ter
ms of vibronic interaction between the S-1(pi pi) and S-2(n pi*) exci
ted states (pseudo-Jahn-Teller effect) which is enhanced by solvent re
laxation and twisting of the phenyl ring towards a coplanar geometry.