Res. Chem. Intermed.
, Vol. 28, No. 7–9, pp. 837–846 (2002)
Also available online - www.vsppub.com
Effect of N-pyridyl substitution and hydrogen bonding
on the deactivation of singlet excited 1,2-naphthalimide
KRISZTINA NAGY and LÁSZLÓ BICZÓK
Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17, 1525 Budapest, Hungary
Abstract—Photophysical properties of 1,2-naphthalimide (1) and N-(4-pyridyl)-1,2-naphthalimide
(2) as well as the effect of their hydrogen bonding with phenols have been studied in toluene. Fluores-
cence emission is the dominant energy dissipation pathway of the singlet excited 1. Introductionof the
4-pyridyl substituent into the imide moiety signi cantly accelerates the internal conversion due to the
ef cient vibronic coupling between close-lying S
excited states, however, the rate of triplet
formation exhibits negligible change. In contrast with the behavior of the corresponding substituted
phenyl derivatives, 2 does not emit dual uorescence because of the less extensive conjugation within
the molecule. Fluorescence quenching with phenols takes place both in dynamic and static processes.
Electron transfer is slower in the hydrogen bonded complex where phenols are linked to the pyridyl
moiety due to the larger distance between the electron donor and acceptor components.
: Fluorescence; internal conversion; hydrogen bonding; electron transfer.
Because of its highly selective and directional nature, hydrogen bonding plays a key
role in fundamental biological processes, construction of self-assembling molecular
architecture and non-covalent synthesis of new materials. It is the most impor-
tant force, which ensures the molecular recognition among the subunits and stabi-
lizes the supramolecular complexes. Hydrogen bonds can mediate photoinduced
electron transfer by the coupling of the electron and proton motions [1, 2]. Re-
cent studies have revealed that the quenching of the excited aromatic ketones with
phenols proceeds via hydrogen bonded complex in which proton transfer contri-
bution to the effective excited state redox potential facilitates the electron transfer
[3, 4]. Hydrogen bonding of quinones  and phenols  signi cantly shifts their
Dedicated to Prof. Henry Linschitz.
To whom correspondence should be addressed.