Computational and Experimental Study on the Dual Fluorescence Phenomenon of 4-(N, N-dimethylamino)- benzonitrile and Related Compounds
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Date
2006-07
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Addis Ababa Universty
Abstract
The behavior of the ground and the first two excited states of
the compound 4-(N,N-dimethylamino)-benzonitrile (4DMABN) have been
studied using both experimental and theoretical methods. For
comparison purpose the ground and the first two excited states of the
compounds 3-(N,N-dimethyl amino)-benzonitrile (3DMABN) and 2,3,6,7-
tetrahydro-1H,5H-pyridol[3,2,1-ij]quinoline-9-carbonitrile (TMABN) have
been studied theoretically. The experimentally achieved absorption
spectrum of 4DMABN has shown two distinct bands. And the emission
spectrum has also two distinct bands, the behavior of which is
dependent on the wavelength of the exciting light. This is attributed to
the presence of two stable conformers of the compound in the ground
state. Excited state calculations using TDDFT method have shown that
the first two excited states of the compound 4DMABN have different
properties in the gaseous and the solvated system. This is in agreement
with the experimental result that the compound shows two emission
bands in the solvent acetonitrile and one band in the gaseous state. The
same theoretical calculation has shown higher excitation energy to the S2
state at the perpendicular conformation of the compound 3DMABN. This
agrees with the absence of a CT band in experiment. For the compound
TMABN the same calculation has shown for the existence of only one
emitting excited electronic state at a considerably twisted conformation.
This is in agreement with the experimentally found single CT band.
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Keywords
Compound 4-(N,N-dimethylamino