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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. March 2006, Volume 5, Number 3, 168-180 |
A Topology-Based Primary Search for Quasi-Linear Conjugated
Organics with Large Ground-To-Excited State Change in Dipole Moment
Marina Dekhtyar and Viktor Rozenbaum
Internet Electron. J. Mol. Des. 2006, 5, 168-180
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Abstract:
A pronounced change in molecular dipole moment on
excitation is the necessary prerequisite for a variety of
significant physicochemical phenomena, such as
solvatochromism, Stark effect, nonlinear optical response,
functioning of biological Brownian motors etc. It is thus
challenging to screen vast arrays of structures so as to find
the promising selections of the molecules remarkable for
their outstandingly large ground-to-excited state changes in
dipole moment. The working model employed is the long-chain
approximation of polymethine compounds which
represents an analytical approximation of the Hückel
molecular orbital method. Computationally, it implies
manipulation of inverse adjacency matrices raised to different
powers. An analytical expression derived in terms of the
topological long-chain approximation has been used to
estimate ground-to-excited state change in dipole moment for
conjugated molecules. The theoretical estimates have been
benchmarked against available experimental data and a
strong correlation, with R = 0.981, has been found between
them. The relationship between the molecular topological
parameters and the change in dipole moment offers the
efficient ways to maximize the latter. Based on the
regularities revealed, a large-scale search among more than
1000 heterocyclic residues have been carried out so as to find
the structures promising sufficiently large differences in
dipole moment between the ground and excited state. As a
result, about 50 residues were selected as candidate structures
for further stages of the relevant molecular design. The LCA
appears to be a convenient tool for estimation of molecular
properties at early stages of molecular design; characteristics
of the candidate structures selected should be refined by an
appropriate higher-level approach.
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