ISSN:
0192-8651
Keywords:
asymmetrization effects
;
electron donor-acceptor
;
materials for nonlinear optics
;
population analysis
;
dipole alignment
;
structural effects of conjugation
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Computer Science
Notes:
Asymmetric donor-acceptor-substituted π-conjugated systems with low dipole moments and structural components that favor parallel alignment of neighboring molecules are potential molecular organic materials with nonlinear optical properties for which near prefect dipole parallel alignment is possible. The asymmetrical 4-methoxysubstituted acetophenone azines with the substituents fluorine (1), chlorine (2), bromine (3), cyano (4), and nitro (5) in the 4′-position have been studied in this context, and for 2 and 3 the dipole parallel alignment has indeed been accomplished in crystals of the pure material. In the present study, the effects of asymmetrization on the structure and the electronic structures of the ground states of 1-5 have been explored at the RHF/6-31G* level. The properties of the optimized structures of the azines 1-5, a comparative analysis of asymmetrical and symmetrical azines, and natural population analyses, all show no significant evidence for conjugation over the azine bridge. The concept of azine spacers as “conjugation stoppers” is useful and the dipole moments of asymmetrical azines are relatively small. The analysis suggests that the charge transfer between the donor and acceptor contributes to the dipole moment much less than is generally assumed. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1130-1140, 1998
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
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