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Dipole moments of 4'-aminoflavonols determined using electro-optical absorption measurements or molecular Stark-effect spectroscopy

Dipole moments of 4'-aminoflavonols determined using electro-optical absorption measurements or molecular Stark-effect spectroscopy. Nemkovich, N. A.; Baumann, W.; Pivovarenko, V. G. (B. 101442-35-7 and 153499-29-7 are also occured in this study.I.Chemical with cas number 6889-78-7 also plays role. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk 220072, Belarus). Journal of Photochemistry and Photobiology, A: Chemistry, 153(1-3), 19-24 (English) 2002 Elsevier Science B.V. CODEN: JPPCEJ. ISSN: 1010-6030. DOCUMENT TYPE: Journal CA Section: 74 (Radiation Chemistry, Photochemistry, and Photographic and Other Reprographic Processes) Section cross-reference(s): 73, 76 The electro-optical absorption measurements (EOAM) were used to measure the dipole moments of the normal form of 4'-(methoxy)-3-hydroxyflavone (FOM), 4'-(dimethylamino)-3-hydroxyflavone (FME), and 4'-N-(15-azacrown-5)-3-hydroxyflavone (FCR). For these probes the excited state intramol. proton transfer (ESIPT) takes place. For comparison, the dipole moments of 4'-(dimethylamino)-3-methoxyflavone (FME3ME), for which ESIPT is lacking, were measured. In the case of FCR, FME, and FME3ME the equilibrated ground (mg) and excited Franck-Condon state (meFC) elec. dipole moments are parallel to each other and also parallel to the transition dipole moment. The elec. dipole moments of FCR, FME, and FME3ME in their ground state have values within the range (14.1-17.7)′10-30 C m. Upon optical excitation, the dipole moments increase by (47.1-50.4)′10-30 C m. Among the studied flavonols, mg and meFC decrease in the order FME3ME>FCR>FME. This effect can be explained by the existence of an intramol. H-bond for FCR and FME, which partly compensates a neg. charge on the carbonyl oxygen in the ground state and thus diminishes the electron-donating ability of the amino-group in the excited Franck-Condon state. For FOM the equilibrated ground and excited Franck-Condon state dipole moments of the normal form have values of 9.4′10-30 C m and 26.3′10-30 C m, resp. The smaller values of the dipole moments for FOM, in comparison with other flavonols, is caused by the absence in FOM of a strong electron-donating group, such as the amino-group. The dipole moments are not parallel and the angles between the different dipole moments are in the range 4-55°. ..