TY - JOUR
T1 - Bimanes. 22. Flexible fluorescent molecules. Solvent effects on the photophysical properties of syn-bimanes (1,5-diazabicyclo[3.3.0]octa-3,6-diene-2,8-diones)
AU - Kosower, Edward M.
AU - Giniger, Rina
AU - Radkowsky, Annette
AU - Hebel, David
AU - Shusterman, Alan
PY - 1986
Y1 - 1986
N2 - The photophysical properties of bimanes (1,5-diazabicyclo[3.3.0]octa-3,6-diene-2,8-diones) exhibit two types of behavior in solution. The maximal absorption energies, the maximal emission energies, the quantum yields of fluorescence, and the radiative rate constants all decrease (a) moderately fast with solvent polarities up to the intermediate range and (b) slowly from the intermediate polarity range up to water. The bimanes examined include syn-(hydro,hydro)bimane (1), syn-(methyl, fluoro)bimane (2), syn-(methyl,hydro)bimane (3), μ(0)-syn-(methylene,methyl)bimane (4), syn-(methyl,chloro)bimane (5), and syn-(methyl,methyl)bimane (6). The effects are interpreted in terms of two conformational isomers, "bent" and "quasi-planar", for both the ground and excited states. The magnitude of the solvent sensitivities of the photophysical properties, the nature of the conjugation, and the shapes observed in crystal structures suggest that solvent polarity affects the conformation of the bent conformers. The equilibrium between bent and quasi-planar forms may not vary much with solvent polarity, but the appearance of the emission spectrum changes drastically due to substantial differences in the radiative rates for the two conformers.
AB - The photophysical properties of bimanes (1,5-diazabicyclo[3.3.0]octa-3,6-diene-2,8-diones) exhibit two types of behavior in solution. The maximal absorption energies, the maximal emission energies, the quantum yields of fluorescence, and the radiative rate constants all decrease (a) moderately fast with solvent polarities up to the intermediate range and (b) slowly from the intermediate polarity range up to water. The bimanes examined include syn-(hydro,hydro)bimane (1), syn-(methyl, fluoro)bimane (2), syn-(methyl,hydro)bimane (3), μ(0)-syn-(methylene,methyl)bimane (4), syn-(methyl,chloro)bimane (5), and syn-(methyl,methyl)bimane (6). The effects are interpreted in terms of two conformational isomers, "bent" and "quasi-planar", for both the ground and excited states. The magnitude of the solvent sensitivities of the photophysical properties, the nature of the conjugation, and the shapes observed in crystal structures suggest that solvent polarity affects the conformation of the bent conformers. The equilibrium between bent and quasi-planar forms may not vary much with solvent polarity, but the appearance of the emission spectrum changes drastically due to substantial differences in the radiative rates for the two conformers.
UR - http://www.scopus.com/inward/record.url?scp=0008527363&partnerID=8YFLogxK
U2 - 10.1021/j100280a014
DO - 10.1021/j100280a014
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AN - SCOPUS:0008527363
SN - 0022-3654
VL - 90
SP - 5552
EP - 5557
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
IS - 22
ER -