Absorption spectra of some imidazolid-4-one derivatives, the dimerocyanines. IV. Effect of temperature on dye absorption spectrum in the visible region
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Observation at different temperatures of uv absorption spectra of a number of imidazolid-4-one derivatives, dimerocyanines, shows that change in temperature of the solution causes considerable alterations in the absorption curves. In agreement with previous results, this corresponds to a displacement of equilibrium between two dye conformations in solution. One conformation has theβ-dicarbonyl group more coplanar with respect to the plane of the molecule than the other. The transition energy required to convert one form into the other (ΔH) is found from a plot of the logarithms of the equilibrium constants against the reciprocal of the temperature. It is shown that ΔH depends on the substituent at the nitrogen atom in position 3 of the imidazolidone ring.
KeywordsNitrogen Organic Chemistry Absorption Spectrum Nitrogen Atom Equilibrium Constant
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