The effect of H-bonding solvents on the electronically exited states properties of  7-dimethylamino-4-methyl-coumarin and psoralens


L.A. Brueva, N.E. Voropaeva, I.V. Sokolova, J.P. Morozova.    

One of the most important problems of optics and spectroscopy of poly atomic molecules is the determination of how the spectral-luminescent properties are connected with the features of the electronic structure of the molecule. Knowing of such regularities is that allows one to create compounds with the efficient radiating rate. In the case of fluorescent probes or biological labels the sensitive reaction of the fluorophore on the smaller changing of the environment properties is the dominant. The derivatives of coumarin are those satisfying such requirements. A particularity of the structure of the coumarins is the high polarizability of such molecules and their high charge transition rate and high dipole moment values. Representatives of this class take one of the first places among the most efficient green-blue spectral region laser dyes.

    Almost all photochemical and chemical reactions elapse in the liquid medium. Hence, a complete analysis of the mechanism, kinetics and thermodynamics of the reaction should include medium influence consideration, i.e. consideration of the solvatation effects. It is necessary to have a look on the solvent influence into parameters being measured. A location intensity and shape of the absorption and emission bands use to depend on the solvent. This dependence is the result of the molecular interaction forces leading to changing of energy difference between the ground and the first exited states.
    The goal of this investigation is to begin building of the solvation shells of the 7-dimethylamino-4-methyl-coumarin (coumarin 1) molecule and psoralen molecule being relative to the coumarin 1 molecule. Psoralens are widely used in medicine. being combined with the UV-radiation they are successfully used for the cure of skin maladies.