Excited-state dipole moments solvent-shift methods

Prabhumirashi and Kunte [181] have proposed a new procedure employing Bakhshiev s equation for solvatochromic frequency shifts for excited-state dipole moments and specific solute -solvent interaction energies based on absorption spectra only, without using emission spectra. Suppan [182] has expanded upon the solvatochromic shift method and discussed the effect of the medium on the energies of electronic states and Ghoneim and Suppan [183] discussed solvatochromic shifts of non-dipolar molecules in polar solvents. 

Ayachit and Tonannavar [184] have critically examined Suppan s method and developed two improvements intended to resolve the uncertainty concerning the direction of excited-state dipole moments. Kurbako et al. [18S] have developed a new solvent shift approach based on a theory of universal intermolecular interactions. Abe has proposed a method of estimating the angle between ground- and excited-state dipole moments based on improved solvatochromic... 

The method is based on the ability of the excited state of suitable chromophores to both drive and respond to motions in their immediate environment. For example, coumarin excited states have a large dipole moment that causes nearby charged groups to move to stabilize the dipole. As these groups move and reduce the energy of the excited state, the fluorescence shifts toward the red. In simple solutions, this time-resolved Stokes shift (TRSS) experiment measures the time-dependent polarity of the solvent surrounding the coumarin [9]. 

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