Solvatochromism of Quinoline-390 and Rhodamine-800: Multiple Linear Regression and Computational Approaches

Abstract

The electronic absorption and emission spectra of laser dyes quinoline-390 and rhodamine-800 in distinct organic solvents have been analyzed to understand conventional interactions of solvents on the intensities, peak positions of both absorption and emission spectrum. The relationship between absorption spectrum (λmax) and solvatochromic constants (ε, n, E) indicates that the peak positions are fundamentally influenced by non-specific and specific kind of interactions between the solute and solvent. Solvent effects on the electronic absorption band shift are characteristics of the degree of charge rearrangement of the solute molecules upon electronic excitation. These spectral shifts reflect the effect of the equilibrium solvents association across the energized solute particle, which adjusts inertially as a result of quick charge realignment upon radiative deactivation to the lowest electronic state. Spectral regression study techniques were carried out for the qualitative chemical analyses of these compounds, which provides an opportunity to assess electrical-optical molecular constants within the excited electronic conditions. Further TD-DFT computational techniques for optimized geometry, electronic structure and Mulliken charge distribution in vacuum and ethanol solvent were carried out to acquire additional knowledge of the molecular arrangement and electronic properties of these laser dyes.