Effect of Hydroxyl Group on Photo-Physical Properties and Dipole Moments of Fluorescent Dyes: An Experimental and Computational Approach.

In this work, structurally similar, (E)-N'-(2-hydroxybenzylidene)-3,5-di-tert-butyl-2-hydroxybenzohydrazide (A) and (E)-N'-(2-4-dihydroxybenzylidene)-3,5-di-tert-butyl-2-hydroxybenzohydrazide (A-OH) dyes dissolved in general solvents have been studied to explore photo-physical properties, employing solvatochromic shift method, thereby determining their dipole moments in the ground (μ) and excited (μ) states. The molecule A shows a bathochromic shift of fluorescence emission maxima in aprotic solvents whereas a hypsochromic shift in protic solvents. Interestingly, A-OH follows a hypsochromic shift in both protic and aprotic solvents with increasing solvent polarity.

Rotational Diffusion Dynamics of Fluorescein Derivatives in Binary Mixtures of Solvents: An Experimental and Computational Study.

With a view to understand the nature of solute solvent interactions, rotational reorientation times (τ) of three medium sized dipolar laser dyes viz., dichlorofluorescein (DCF), sodium fluorescein (SF) and kiton red (KR) in two binary mixtures namely, aqueous-DMSO and aqueous-1-propanol have been determined employing steady state fluorescence depolarization technique. The experimental results are analyzed in the light of SED hydrodynamic and of Gierer and Wirtz (GW) and Dote, Kivelson and Schwartz (DKS) quasihydrodynamic models.