Study On Solvent Effect And Estimation Of Dipole Moments Of An Organic Fluorophore

Abstract The effect of solvents on spectroscopic properties of an organic fluorophore 25-diE-1-4-diphenylaminophenyl methylidine-1-cyclopentanone 25-DPHAPMC belonging to a ketocyanine dye family is analyzed using Lippert-Mataga bulk polarity function Reichardts microscopic solvent polarity parameter and Kamlets multiple linear regression approach. The spectroscopic properties better follows Reichardts microscopic solvent polarity parameter than conventional Lippert-Mataga bulk polarity function. The double linear correlation of Stokes shift with Reichardts microscopic solvent polarity parameter for non-alcohol and alcohol solvents is observed. This indicates that both general solute solvent interactions and specific interactions are contributing to the resultant spectral changes. Kamlets multiple linear regression approach indicates that polarizabilitydipolarity solvent influences are dominating more compared to solvents hydrogen-bond donor and hydrogen-bond acceptor influences. The data on effect of solvents is used to estimate excited state dipole moment using the theoretically determined ground state dipole moment. The excited state dipole moment determined by different methods is compared and analysed. The excited state dipole moment of dye is found to be greater than its corresponding ground state counterpart and ground and excited state dipole moments are almost perpendicular to each other.