The Optical Properties, UV-Vis. Absorption and Fluorescence Spectra of 4-Pentylphenyl 4-n-benzoate Derivatives in Different Solvents.

In this paper, electronic absorbance and fluorescence spectra of 4-Pentylphenyl 4-n-benzoate derivatives have been measured in 29 solvents, which are non-polar, polar protic and polar aprotic solvents, and electronic transitions that vary depending on the solvent are identified. As the solvent polarity increases, the forbidden energy difference between the frontier orbitals decreases. The statistical models in order to describe the solvent effect were derived using different solvent parameters. Quite complex and multiple absorbance transitions were observed in different solvent environments. Local fluorescence transition and intramolecular charge transfer occurred in the fluorescence spectra. Absorbance transitions are global transitions, and π*←π is the absorbance electronic transition. The frontier molecular orbitals and electrostatic potential surface were founded using quantum chemical calculations. Refractive indices were found with five different methods and forbidden energy gaps were found with the Tauc method. The forbidden energy ranges were found around 4.1 and 4.5, and the forbidden energy gap decreased as the alkyl chain became longer. All compounds can be defined as insulation materials according to the forbidden energy range. Refractive index values close to the E7 liquid crystal mixture used in liquid crystal display panels were found in the investigated liquid crystals.