Effect of tetraethylene glycol side chain conformation on chiroptical properties of chirality‐induced benzocoumarin

Abstract

Coumarins are multifaceted molecules with compelling fluorescence features. Along with biocompatible properties, they have recently been used in chiroptical studies. The chirality induction to benzo[f]coumarin moiety at the third position was investigated in this study. The chromophore derivatized with homochiral alanine and phenylalanine resulted in identical spectroscopic properties. When the chiroptical properties are concerned, the distinct CD spectra of both structures are also changed significantly by altering the organic solvent. Inter-and intra-molecular hydrogen bonding affects the CD spectra along with the chiroptical signal. The phenylalanine-benzo[f]coumarin structures were modified with TEG units to increase water solubility and enhance ordered aggregations. The chiroptical properties of the compounds were analyzed in organic solvents with spectroscopic techniques. It was found that coumarin is not only sensitive to the chiral unit attached but also that any conformational change on the side chain affects the chiroptical signal. Timedependent DFT calculations in the gas phase supported these results.