Crystal structure, solvatochromism and estimation of ground and excited state dipole moments of an allyl arm containing Schiff base: Experimental and theoretical calculations

Abstract

An allyl arm containing Schiff base (L) was prepared by the condensation of 1-[4-(allyloxy)-2-hydroxyphenyl]ethanone with 1,3-diaminopropane. The L was characterized on the basis of the results of elemental analysis, spectral techniques and single crystal X-ray crystallography. The electronic absorption and fluorescence spectra of L were recorded in solvents of different polarities at room temperature, and the data were used to study the solvatochromic properties. The hydrogen bonding and tautomeric equilibria in both of solution and the solid state are explained. The ground state (μg) and excited state (μe) dipole moments were determined by using Lippert–Mataga, Riechardt, Bakhshiev and Kawski–Chamma–Viallet solvatochromic shift methods based on the solvent polarity parameters. Solute–solvent interactions were studied by linear solvation energy relationships using dielectric constant, refractive index and Kamlet–Taft parameters (α=H-bond donor ability; β=H-bond acceptor ability). The dipole moment values of L were calculated in the gas phase with TD-DFT/B3LYP. The HOMO and LUMO energy levels, molecular electrostatic potential energy surface, natural bond orbital analysis and Mullikan charges demonstrate the existence of intramolecular charge transfer within the molecule.