Polarity and strong sensitivity to external electric field in azacrown oligophenylenevinylene

Abstract

Complex study of quadrupolar azacrown dye (E,E)-5,5́-Bis[2-(4-(4′,7′,10′,13′,16′-pentaoxa-1 azacyclooctadecyl)phenyl)ethenyl]-2,2́-bipyridine 1 was performed. Electronic spectra of absorption and fluorescence in different solvents exhibit strong solvatochromism. Electrooptical absorption measurements (EOAM) were performed to determine the electric dipole moments. These measurements gave large values of dipole moments in the ground μg and Franck–Condon excited state μeFC equal to 6.8 ± 0.14C m and 39.3 ± 0.3C m, respectively. Furthermore, the results of EOAM suggest the existence two conformers in the ground state with close energies of electronic transitions.Density functional theory (DFT) calculations directly show that the shape of this molecule is not planar in the ground state and also allows the existence of two stable conformers with close energies. They appeared due to different orientations of the left and right pyridine fragments of the solute.The energies, electric dipole moments and dependences of dipole moments on the strength of applied electric field were calculated for found stable conformers of 1. DFT calculations with TD / B3LYP / 3-21G and cc-pVDZ (Time Depend) approach show that external electric field increases dramatically the dipole moments of the solute under study. The higher field intensity the larger the excited electric dipole in the range intensities from zero to ∼ 2.8·× 10 9 V/m.