Luminescence Properties of Some (Z-E)-4,4'-bis(2-benzoxazolyl)stilbene Derivatives: Theoretical Study

Abstract

The influence of electron-withdrawing (nitro, cyano) and electron-donating (methyl, chloro) groups on these compounds was investigated. The charge transferred between atoms in natural bond orbitals was found to be higher than the Mulliken charge in (E)-4,4'-bis(3-nitro-2-benzoxazolyl)stilbene )BBS) 2-1. The HOMO-LUMO energy gap in the ground state of (Z)-4,4'-bis(3-nitro-2-benzoxazolyl)stilbene, 1-1, is 3.34 eV. In the excited state, the energy gap decreases to 2.93 eV. The difference between the two energy gaps is 0.41 eV. In 2-1 the difference between two energy gaps of the ground and excited states decreases to 0.32 eV, indicating intramolecular charge transfer. The absorption wavelength of this compound is 411.2 nm in the gas phase and 468.4 nm in solution due to the bathochromic effect and interaction between the isomer and the solvent, which falls within the blue light wavelength range of 420-470 nm. The H-index value of 2-1 has higher absorption intensity. Isomer 2-1 is a more suitable option for use in optical brighteners in the textile industry.