DFT and ab initio study on non-linear optical (NLO) properties of some organic complexes with different conjugate linker and substituent groups

• Published in: Optics and spectroscopy Vol. 113; no. 3; pp. 240 - 258
• Main Authors: Tang, Guodong, Zhao, Jianying, Jiang, Zhengjing, Kou, Shanshan, Ju, Xuehai, Wei, Changmei
• Format: Journal Article
• Language: English
• Published: Dordrecht SP MAIK Nauka/Interperiodica 01.09.2012
• Subjects: Lasers; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy; Spectroscopy of Atoms and Molecules; Schiff Base; LUMO Orbital; Homo Orbital; Time Dependent Density Functional Theory; Schiff Base Compound
• ISSN: 0030-400X; 1562-6911
• DOI: 10.1134/S0030400X12090068

A series of Schiff-bases chromophores containing imine or double C=C bond linkers between the donor and acceptor have been studied by first-principles calculations. The molecular structures, electronic properties and second order nonlinearities were investigated by DFT and ab initio methods. The optimized structural parameters of these Schiff-base derivates showed that these compounds are stable. The results of TD-DFT calculations indicate that the derivatives with the heterocyclic and imine linker have a red shift absorption compared to derivatives with the double C=C or N=N bonds. The analysis of the frontier molecular orbitals indicates that the CN group and the heterocycle linked by the CN or imine group has contribution to the LUMO orbital while the groups N(CH 3 ) 2 and the benzene ring linked by the double C=C or N=N bond have contribution to the HOMO orbital. The CN and the heterocyclic acceptors enable the derivatives to have a larger first static hyperpolarizability. However, the compounds 3-{4-[(4-Dimethylamino-phenylimino)-methyl]-pyridin-1-yl}-propanel-1-sulfonoperoxoic acid and 3-{4-[(4-Dimethylamino-phenylimino)-methyl]-quinolin-1-yl}propanel-1-sulfonoperoxoic acid with a substituent also have large first static hyperpolarizabilities due to the overwhelming contributions of electron density of the group to the HOMO orbital, that is, the HOMO orbital were constituted by the SO 3 − group only. In order to understand the influence of the energy gap (Δ E ) between the HOMO and the LUMO orbitals on the first static hyperpolarizability, we calculated the energy gap (Δ E ) of all Schiff-base compounds. The results show that the smaller the HOMO-LUMO energy gap the larger the first static hyperpolarizability. The present study demonstrated that these compounds which have pure C=N double bond and heterocyclic substitution groups may have potential applications in the development of NLO materials.