Synthesis, characterization and theoretical calculations of four chiral schiff base materials for second harmonic generation applications

Abstract

In this work, chirality combining schiff base molecular character was used to design noncentrosymmetric materials with hyperpolarizability for second harmonic generation applications. Four chiral schiff base molecualers, two pairs of enantiomers, (1S,2S)(-)-diphenen(3,5-salicylaldehyde) (S,S-DS), (1R,2R)(+)-diphenen(3,5- salicylaldehyde) (R,R-DS), (1S,2S)(-)-diphenen(9-anthraceneca) (S,S-DA) and (1R,2R)(+)- diphenen(9- anthraceneca) (R,R-DA) have been successfully designed and synthesized. And four crystal materials, S,S-DS·acetonitrile (compound 1), R,R-DS (compound 2), S,S-DA (compound 3) and R,R-DA (compound 4), were successfully prepared. Compounds 1–4 crystallized in chiral space groups (noncentrosymmetric space groups). The characterization and theoretical calculations were carried out on these four crystal materials, such as the cut-off wavelength, the UV–Vis–NIR absorption, the thermogravimetric analysis, the second harmonic generation (SHG) efficiency of the powdered compounds, the frontier molecular orbital (HOMO and LUMO) energies and the static first molecular hyperpolarizabilities. All of these results imply that compounds 1–4 are desirable candidates for non-linear optical applications.