Nonlinear optical properties of dihydrobenzothiazolylidene and dihydroquinoinylidene compounds

• First hyperpolarizabilities of four dyes were studied by DFT and CDD analysis.
• BTZ can form an effective push–pull system with acceptor (TCF).
• Larger first β come from larger dipole moment variation and low TE.
• Enhancement of charge transfer with the increase of electric field was found.
• TPA section was firstly studied to explore its potential application in TPA materials.

The geometrical parameters, absorption spectra and first hyperpolarizability of BTZ (12a, 12c) and QUIN (13a, 13c) compounds have been studied with quantum chemistry methods. The hyperpolarizability β and transition energy were determined by density functional theory (DFT) and time-dependent DFT (TD-DFT). Electric field was considered to study the dependence of transition energy on electric field and to fit state-to-state dipole moment. DFT calculation and visualized methods (charge different density and molecular orbital analysis) provided an insight into the relationship between structure and first hyperpolarizability. In addition, two-photon absorption character of them has been firstly studied with the response theory approach. Results demonstrated that 12c and 13c with same electron-withdrawing substitution display obvious nonlinear optical response, and larger value of two-photon absorption sections suggest that they are good candidates for NLO materials.

Charge difference density of BTZ compound with the increase of electric field.Figure optionsDownload high-quality image (68 K)Download as PowerPoint slide