Linear and Nonlinear Optical Properties of Triphenylamine-Indandione Chromophores: Theoretical Study of the Structure-Function Relationship under the Combined Action of Substituent and Symmetry Change.

Linear and nonlinear optical properties of experimentally synthesized triphenylamine-indandione chromophores were investigated by time-dependent density functional theory calculations. The absorption and emission spectra, as well as the static and dynamic first hyperpolarizabilities related to the combined effect of substituent introduction and symmetry breaking, were discussed in detail. Theoretical analysis indicated the uniting of indandione acceptor group(s) with a precursor (triphenylamine, TriPhA), with the molecular symmetry destroyed simultaneously, leads to an obvious change in both the peak position and intensity of the linear spectra. The same process can also substantially magnify the molecular first hyperpolarizabilities. The triphenylamine-indandione molecules exhibit efficiencies in static first hyperpolarizability relative to that of the electron-donating TriPhA component and the electron-accepting indandione moiety. The optical nonlinearity would be further expanded under the influence of a resonance effect induced by appropriate excitation. Incident light with a wavelength nearly two times the one-photon absorption is likely to cause a greater frequency dispersion response. In particular, the first hyperpolarizabilities of the title compounds can be enlarged by about 3.2 times on average by resonance enhancement at a fundamental wavelength of 1064 nm.