Electronic structure and second-order nonlinear optical property of chiral peropyrenes.

Discovery of novel materials with excellent second-order nonlinear optical (NLO) properties is a very attractive topic in chemistry and materials science. Recently, much more attention has been paid to chiral compounds due to their inherent asymmetric structure and intramolecular charge transfer. Currently, the density functional theory (DFT) has become a powerful methodology to rationalize experimental observations and to design new materials with desirable properties. In this work, on the basis of the reported chiral peropyrene, we designed another five compounds consisting of donor or acceptor moieties and the donor/acceptor combinations. We systematically studied their geometrical/electronic structures and electronic transition/second-order NLO properties. The measured UV-Vis/CD spectra of compound 1 are almost reproduced by our calculations, enabling us to assign its electronic transition property and absolute configuration. For these compounds, the different substituents have great effect on their photophysical properties (i.e., band gap, absorption wavelength, and NLO response). The charge transfer synergy provides some useful information for further performance improvement. Interestingly, compound 6 shows a remarkably large first hyperpolarizability value of 18.14 × 10