External electric field driven conformation of the wing-shaped nanographene to close: enhancing and tuning nonlinear optical properties

Abstract

The nanographene has attracted intensive research interest due to its unique structure and remarkable properties. In the present work, we applied the external electric field (F ± z) to the wing-shaped N-doped nanographene with the bicyclo[2.2.2]-octadiene(BCOD)-bridged bis-hexapyrrolohex-aazacoronene (HPHAC), the BCOD-HPHAC in the direction of the negative and the positive z-axis, respectively. Interestingly, the geometric structures of the BCOD-HPHAC are from patulous to closed under the F ± z, the centrosymmetric symmetry of system is broken. Further, the molecular electrostatic potential (ESP) maps show that the F ± z can effectively regulate the charge distribution of the BCOD-HPHAC. Markedly, the first hyperpolarizabilities (βtot) are regulated efficiently under the F ± z. Compared with the F-z, the Fz induces a larger βtot value of ranging from 2.07 × 102 au (F ± z = 0 au) to 1.01 × 104 au (Fz = 200 × 10−4 au). Moreover, the evolutions of the absorption spectra can explain well the trend of βtot values under the F ± z. We hope that the current work can inspire the investigations of the centrosymmetric nanographenes in the field of NLO response controlled by the external electric field.