Effect of intermolecular interaction of the charge-transfer complex between molecular tweezers and C60/C70 on second-order nonlinear optical properties

To enhance understanding of the correlation between the intermolecular interaction and second-order nonlinear optical (NLO) properties, we studied a molecular tweezer with two corannulene substituents linked by a tetrahydro[5]helicene imide, which enabled highly sensitive and selective complexation of C-60/C-70 through convex-concave pi-pi interactions. The geometric structure, molecular orbitals, intermolecular interactions, electron absorption spectra and second-order NLO properties of the charge-transfer (CT) complexes formed by molecular tweezers and C-60/C-70 were studied by density functional theory. Larger fullerenes helped to increase the intermolecular interaction and CT, thereby increasing the first hyperpolarizabilities of CT complexes. Embedding of lithium ions helped to enhance the electron-absorption ability of fullerenes, thereby increasing the intermolecular interaction and intermolecular CT and, thus, enhancing their first hyperpolarizability significantly. Our data indicated that, through structure adjustment (including increasing the volume of fullerene and embedding alkali metal ions), we could enhance intermolecular interactions and improve intermolecular CT significantly. These actions could improve the second-order NLO properties of CT complexes.

Automated summary

The correlation between intermolecular interaction and second-order nonlinear optical (NLO) properties was investigated by studying a molecular tweezer with corannulene substituents linked by a tetrahydro[5]helicene imide. Density functional theory was employed to study the geometric structure, molecular orbitals, intermolecular interactions, electron absorption spectra, and second-order NLO properties of the charge-transfer complexes formed by the molecular tweezers and C-60/C-70.