Theoretical Investigation on Structures and Nonlinear Optical Properties of the Alkalis and Low Coordination Acenes Salt

The alkalis and low coordination acenes salts α-M@n-acenes (M = Li, Na and K) salts (n = 1, 2 and 3) were designed to investigate the effect of the increasing atomic number of alkali metals and the number n of conjugated benzenoid rings on the nonlinear optical responses. Alkalis Li, Na and K were selected herein, and both DFT (M05-2X, M06-2X and PBE0) and MP2 methods and 6-311+G(D) basis set are employed to optimize geometrical structures and to calculate the polarizability (α0) and first hyperpolarizability (βvec) of the α-M@n-acenes (M = Li, Na and K) salts (n = 1, 2 and 3). Results show that the α0 values of α-M@n-acenes (M = Li, Na and K) salts (n = 1, 2 and 3) increase with increasing number of n conjugated benzenoid rings and the atomic number of alkali metals and βvec values of α-M@n-acenes (M = Li, Na and K) salts (n = 1, 2 and 3) are opposite. The βvec values of α-M@n-acenes (M = Li, Na and K) salts (n = 1, 2 and 3) are inceasing remarkably (397.6 au. for α-Li@ benzene < 1196.5 au. for α-Na@benzene < 1608.6 au. for α-K@benzene and tending to decease with increasing number of n by M06-2X method. Our present research may be favorable to the development of excellent nonlinear optical (NLO) materials.

Wenmin XIAO and Dongmei LUO