Effective regulation of second-order nonlinear optical properties of macrocyclic thiophene-based derivatives with dipole structure

Abstract The static second-order nonlinear optical susceptibilities (β0) of a series of macrocyclic thiophene-based derivatives with strong donor/acceptor (D/A) substituents were studied in detail on the basis of the stability of the equilibrium geometries calculated at density functional theory (DFT) level. The research results show that the type of substituent, the pair number and the position of D/A group all have important influence on the value of β0. The molecule 4A1–4D5–8 with four pairs of electron donor ( NH2) and acceptor ( CN) located at contraposition has larger value of β0 (−338.88 × 10−30/esu), which is close to 50 times larger than that of SII. And the absolute value of β0 enlarges as increasing the ring size or the pair number. Moreover, the effects of BLA and charge transfer are analyzed to explain the significant enlargement of β0 for the molecules with stronger D/A group, besides the influence factors of ƒ, Δμ and W in the two-level approximation formula. In addition, it indicates an approximately proportional relationship between the values of β0 and δmax for most studied molecules.