Abstract: This paper presents the results of calculations on the first hyperpolarizability and molecular frontier orbital properties of hemicyanine derivatives by the finite-field (FF)/ PM3 method. It is evident that the first hyperpolarizability tensor of hemicyanine derivatives strongly depends on the D-π-A electronic structure of the molecule, but not sensitive to the σ-alkyl chain length. The HOMO-LUMO calculations reveal that the first hyperpolarizability of these derivatives is linearly related to the HOMO-LUMO energy gap ΔEHL.

Key words: Nonlinear optics, Hemicyanine, First hyperpolarizability, Molecular frontier orbital