Theoretical study of the relationships between the molecular structures and the molecular polarizabilities of the donor–acceptor cumulenes and a comparison with the corresponding polyenes

Abstract

AM1 calculations are performed to study the molecular structures and the linear and nonlinear polarizabilities of the donor–acceptor cumulenes under the influence of an external electric field defined by point charges (Sparkles). We investigate the relationships between the molecular structures and the molecular polarizabilities of the substituted cumulenes and compare these with that of the corresponding polyenes. The results show that the relative sizes of the molecular polarizability values for the two molecules depend on the selection of the donor–acceptor pair. We also employ the structure–property relationships to discuss certain trends for the two molecules. It is found that so long as the donor and acceptor pair are appropriately selected, the substituted cumulenes should always have larger hyperpolarizabilities than the corresponding polyenes with chain extension, moreover, the increasing extent of the hyperpolarizabilities for the substituted cumulenes is far larger than that for the corresponding polyenes. These properties make the cumulenes interesting candidates for applications in nonlinear optics, particularly in the area of poled polymer films.