AM1 study of the relationship between the donor–acceptor strength and the polarizabilities of push–pull polyenes

Abstract

AM1 calculations are performed to study the non-linear optical properties of push–pull polyenes. On adopting different donor and acceptor groups in hexatriene a set of hexatriene derivatives is obtained whose bond length alternations (BLA) are calculated to be −0.070 to 0.110 Å, ranging from a charge-separated form to a neutral polyene form. Another parameter, δ_DA′ is also introduced to characterize the effectiveness of donor–acceptor pairs. The relationships between the polarizabilities and δ_DA′ or BLA are investigated, giving an insight into the electronic origin of the linear and non-linear responses of these donor–acceptor substituted polyene molecules. The results may provide structural guides on selecting donor and acceptor groups for synthesizing molecules with desired non-linear optical (NLO) properties.