Photoinduced electron transfer reactions across rigid linear spacer groups of high symmetry

Abstract

A series of highly symmetrical dienes 1– 3 were prepared through [2+2] cyclo-addition of norbornadiene (NBD) in an exo– trans– exo geometry. These molecules can be utilized as spacer groups in donor(D)–spacer(S)–acceptor(A) types of electronic dyads possessing strictly linear rigidity. The electronic coupling between D and A was promoted effectively by the σ-bonds through the all- trans spacer groups so that a highly efficient photoinduced electron transfer process takes place. The even–odd NBD dependent alternation of the D/A orientation is intriguing, which leads to an unusual correlation in the spacer tuning electron transfer process.