Design of a new dihedral-angle-controlled molecular scissors: A DFT investigation

Abstract

DFT calculations are employed to investigate the effects of the addition of a photoisomerizable stilbene unit to Aida′s molecular scissors on relative energies, dipole moments, and kinetic stability according to HOMO-LUMO energy gaps and amplitude of the open-close motion of blade moieties. The most obvious finding emerging from this study is the coming into existence of a new pair of molecular scissors operated by two photoswitchable units. Based on photoisomerization of azobenzene and stilbene units, four conformations appear for these new molecular scissors: cis–cis, cis–trans, trans–cis, and trans–trans. The HOMO-LUMO energy gaps promise that all isomers are kinetically stable. The other important finding is that in these new molecular scissors the dihedral angle between the two blade moieties can be controlled and measured through the open-close motion and the blade parts can adopt two middle states in addition to open-close forms.