Orbital Control of the Conductance Photoswitching in Diarylethene

Diarylethenes are photosensitive π-conjugated molecules whose application to various molecular devices is expected. The molecular and electronic structures of diarylethenes are switchable upon photoirradiation with their reversible structural isomerization. Site-specific electron transport phenomena through a diarylethene molecule, 1,2-di(2-methyl-1-naphthyl) perfluorocyclopentene, are studied by using the nonequilibrium Green’s function method combined with the Hückel molecular orbital method (NEGF−HMO) and density functional theory (NEGF−DFT). On the basis of the orbital symmetry rule, the conductance of the diarylethene is predicted to be efficiently switchable when the C3 and C10 atoms are appropriately connected with electrodes. Transmission spectra, spatial distribution of the MPSH (molecular projected self-consistent Hamiltonian) states, and I−V curves are obtained from DFT calculations. These results obtained from the higher-level DFT calculations are consistent with the prediction based on the qualitative frontier orbital analysis at the HMO level of theory. The computed current for the closed-ring form of the 3-10 connection is about 3 orders of magnitude high compared with those for other connections. The phase, amplitude, and spatial distribution of the frontier orbitals play an essential role in designing the electron transport properties through the photoswitching system.