Detailed electrochromic properties including the microkinetic switching behaviour of 2-nitro- (P1) and 2,8-dinitro-5a-[2-(4-dimethylaminophenyl)ethylene]-6,6-dimethyl-5a,6-dihydro-12H-indolo[2,1-b][1,3]benzooxazine (P2) were investigated in both solution and indium tin oxide (ITO) devices with a dual-wavelength time-dependent spectra monitoring method for the first time. These two oxazine derivatives displayed improved fatigue resistance and colour reversibility towards electrical stimulation compared with conventional spiropyran derivatives. A new electrochromic mechanism was proposed based on the experimental results and on quantum chemical calculations. Owing to an electron-withdrawing group para to the nitrogen of the indole fragment, P2 demonstrates better electro-driven reversibility of structural transformation between ring-open and ring-closed isomers than P1.

Theoretical investigation of the polarization effect on a potential single-molecule transistor has been studied with density functional theory. 4,4′-(2-Amino-5-nitro-1,4-phenylene)bis(ethyne-2,1-diyl) dibenzenethiol (AN-OPE), containing a donor and an acceptor (D–A) crossed to its oligo(p-phenylene-ethynylene) (OPE) backbone, was used as a prototype for this study. Simulation results indicate that AN-OPE has a higher on/off ratio on conductance than OPE because of the larger polarization along the D–A direction. This high on/off ratio was proved by the 20 times variation in molecular charge, 15 times variation in bond lengths, 49 times variation in polarizability, 9 times variation in the rotation angles, and 13 times variation in the highest occupied molecular orbital–lowest unoccupied molecular orbital gaps under the same gate using B3LYP/6-31G (d, p). And results imply that conjugated molecules with a cross D–A structure could be a good direction for constructing a better single-molecule field-effect transistor. Copyright © 2014 John Wiley & Sons, Ltd.