[reaction: see text]. Electrochemical oxidation of diarylethene derivatives induced cyclization or cycloreversion reactions. The reaction mechanism was studied with CV, absorption spectra, and theoretical calculation.

The roughness and cleanness of a titanium surface must be controlled in order to investigate the expression mechanism of hard tissue compatibility on titanium. In this study, osteogenic MC3T3-E1 cells were cultured and differentiation-induced on bulk and sputter-deposited titanium specimens, and the osteogenesis were investigated. For the preparation of bulk specimens, titanium discs were mirror-polished. On the other hand, titanium was sputter-deposited on smooth and clean cover glasses as sputter-deposited specimens. As a result, no significant difference was observed in the cell morphology and attached number. On the other hand, the time showing maximum activity in the alkaline phosphatase and gene expressions, which are related to bone differentiation on the bulk titanium, were superior to those on the sputter-deposited titanium. From the surface observation of the specimens with a scanning electron microscope and a scanning probe microscope, the surface on the sputter-deposited titanium was more uniform and cleaner than that on the bulk titanium. According to X-ray photoelectron spectroscopy, the thickness of surface oxide film on the sputter-deposited titanium was smaller than that on the bulk titanium. In addition, the proportions of TiO and Ti(2)O(3) in the surface oxide film on the sputter-deposited titanium were larger than those on the bulk titanium. These differences might influence the differentiation of osteoblastic cells.

The ESR spectrum of a diarylethene was measured during electrochemical oxidative ring-opening reaction of the closed-ring isomer. The spectrum was simulated by UB3LYP/cc-pVTZ method to reveal that the spectrum contains the cation radicals of both the open- and closed-ring isomers. By comparing the calculated spectrum with the experimental one, the ratio between the cation radical of the open- and the closed-ring isomers was determined to be 4:1.