Mechanism of spatially resolved photochemical control of the resistivity of a molecular crystalline solid.

By maintaining α-Ag(DM)(2) (DM = C(10)H(8)N(4)) around room temperature (RT) ([Formula: see text]) during ultraviolet-visible (UV-vis) irradiation, a series of photochemical products named β was obtained. The solid β was comprised of structurally different compounds. All of the solid β phases share the original chemical formula of Ag(DM)(2) and exhibit semiconducting behaviour, yet they differ from each other in their XRD patterns. They are divided into two phases: β1 and β2. Compared with the XRD pattern of the α phase, the β1 phase exhibited XRD peaks at the same 2θ-angles but with different relative intensities, while the β2 phase exhibited totally different XRD patterns from those of the α or β1 phases. The actual composition of a particular solid of 'β' phase is dependent upon irradiation time, and can be controlled continuously. Around RT, the α phase exhibits metallic conductivity, while the β1 and β2 phases are suggested to be semiconductors. As a result, one can continuously and finely control the electrical resistivity of Ag(DM)(2) by UV irradiation to modify it into a mixture of α, β1 and/or β2 phases.