Intercalation of cationic azobenzene derivatives in a synthetic mica and their photoresponse

Four types of cationic azobenzene derivatives (Azds) having quaternary ammonium functional group at the 4-position (“single-hand”) or at the 4 and 4′-positions (“double-hand”) were synthesized and intercalated in a synthetic mica, Li taeniolite (LiTN), by ion exchange to obtain photoresponsive complexes. Powder X-ray results suggested that the long axis of molecules was at an angle of 58–62° from the mica layer for the single-hand series and at about 24° for the double-hand series. Photoresponse by ultraviolet (UV) irradiation with λ=365 nm and visible light (VIS) with λ=436 nm was monitored by the change in d(001), the basal spacing. Each Azd/TN complex showed different types of behavior toward UV/VIS irradiation. Complexes of a double-hand azo derivative showed a basal-spacing contraction of 0.7% under UV irradiation, but recovered their initial length under VIS irradiation, or by standing in the dark. Another complex presented a nonreversible change in basal spacing of 4%. This contraction under UV irradiation was attributed to trans-to-cis isomerization of the azobenzene moiety in guests, although the complex interlayer-space environment may have caused a different response after contraction.