Readily accessible rhodamine B-based photoresponsive material

A photochromic rhodamine B-based material containing Cd(II) as bridge was facilely prepared. The 4-methoxylsalicylaldehyde rhodamine B hydrazone Cd(II) complex displayed unusual ring-open response upon 365 nm UV irradiation, exhibiting long photochromic lifetime and good fatigue resistance. The UV-induced ring-open of the complex led to a distinct color and fluorescence change in acetonitrile. A new mechanism was put forward: salicylaldehyde part in the complex underwent UV-promoted isomerization from enol-form to keto-form, enhancing the chelation of Cd(II) and yielding the ring-opening rhodamine B part. Compared to other reported photochromic systems, this new photochromic material offered attractive new insights into the development of low cost photochromic materials with good performance.