Series of Viologen-Based Metal-Organic Polyhedra with Photo/Electrochromic Behavior for Inkless Printing and UV Detection

The fabrication of molecular crystalline materials with fast, multistimuli-responsive behavior and the construction of the corresponding structure-activity relationship are of extraordinary significance for the development of smart materials. In this context, three multistimuli-responsive functional metal-organic polyhedra (MOP), {[Dy-2(bcbp)(3)(NO3)(1.5)(H2O)(7)]<middle dot>Cl-4.2<middle dot>(NO3)(0.3)<middle dot>H2O}(n) (1), {[Dy-2(bcbp)(4)(H2O)(8)]Cl-6}(n) (2), and {[Eu-2(bcbp)(4)(H2O)(10)]Cl-6<middle dot>H2O}(n) (3; bcbp = 1,1 '-bis(4-carboxyphenyl)-4,4 '-bipyridinium), were successfully prepared and characterized. All of the compounds exhibit rapid and reversible photochromic and electrochromic dual-responsive behaviors. Furthermore, benefiting from the well-defined crystal structure and different responsive behaviors, the photoinduced electron transfer (PIET) process and structure-activity relationship were explored. In addition, considering the excellent photochromic performance, function filter paper and smart organic glass were successfully prepared and used for ink-free printing and UV light detection.