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 (NO 3 ) 1.5 (H 2 O) 7 ]·Cl 4.2 ·(NO 3 ) 0.3 ·H 2 O} n ( 1 ), {[Dy 2 (bcbp) 4 (H 2 O) 8 ]Cl 6 } n ( 2 ), and {[Eu 2 (bcbp) 4 (H 2 O) 10 ]Cl 6 ·H 2 O} 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.