Self-recovery ultraviolet-sensitive photochromic naphthalenediimide based coordination networks: Rapid fluorescence recognition of p-substituted nitrobenzenes

Naphthalenediimide (NDI) derivative has attracted extensive attention because of its photoresponse properties. Here we report a series of novel transition metal coordination networks (CNs): Co-CMNDI, Ni-CMNDI, and Cu-CMNDI, which are constructed by N, N’-bis(carboxymethyl)-1, 4, 5, 8-naphthalenediimide (H2CMNDI) and the corresponding metal salts. The structures are characterized in detail by the microanalysis tools. Structural analysis shown that frameworks of Co-CMNDI and Cu-CMNDI are 3-periodic fsc net features, while Ni-CMNDI is the 2-periodic sql net. They are sensitive to ultraviolet, as well as their color can be changed with the change of radiation time or radiation intensity. The reversibility of their photochromic behaviors and the positive correlation between color change and ultraviolet intensity make them be possible as UV colorimetric cards in the future. Besides, three CNs can be used as a fluorescence recognizer of three nitroaromatics: p-nitroaniline (PNA), p-nitrophenol (PNP), and p-dinitrobenzene (PDNB) by two emission peaks. At the same time, we introduce a concept of quenching recognition constant (KQR), which can better compare the recognition effect of the recognizer. The competitive absorption and photo induced electron transfer between analytes and recognizer are the main reasons for fluorescence quenching. This work provides a novel design idea and materials for future multi-functional sensors