The effect of iodide on electronic and photo-responsive behaviors of 1D naphthalenediimide-based zinc coordination polymers

Abstract

Four one-dimensional (1D) naphthalenediimide-based zinc coordination polymers, [ZnI₂(4-PMNDI)] (1), [ZnI₂(3-PMNDI)]₂·DMF (2), [ZnI₂(3-PMNDI)]₂·DMA (3) and [ZnI₂(3-PMNDI)]₂·NMP (4) (4-/3-PMNDI = N,N'-bis(4-/3-pyridylmethyl)-1,4,5,8-naphthalenediimide, DMF = N,N'-dimethylformamide, DMA = N,N'-dimethylacetamide, NMP = N-methyl pyrrolidone) have been synthesized, which exhibit completely different electronic and photo-responsive behaviors. By comparion of the optical inertness of 1, 2-4 exhibit noticeable photochromic behaviors, which is attributed to the usage of 3-PMNDI and consequent the formation of different interfacial contacts of electron acceptors (EAs)/electron donors (EDs) as well as the occurrence of new electron transfer channels (lone pair-π and π-π interactions) in 2-4. Interestingly, the sequential photochromic behaviors of 2-4 (brown to dark brown for 2, light brown to brownish black for 3 and earthy yellow to brownish black for 4) are mainly ascribed to the introduction of different electron-rich solvents, which lead to the slight different interfacial contacts of EAs/EDs. This work provides a new strategy of the manipulation of electronic behaviors from sole intermolecular charge transfer (ICT) to photoinduced intermolecular electron transfer (PIET) and the photo-responsive behaviors from "OFF" to "ON" by adjustion of the interfacial contacts of EAs/EDs for the first time.