The Modulation of Photoinduced Intermolecular Electron Transfer in Naphthalenediimide-Based Photochromic Coordination Polymers
Shimin Zhang, Pengfei Hao, Haiying Yang, Junju Shen, Yunlong Fu
Abstract
The controllability of photoinduced intermolecular electron transfer (PIET) of coordination polymers (CPs) with photochromic performance is of great significance and continues to present a challenge. Here, two naphthalenediimide (NDI)-based photochromic CPs, [Ca(CENDI)(H 2 O)(DMF)] ( 1 ) and [Ca(CPNDI)(H 2 O) 2 ] ( 2 ) (H 2 CENDI = N, N ′-bis(carboxyethyl)-naphthalenediimide and H 2 CPNDI = N, N ′-bis(carboxypropyl)-naphthalenediimide), were obtained via the integration of H 2 CENDI/H 2 CPNDI with Ca 2+ ions, respectively. Interestingly, structural transformation of a single crystal was realized (i.e., a two-dimensional layer for 1 versus a three-dimensional open framework for 2 ) by the increase of length of side chain amino acid groups (β-alanine for 1 versus γ-amino butyric acid for 2 ), which indicates that N -substituents can effectively regulate the single-crystal structures. Meanwhile, 1 and 2 display entirely different photoresponse rate (color transformation time: all are 1 s, Δ abs: 0.30 for 1 versus 0.13 for 2, coloration saturation time: 7 s for 1 versus 1 min for 2 ), indicating that the PIET process could also be effectively regulated by varying the N -substituents. Notably, an effective and easy method for regulating the PIET behaviors of CPs has been developed in this paper, paving the way for the construction of controllable functional materials.