Solvent-Modulated Self-Assembly of Naphthalenediimide-Based Cd(II) Complexes and the Controllable Photochromism via Conformational Isomerization

Abstract

Rational regulation of the properties of photochromic materials is a challenging and meaningful work. In the present work, NDI-based complexes, namely, [Cd0.5(NDI)­(HBDC)]·H2O (1) and a series of conformational isomers of {[Cd­(NDI)0.5(BDC)]·MeCN} n (2), were synthesized by varying the solvent conditions (H2BDC = terephthalic acid, NDI = N,N′-bis­(3-pyridylcarbonylhydrazine)-1,4,5,8-naphthalene diimide). Complex 1 exhibits a 0D mononuclear structure without photochromic behavior due to the bad conjugation of the naphthalene diimide moiety. The conformational isomers of complex 2 manifest a 3D network, showing ultra-fast photo-induced intermolecular electron transfer photochromic behavior under X-ray, UV, and visible light. However, they show different photochromic rates and coloring contrast upon photoirradiation, which originates from their difference in the distances of lone pair­(COO)···π­(NDI). This was realized via controlling the solvent ratio in the reaction system. In addition, compared to UV/X-ray light, 2 exhibits greater sensitivity to visible light and is an organic–inorganic hybrid material with photomodulated luminescence. Based on the excellent performance, complex 2 can be applied to filter paper, showing potential applications as an inkless printing medium and selective perception of ammonia and amine vapors in the solid state via different visual color changes.

Thermosalient effect of a naphthalene diimide and tetrachlorocobaltate hybrid and changes of color and magnetic properties by ammonia vapor

“…The colored states ( 1_NH 3 , 1_EA , 1_DEA , and 1_TEA ) exhibited a strong ESR signal ( g = 2.0043–2.0049), confirming the presence of the free radicals produced by ammonia and amines as seen in viologen complexes or NDI-based compounds. 6,8 The variation in the ESR signal's width may be caused by contamination resulting from the generation of ammonium salts due to prolonged exposure to amines. The vapochromic phenomenon is essentially attributed to the formation of organic radicals through electron transfer from ammonia or amines.…”

“…3 As a strategy for developing chromic OIMHs, researchers have focused on stabilizing radicals by selecting electron-accepting organic motifs or π-acids, such as viologens, 4 tris(4pyridiniumyl)-1,3,5-triazine (TPT) 5 and naphthalene diimides (NDIs). 6…”

“…OIMHs consisting of electron-acceptors can cause color changes due to the generation of radicals, making them promising candidates for sensing ammonia/amines, which are electron donors. 4–6…”

The modulation effect of auxiliary ligands on photochromic properties of 3D naphthalene diimide coordination polymers

“…S1 †) was prepared as reported by the literature. 38 A 300 W mercury (Hg) lamp (∼365 nm) system with temperature control was employed to prepare colored samples, and the distances between these samples and the Hg lamp were around 25 cm. Thermogravimetric analysis-differential scanning calorimetry (TG-DSC) was investigated in a nitrogen atmosphere (flow rate 100 cm 3 min −1 , heating rate 10 °C min −1 and temperature range of 30-800 °C) using an HCT-2 thermogravimetric analyzer.…”

The effect of conjugation degree of aromatic carboxylic acids on electronic and photo-responsive behaviors of naphthalenediimide-based coordination polymers

“…Organic-inorganic hybrid photochromic systems composed of electron donors (EDs) and electron acceptors (EAs) have attracted a great degree of scientific attention due to their exceptional photo-responsive characteristics (instantaneous photo-responsive rate, wide photo-responsive range and intense coloration contrast) and wide range of application prospects in data storage, optical switches, sensors, protection, inkless printing and so forth. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Some extraordinary achievements have been made in organic-inorganic hybrid photo-chromic materials through ingenious structural design. [18][19][20][21] Especially, the photochromic performances in terms of photoresponsive rate, photo-response range and coloration contrast of these hybrids have been optimized by rational selection and masterly integration of EDs and EAs as well as effectively modulating intermolecular electronic behaviors.…”