Photo/Electrochromic Dual Responsive Behavior of a Cage-like Zr(IV)-Viologen Metal–Organic Polyhedron (MOP)

Abstract

Stable stimulus-responsive materials are highly desirable due to their widespread potential applications and growing demand in recent decades. Despite the fact that viologen derivatives have long been known as excellent photochromic and electrochromic materials, the development of stable viologen-based multifunctional smart materials with short coloration times remains an exciting topic. To obtain photochromic and electrochromic dual responsive materials, embedding the viologen ligand into a robust metal oxide cluster to increase its stability and sensitivity is an effective strategy. Herein, a viologen-based metal–organic polyhedron (MOP) {[Zr6L3(μ3-O)2(μ2-OH)6Cp6]·8Cl·CH3OH·DMF} [Zr-MOP-1; H2L·2Cl = 1,1′-bis­(4-carboxyphenyl)-4,4′-bipyridinium dichloride, and Cp = η5-C5H5] was successfully prepared and characterized. It consists of trinuclear Zr–oxygen secondary building units and exhibits reversible photochromic and electrochromic dual responsive behaviors. As expected, the designed robust viologen-based nanocage with a V2E3 (V = vertex, and E = edge) topology can maintain its stability and rapid photo/electrochromic behaviors with an obvious reversible change in color from purple (brown) to green, mainly due to the enclosed cluster structure and the abundant free viologen radicals that originate from the effective Cl → N and O → N electron transfers. Spectroelectrochemistry and theoretical calculations of this Zr-MOP were also performed to verify the chromic mechanism.

Applications of Viologens in Organic and Inorganic Discoloration Materials

“…[61] (h) 3D packing pattern and special pore structure of the inherent cavity of Zr-MOP-1. [62] Reprinted with permission from Ref. [54] (Copyright 2010, Royal Society of Chemistry), [56] (Copyright 2018, American Chemical Society), [57] (Copyright 2017, American Chemical Society), [58] (Copyright 2017, Wiley Online Library); [59] (Copyright 2019, Royal Society of Chemistry), [60] (Copyright 2020, Royal Society of Chemistry), [61] (Copyright 2019, American Chemical Society), [62] (Copyright 2021, American Chemical Society).…”

“…Six bpdos are used as linkers to connect each Y 2 O 12 unit with the adjacent 4 units to form a 2D layer, and further build a 3D network by bridging bpdo (Figure 4g). Zang's group synthesized a viologen‐based metal‐organic polyhedron (MOP) in 2021 [62] . They chose 1,1′‐bis(4‐carboxyphenyl)‐4,4′‐bipyridinium dichloride (H 2 L ⋅ 2Cl) as ligand, and ZrCp 2 Cl 2 (Cp=η 5 ‐C 5 H 5 ) as metal salt.…”

“…Zang's group synthesized a viologen-based metal-organic polyhedron (MOP) in 2021. [62] They chose 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium dichloride (H 2 L • 2Cl) as ligand, and ZrCp 2 Cl 2 (Cp = η 5 -C 5 H 5 ) as metal salt. Discrete cage-like complex with V 2 E 3 topology is formed by carboxylic acid groups in the ligands bridging two trinuclear {Zr 3 (μ 3 -O)(μ 2 -OH) 3 Cp 3 } SBUs with three ligands, and these trinuclear cluster-based cages are stacked on each other in an offset manner (Figure 4h).…”

“…(g) Encapsulation of 1D (Pb 2 I 4 Br 3 ) n 3nÀ chain into a [(Pr(bpdo) 4 (H 2 O) 2 ] 3 + quasi-3D network showing hydrogen bonds [61]. (h) 3D packing pattern and special pore structure of the inherent cavity of Zr-MOP-1 [62]. Reprinted with permission from Ref [54].…”

Large Room Temperature Magnetization Enhancement in a Copper-Based Photoactive Metal–Organic Framework

“…Photochromism, with reversible color changes in materials under the irradiation of light, has potential applicability in optical switches, data storage, chemical sensors, etc. − Growing interest in this field has expanded the research of syntheses, properties, and multiple responses of these photochromic materials. − Until now, various types of photochromic systems have been achieved based on diarylethenes, spiropyrans, naphthalenediimides, and azo and viologen derivatives involving cis–trans isomerization, ring opening/closing, or electron-transfer mechanisms. − Among them, the representative photochromic viologen derivatives have been widely utilized to construct the electron-transfer photochromic architectures. − However, research on these photochromic materials constructed by new photoactive ligands is still limited. , …”