Tunable Chromic Properties of Viologen‐Metal Polymers Modulated by Coordination Modes for Inkless Erasable Printing

Abstract

Inkless and erasable printing (IEP) based on chromic materials holds great promise to alleviate environmental and sustainable problems. Metal‐organic polymers (MOPs) are bright platforms for constructing IEP materials. However, it is still challenging to design target MOPs with excellent specific functions rationally due to the intricate component‐structure‐property relationships. Herein, an effective strategy was proposed for the rational design IEP‐MOP materials. The stimuli‐responsive viologen moiety was introduced into the construction of MOPs to give it potential chromic behaviors and two different coordination models (i.e. bilateral coordination model, M1; unilateral coordinated model, M2) based on the same viologen ligand were designed. Aided by theoretical calculations, model M1 was recommended secondarily as a more suitable system for IEP materials. Along this line, two representative viologen‐ZnII MOPs 1 and 2 with models M1 and M2 were synthesized successfully. Experiments exhibit that 1 does have quicker stimuli response, stronger color contrast and longer radical lifetime compared to 2. Significantly, the obtained 1‐IEP media brightly inherits the excellent chromic characteristics of 1 and the flexibility of the paper at the same time, which achieves most daily printing requirements, as well as enough resolution and durability to be used in identification by smart device.

Series of Viologen-Based Metal–Organic Polyhedra with Photo/Electrochromic Behavior for Inkless Printing and UV Detection

“…The charge of the discrete cationic [M 2 L 4 ] 6+ barrel is balanced by 4.2Cl – and 1.8NO 3 – , 2.5Cl – are confined within the molecular cage, and the remaining Cl – anions are connected to the barrel via hydrogen bonding. Notably, the shortest distance between the center of a pyridinium ring and chloride anion reaches 3.22 Å, which is consistent with other viologen–chloride distances. − Finally, these cation MOPs are packed with each other in an offset fashion based on H-bonding among Cl – or NO 3 – anions and terminally coordinated H 2 O molecules (Figure f).…”

A Series of POM–Viologen Photo-/Electrochromic Hybrids and Hydrogels Acting as Multifunctional Sensors for Detecting UV, Hg2+, and Organic Amines

“…All three compounds are POM-based compounds constructed by viologen ligand. Therefore, the photochromic properties of three compounds were investigated. − After exposure to a Xe lamp with a filter (300–400 nm), compound 1 showed a visible color change from white to black within 2 min (Figure a). Compound 2 changed from pink to gray after 3 min of irradiation (Figure S8).…”

Four POM-Viologen Color-Changing Materials with Fast Color Response under Various External Stimuli

“…According to previous reports, we have developed a similar ink-free printing paper. Bulk crystals 1 and 2 (25 mg) were respectively ground into powders and dissolved in 10 mL of ethanol. , Sonicate the solution above for 30 min, coat the supernatant on filter paper, and dry it in an oven at 45 °C. The paper for ink-free printing was obtained.…”