A Photo‐Responsive Charge‐Assisted Hydrogen‐Bonded Organic Network with Ultra‐Stable Viologen Radicals

Abstract

Comprehensive Summary Hydrogen‐bonded organic networks (HONs) have attracted intense research interest due to their mild synthesis conditions, good solvent processability and strong reproducibility. Most HONs are constructed by electrically neutral organic ligands through intermolecular interactions such as weak hydrogen bonding, π‐π stacking. But there are a few charge‐assisted hydrogen‐bonding networks (CAHONs) constructed by oppositely charged organic components. Under hydrothermal conditions, we successfully synthesized a 3D CAHON (H2CV)(H2BTEC) (1) constructed by H2CV (CV = N,N′‐4,4′‐bipyridine dipropionate) and H4BTEC (H4BTEC = 1,2,4,5‐benzenetetracarboxylic acid) through multiple charge‐assisted hydrogen bonding. Upon soft X‐ray, ultraviolet light or sunlight irradiation under ambient conditions, 1 quickly changes from colorless to blue (1P), and kinetic calculations show that its photochromism meets first‐order dynamics. Interestingly, the colored crystals 1P with long‐lived colored radicals will not fade after being placed for more than two months at room temperature in air, owing to the fact that the photogenerated viologen radicals can be stabilized by the abundant hydrogen bonds, the coplanar pyridinium rings and the slow electron‐hole recombination. Moreover, 1 is a typical direct band gap semiconductor, evidenced by the calculated band gap of 3.24 eV, in agreement with the experimental value of 3.40 eV. In view of its strong colored stability, 1 is designed for distinctive inkless printing.

Hydrogen‐Bonded Engineering Enhancing Phase Transition Temperature in Molecular Perovskite Ferroelastic

“…[ 31 ] Therefore, compound 1 has an enhancement of T r about 71 K (the higher temperature T 2 should be similar to the case of lower T 1 ) by the introduction of hydrogen bond, which is larger than most compounds with H/F substitution or deuterium effect enhanced value of T r . [ 38‐42 ] This is a successful example to optimize performance by hydrogen bonding engineering in cage perovskite.…”

Applications of Viologens in Organic and Inorganic Discoloration Materials

“…(b) Diagram to show the interpenetrating mode of the supramolecular networks [44] . (c) 3D supramolecular organic structure with 1D channels occupied by H 2 BTEC anions [45] . Reprinted with permission from Ref.…”

“…Reprinted with permission from Ref. [44] (Copyright 2014, Royal Society of Chemistry), [45] (Copyright, 2022,Wiley Online Library).…”

“…Similarly, Zhang's group also synthesized the D−A system. Their electron donor of choice was 1,2,4,5‐benzenetetracarboxylic acid (H 4 BTEC) [45] . The difference is that the selected viologen is N, N′‐4,4′‐bipyridine dipropionate (CV).…”

A series of naphthalenediimide-based metal–organic frameworks: synthesis, photochromism and inkless and erasable printing

“…1,2 Inkless and erasable printing as a new alternative technology has attracted extensive attention for zero printing ink, low energy consumption and reusable printing paper. 3–7 However, searching for materials that can be applied in inkless and erasable printing remains a huge challenge.…”