Two new photochromic supramolecular compositions based on viologen: photocontrolled fluorescence, aniline detection and inkless erasable printing performance

Two multifunctional supramolecular components synthesized by two different viologen ligands and pyromellitic acid.

Metal-dependent photochromic performance in two isostructural supramolecular chains

The introduction of nonphotochromic coplanar 1,10-phenanthroline into a metal carboxylate system produces two isostructural supramolecular chains with metal-dependent photochromic performance.

Two viologen-based photoluminescent compounds: excitation-wavelength-dependent and photoirradiation-time-dependent photoluminescent switches

We synthesized two isostructural multi-coloured photoluminescent coordination polymers. They exhibit excitation-wavelength-dependent photoluminescence emission and photoirradiation-time-dependent photoluminescence emission in solid-state.

Photochromic and photocontrolled luminescent rare-earth D–A hybrid crystals based on rigid viologen acceptors

Due to the introduction of a strong electron donor, CoIII(CN)63−, into the structure, the rare-earth donor–acceptor (D–A) hybrid crystal shows enhanced photochromism. The coordinative Eu3+ cation is also beneficial toward improving the luminescence.

Robust pyridylbenzoate metal–organic frameworks as sorbents for volatile solvents and gases

Double-walled pyridylbenzoate MOFs display an order/disorder phase transition on solvation/desolvation. This allows the MOFs to retain structural integrity over multiple sorption cycles.

Metal-dependent photosensitivity of three isostructural 1D CPs based on the 1,1′-bis(3-carboxylatobenzyl)-4,4′-bipyridinium moiety

The comparison of the photochromic behaviors of three CPs indicates that metal ions play an important role in regulating their photochromic properties.

The photochromic behaviour of two viologen salts modulated by the distances between the halide anions and the cationic N atoms of viologen

In recent years, viologens and their derivatives have received much attention due to their various potential applications, ranging from electro- or photochromic devices to clean energy. Generally, viologen compounds exhibit a colour change upon being subjected to an external stimulus. However, the chromic mechanism is still ambiguous, because there are many electron-transfer pathways for a chromic compound that need to be considered. Thus, exploring new chromic viologen-based compounds with one pathway should be important and meaningful. In this article, two new viologen-based derivatives, namely 1-(2-cyanobenzyl)-4,4′-bipyridinium chloride (o-CBbpy·Cl), C18H14N3 +·Cl− (1), and 1-(2-cyanobenzyl)-4,4′-bipyridinium bromide (o-CBbpy·Br), C18H14N3 +·Br− (2), have been synthesized and characterized. Interestingly, both isomorphic compounds possess only one electron-transfer pathway, in which 1-(2-cyanobenzyl)-4,4′-bipyridinium cations (o-CBbpy) and halide anions are employed as electron donors and acceptors, respectively. Salts 1 and 2 consist of o-CBbpy cations involved in π–π interactions and hydrogen-bond interactions, and halide anions weakly hydrogen bonded to the viologen cations. The salts show different photoresponsive characteristics under identical conditions, which should be mainly related to the distances between the halide cations and the cationic N atoms of o-CBbpy but not the electronegativities of the halogen atoms. These results should not only help in understanding that the distance of the electron-transfer pathway plays an important role in viologen-based photochromism, but should also guide the design and synthesis of additional photochromic materials.

Photochromic properties of three 2D MOFs based on 1-carboxyethyl-4,4'-bipyridinine

Viologen units have been widely used to impart metal-organic frameworks (MOFs) with photochromic properties. However, construction of a stable photochromic system in viologen MOFs has not been fully explored. Herein, we report three examples of MOFs, namely, {[Cd(CEbpy)(m-BDC)(DMF)]·2H2O} n (1), {[Cd(CEbpy)(p-BDC)(H2O)]·H2O} n (2), and {[Zn(CEbpy)(p-HBDC)(p-BDC)0.5]·H2O} n (3) based on benzenedicarboxylic acids (m-H2BDC = 1,3-benzenedicarboxylic acid, p-H2BDC = 1,4-benzenedicarboxylic acid) and a viologen-derived ligand 1-carboxyethyl-4,4'-bipyridine (L = CEbpy). As expected, the incorporation of the viologen unit into the frameworks results in the predefined photochromism upon both sunlight and UV-light. Compounds 1-3 feature a two-dimensional (2D) layered structure and are all photochromic due to the formation of CEbpy radicals by photoinduced electron transfer (PET). The aggregates build an interesting stable crystalline framework that exhibits long-lived color constancy in the solid state.

Photochromic Lanthanide(III) Materials with Ion Sensing Based on Pyridinium Tetrazolate Zwitterion

Lanthanide(III) ion (Ln(III)) sensing has become a major research area owing to its intriguing prospect in clinic, biology, and environmental studies. However, the existing methods have limitations like requirement of expensive instrumentation, long analytical times, and sample pretreatments, revealing the necessity of other methods. In this work, by using N-methyl-4-pyridinium tetrazolate (mptz) zwitterion as an electron acceptor, we obtained several new Ln(III) compounds with electron-transfer (ET) photochromic properties: [Ln(NO₃)₃(H₂O)₄]·mptz [Ln = Sm (1), Eu (2), Gd (3), La (4), Ce (5), Pr (6), Nd (7), Tb (8), Dy (9), Ho (10), Er (11), Tm (12), Yb (13), Lu (14)]. Notably, different Ln(III) ions in these compounds can be visually identified by their different photoinduced color changes related to the ET process. This work may not only contribute to the more understanding of the structure-photosensitivity relationships of pyridinium-based compounds, but also provide a new approach for Ln(III) ion sensing.

Three viologen-derived Zn-organic materials: photochromism, photomodulated fluorescence, and inkless and erasable prints

Three zinc–viologen materials exhibit reversible photochromism, photomodulated fluorescence and the capability as inkless and erasable print media.

Photochromism of supramolecular assemblies based on benzenecarboxylate donors and viologen acceptors

Similar viologen acceptors, a regular change in donor moieties and photochromism provide an ideal model for elucidating D–A matching rules.

Effect of counter cations on the photochromic behaviors of three Zn–viologen complexes

Similar viologen cations, regular change in acceptor moieties and photochromism provide an ideal model for elucidating D–A matching rules.

Halogen-dependent photoinduced electron transfer and chromism of three protonated nicotinohydrazide halozincates

Three isostructural halozincates, [HNH][ZnX₄]·H₂O (HNH²⁺ = protonated nicotinohydrazide, X = I (1), Br (2), Cl (3)), have been synthesized and exhibit halogen-dependent photoinduced electron transfer and chromic properties. Due to the different electron-donating nature of halogen atoms, only iodozincate hybrid 1 can easily undergo photoinduced electron transfer and eye-detectable photochromic behavior, revealing a unique matching rule between a moderate electron acceptor and halozincates.

Five monocyclic pyridinium derivative based halo-argentate/cuprate hybrids or iodide salts: influence of composition on photochromic behaviors

Using novel monocyclic pyridinium derivatives as structural directing agents and electron acceptors, five composition dependent photochromic compounds have been synthesized.

Exploring the syntheses, structures, topologies, luminescence sensing and magnetism of Zn(ii) and Mn(ii) coordination polymers based on a semirigid tricarboxylate ligand

Two Zn(ii)-CPs and two Mn(ii)-CPs were constructed from metal salts, H₃cpota and N-heterocyclic group ligands. Their structures, magnetic properties and luminescence sensing properties have been studied in detail.

Photochromic and photomodulated luminescence properties of two metal–viologen complexes constructed by a tetracarboxylate-anchored bipyridinium-based ligand

Photochromic and photomodulated luminescence properties of two metal–viologen complexes constructed using a tetracarboxylate-anchored bipyridinium-based ligand are reported.

Indium-based metal–organic frameworks as catalysts: synthesis of 2-nitro-3-arylimidazo[1,2-a]pyridines via oxidative amination under air using MIL-68(In) as an effective heterogeneous catalyst

The metal–organic framework MIL-68(In) has emerged as a productive heterogeneous catalyst for the synthesis of 2-nitro-3-arylimidazo[1,2-a]pyridines via oxidative amination between 2-aminopyridines and nitroalkenes using air as an oxidation agent.

Anion-controlled photochromism of two bipyridinium-based coordination polymers and nondestructive luminescence readout

The first Zn-based coordination polymer constructed with a bipyridinium-functionalized m-benzenedicarboxyl ligand has been synthesized, which can show dual luminescence responses to light in different spectral regions to render nondestructive luminescence readout.

Two photochromic methylated nicotinohydrazide iodoargentate hybrids

Two methylated nicotinohydrazide iodoargentate hybrids have been synthesized via modulating organic/inorganic ratio, which exhibit rare structure-dependent electron-transfer (ET) photochromism.

Stoichiometry-controlled structural and functional variation in two photochromic iodoargentates with a fast and wide range response

Two MCMP⁺/iodoargentate hybrids have been synthesized and they exhibit rare electron transfer photochromsim with a fast response rate, a wide response range and a long-lived charge-separated state, which is largely ascribed to the flexible aggregation of electron-deficient MCMP⁺ counterions.