Electron-transfer Photochromism Research Articles

Photo-Activating Biomimetic Polyoxomolybdate for Boosting Oxygen Evolution in Neutral Electrolytes.

Inspired by the metal-oxo cluster structural feature and charge separation behaviour of the oxygen evolving center (OEC) in photosystem II (PS-II) under photoirradiation, a new crystalline photochromic polyoxomolybdate, MV2 [β-Mo8 O26 ] (1, MV=methyl viologen cation), is designed as a biomimetic oxygen evolution reaction (OER) catalyst in neutral electrolytes. After photoinduced electron transfer (PIET) with colour change from colourless to grey, it remains in an ultra-stable charge-separated state over a year under ambient conditions. The observed overpotential at 10 mA ⋅ cm-2 and Tafel slope decrease by 49 mV and 62.8 mV ⋅ dec-1 after coloration, respectively. The outstanding OER performance of the coloured state in neutral electrolytes even outperforms the commercial RuO2 benchmark. Experimental and theoretical studies show that oxygen holes within polyanions after irradiation serve as sites for enhancing direct O-O coupling, thus effectively promoting OER. This is the first successful application of electron-transfer photochromism to realize OER activity gain.

Light‐Induced Electron Transfer Toward On/Off Room Temperature Phosphorescence in Two Photochromic Coordination Polymers

AbstractPhotoswitchable room temperature phosphorescence (RTP) materials are of great interest due to their potential applications in optical devices and switches. Herein, two Zn‐based coordination polymers (CPs) (H3‐TPB)·[Zn6(H‐HEDP)(HEDP)3(H2O)2]·5H2O (complex 1; HEDP = hydroxyethylidene diphosphonate; TPB = 1,3,5‐tris(4‐pyridyl)benzene) and (H‐TPB)·[Zn3(H‐HEDP)(HEDP)(H2O)]·2H2O (complex 2) with distinguishable photochromism and tunable RTP are synthesized involving photoactive TPB molecules with different packing modes. Complex 1 exhibits bidirectionally on/off RTP regulation via on‐switch with excitation of 250−330 nm light and off‐switch with 350−380 nm, and the “turn‐on” behavior can be attributed to the advance of Förster resonance energy transfer‐assisted intersystem crossing (ISC) process while “turn‐off” process due to the transformation from H3‐TPB cations to H3‐TPB· radicals. Complex 2 exhibits photoswitchable RTP accompanied with reversible photochromism by leveraging the self‐absorption and RTP emission. Two demos based on the above compounds are further applied to demonstrate the application in information recording and encryption fields. This work supplies a strategy toward the design of switchable RTP systems using electron transfer photochromism, shedding light on broadening the frontiers of photoresponsive materials.

Photochromic, fluorescence modulation and inkless printing of a zinc(II) inorganic–organic hybrid material based on 2,3-pyridinecarboxylic acid

An inorganic–organic hybrid material [Zn(2,3-pydc)(H2O)2]n (1) was synthesized with 2,3-pyridinecarboxylic acid (2,3-H2pydc) and Zn(NO3)2·6H2O by solvothermal method. Compound 1 exhibits reversible photochromism between pale yellow and blue. The electron-transfer photochromism of 1 was verified by UV–vis, EPR and XPS spectra. The electron was transferred from carboxylate to pyridine ring upon irradiation. It is worth noting that unlike the luminescence quenching of normal photochromic materials via photoinduced coloration, the emission intensity of 1 can be obviously enhanced in the process of electron-transfer photochromism. 1 was found to display a long charge-separated state with a lifetime value of more than 6 months, exceeding the most reported values of the analogues. It endows potential to be applied in inkless printing.

Correction to “The Influence of Anions on Electron-Transfer Photochromism of Bipyridinium-Derived Metal–Organic Materials”

ADVERTISEMENT RETURN TO ISSUEPREVAdditions and Correc...Additions and CorrectionsNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “The Influence of Anions on Electron-Transfer Photochromism of Bipyridinium-Derived Metal–Organic Materials”Jian-Jun Liu*Jian-Jun LiuMore by Jian-Jun Liuhttps://orcid.org/0000-0001-9912-5396, Shu-Biao XiaShu-Biao XiaMore by Shu-Biao Xia, Yao LiuYao LiuMore by Yao Liu, Hongbo SuoHongbo SuoMore by Hongbo Suohttps://orcid.org/0000-0002-7102-8874, Jiaming LiuJiaming LiuMore by Jiaming Liu, and Xiang ShenXiang ShenMore by Xiang Shenhttps://orcid.org/0000-0002-0736-905XCite this: Cryst. Growth Des. 2022, 22, 6, 3990Publication Date (Web):April 27, 2022Publication History Published online27 April 2022Published inissue 1 June 2022https://doi.org/10.1021/acs.cgd.2c00442Copyright © 2022 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views159Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (426 KB) Get e-AlertsSUBJECTS:Anions,Materials,Photochromism Get e-Alerts

Effect of positional isomerism on electron-transfer photochromism and photoluminescence of two pyromellitic diimide-based organic molecules

Two positional isomeric organic molecules, 2-PMPMD (1) and 4-PMPMD (2) (2/4-PMPMD = N, N′-bis(2/4-pyridylmethyl)-pyromellitic diimide) have been constructed by anchoring two pyridylmethyl groups at both sides of nitrogen positions in pyromellitic diimide (PMD), which are assembled into different supramolecular architectures through lone pair-π interactions. Noteworthy, 1 and 2 exhibit unique electron-transfer photochromic behaviors with completely different photoresponsive rate and coloration contrast, which are contributed to the distinct interfacial contacts of electron donors and acceptors. Interestingly, photoluminescence properties of two compounds show different changes during the coloration-decoloration process (the slightly red-shift and weakening of the fluorescence for 1vs. the almost completely quenching of the fluorescence for 2). The present study illustrates the influence of positional isomerism on the resultant supramolecular networks and photochromic behaviors accompanying adjustable photoluminescence properties.

A dual-emitting inorganic-organic hybrid material with emission intensity enchanced via electron-transfer photochromism

A new photochromic inorganic-organic hybrid material [(N-MeIQL)BiCl4] (1, N-MeIQL+ = N-methylisoquinolinium) has been solvothermally synthesized. In 1 the N-MeIQL+ cation is obtained by in situ alkylation of isoquinoline in the acidized methanol solution, and it is firstly reported that N-MeIQL+ acts as an organic template for the design and synthesis of photochromic material. Compound 1 exhibits reversible photochromism between colorless and bright yellow. Moreover, compound 1 displays dual-emitting luminescence and the lifetimes of the two emissions at 410 nm and 640 nm were measured to be 0.71 ns and 0.28 ms, respectively, indicating the fluorescence and phosphorescence characteristics. It is notable that unlike the luminescence quenching of normal photochromic materials in the process of photoinduced coloration, and the emission intensity of 1 can be significantly enhanced via electron-transfer photochromism. The studies of electron-transfer photochromism and photomodulated luminescence provide useful insight into the design of new photoresponsive materials.

The Influence of Anions on Electron-Transfer Photochromism of Bipyridinium-Derived Metal–Organic Materials

As a new class of multifunctional materials, photochromic materials have received much attention due to their potential applications in many fields. In order to investigate the effect of anions on ...

Chromism of three coordination polymers based on 1-(2-carboxyethyl)-4,4′-bipyridinium ligand

Three novel coordination polymers (CPs) based on 1-(2-carboxyethyl)-4,4′-bipyridinium bromide (HCBbpyBr) have been prepared {[Cd2(CBbpy)(m-BDC)2(H2O)4]·H2O}n (1), {[Ni(CBbpy)2(H2O)2](p-BDC)·6H2O}n (2), {[Co(CBbpy)2(H2O)2](p-HBDC)2·3H2O}n (3) (m-H2BDC = 1,3-benzenedicarboxylic acid; p-H2BDC = 1,4-benzenedicarboxylic acid). The crystal structures and chromic behaviors of three compounds have been studied. Single-crystal X-ray analyses reveal that compound 1 features a 2D-layered structure, compounds 2 and 3 have similar 1D double chain-like structure. Compound 1 displays electron-transfer (ET) photochromism, compound 2 exhibits ligand-based ET photochromism and metal-based hydrochromism owing to ligand-field change induced by de-/rehydration, while compound 3 exhibits ET thermochromism accompanying ligand-field change around the metal. The differences in the central metal ions and auxiliary carboxylate units have a great influence on the final structures, and further result in their different chromic behaviors.

A Smart Photochromic Semiconductor: Breaking the Intrinsic Positive Relation Between Conductance and Temperature.

Breaking the intrinsic rule of semiconductors that conductivity increases with increase of temperature and realizing a dramatic dropping of conductivity at high temperature may arouse new intriguing applications, such as circuit overload or over-temperature protecting. This goal has now been achieved through T-type electron-transfer photochromism of one organic semiconductor assembled by intermolecular cation⋅⋅⋅π interactions. Conductivity of the viologen-based model semiconductor (H2 bipy)(Hox)2 (H2 bipy=4,4'-bipyridin-1,1'-dium; ox=oxalate) increased by 2 orders of magnitude after photoinduced electron transfer (a record for photoswitchable organic semiconductors) and generation of radical cation⋅⋅⋅π interactions, and fell by approximately 81 % at 100 °C through reverse electron transfer and degeneration of the radical cation⋅⋅⋅π interactions. The model semiconductor has at least two different electron transfer pathways in the decoloration process.

Multi-responsive host-guest MOFs derived from ethyl viologen cations

The self-assembly reaction of TM2+ (TM = Zn, Cd), 1,3-benzenedicarboxylic acid (m-H2BDC), and ethyl viologen cation (EV2+ = 1,1′-bis(ethyl)-4,4′-bipyridinium dication) leads to two new host-guest MOFs {(EV)0.5[TM1.5(m-BDC)2]}n (1, Zn; 2, Cd), of which TM1.5(m-BDC)2]2- acts as host anion and EV2+ acts as guest cation. The two compounds have different chromic properties. Compound 1 exhibits both electron-transfer (ET) photochromism under indoor light, sunlight and UV light irradiation and ET thermochromism, while compound 2 only exhibits ET photochromism under sunlight and UV light irradiation. Compounds 1 and 2 have the same structure except for different coordination metal ions, the effects of metal ions on the chromic behaviors of two compounds have been explored.

Novel photo- and/or hydrochromic organometallics derived from methyl viologen cations

By the reaction of TM(NO3)2 (TM = Co, Ni, Cd) with 1,1′-bis(methyl)-4,4′-bipyridinium dibromide (MV·2Br) and 1,4-benzenedicarboxylic acid (p-H2BDC), three novel organometallic compounds have been obtained, (MV)[Co(H2O)6](p-BDC)2·4H2O (1), (MV)[Ni(H2O)6](p-BDC)2·4H2O (2), {(MV)[Cd(p-BDC)(Br)2]}n (3). Compounds 1 and 2 are isostructural ionic salts made up of one MV2+ cation, one [TM(H2O)6]2+ cation, two uncoordinated p-BDC2− anions, and four crystallization water molecules, and linked by extensive hydrogen bonds to afford the 3D networks; Compound 3 is constituted by MV2+ cations and zigzag chains of Cd(II) ions bridged by the deprotonated p-BDC2- species through four carboxylate oxygen atoms to form a 1D coordination polymer. Compound 3 exhibits electron-transfer photochromism similar to other viologen-based materials, while 1 and 2 are photoinert. However, the thermal stimulation not only makes compounds 1 and 2 exhibit hydrochromic behaviors by means of dehydration and rehydration of the crystals, but also can induce a phase transition from photochemically inert to active states, demonstrating a positive role in improving photoinduced electron transfer.

Tetrazole-viologen based metal complex: Photochromism and reversible fluorescence modulation

By UV–Vis spectroscopy, ESR study, X-ray photoelectron spectroscopy and theoretical calculation, a newly synthesized tetrazole-viologen based zinc(II) coordination compound, [ZnCl2(3-TzV)(H2O)] (3-TzV=N-(3-tetrazylbenzyl)-4,4′-bipyridinium), was found to exhibit electron-transfer photochromism. In addition to the commonly observed decrease in fluorescence intensity, the fluorescence color changes from green to blue during the coloration, and this change is reversible by altering UV–Vis irradiation and heating for at least seven cycles. The unprecedented photoswitching of fluorescence color for viologen-based photochromic compounds offers a good candidate for multicolor emitting display.

Rare electron-transfer photochromic and thermochromic difunctional compounds

Two new isostructural coordination compounds exhibit the rare properties of both electron-transfer (ET) photochromism and ET thermochromism, which are significantly affected by halogen atoms.

Influence of Supramolecular Interactions on Electron-Transfer Photochromism of the Crystalline Adducts of 4,4′-Bipyridine and Carboxylic Acids

We have studied the electron-transfer photochromism of the crystalline adducts of 4,4′-bipyridine (Bpy) and carboxylic acids and revealed the key structural parameters that decide whether the photochromism can happen for the first time. Experimental and theoretical analyses on nine known examples showed that the hydrogen bonds, instead of π–π stacking interactions, are the defining factor to the photochromism. Only the presence of N–H···O hydrogen bonds can fulfill the electron transfer from the carboxylate group to the Bpy part, although both the N···O separations of O–H···N and N–H···O hydrogen bonds are suitable for the so-called through-space electron transfer. These results can not only help to screen out the photochromic species from the known hundreds of Bpy–carboxylic acid adducts deposited in the Cambridge Crystallographic Data Centre (CCDC) database but also guide the design and syntheses of new adducts using diverse N-heterocyclic aromatic molecules and carboxylic acids.