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Construction of heterojunctions to photocatalysts is one of the most promising approaches to improve charge separation efficiency; however, the established constructing processes usually require high‐temperature conditions and/or the adding of highly concentrated or expensive exotic species, and the improvement of effective contact and charge exchange between heterojunction components remains a problem. This work proposes an unprecedented "photobreeding" method and realizes the direct growth of Zn nanowires and Mott–Schottky heterojunctions from ZnS or viologen‐coated ZnS microspheres through a photochemical reaction at room temperature without external species, while demonstrating the hypothesis proposed 140 years ago on the formation of Zn in the photochromic process of ZnS. After photobreeding of the heterojunctions, the hydrogen production efficiency of the photocatalysts increases by 2 orders of magnitude. This inexpensive, facile and efficient synthetic method will find applications in H2 production, organic synthesis, CO2 reduction, nitrogen fixation, and so on. [ABSTRACT FROM AUTHOR]

Introduction of photochromic properties into semiconductors confers semiconductors with smart behaviors, color‐related applications, and new modulation approaches. Photochromophores with electron‐transfer (redox) behavior, such as viologen and naphthalene diimide, are ideal functional motifs to design photochromic semiconductors owing to good adaptability to the solid matrix, but their reverse reactions are exclusively realized by the thermal mode, which is slow (in dozens of seconds or longer) and thus significantly hinders real applications in the fields that require high‐speed switching. This study reveals that photoexcitation in the electronic absorption band of the π‐aggregate of viologen cation radicals can successfully trigger reverse electron transfer quickly (in 1 s with a continuous‐wave 808 nm laser at a power density of 5 W cm−2; the photothermal effect is excluded), and the first single‐component all‐optically photochromic semiconductor is accordingly discovered. This discovery breaks through a traditional concept that reverse reactions of viologen compounds can not be triggered by the light, and provides a potential approach to realize all‐optical switch of single‐component photochromic smart semiconductors based on electron‐transfer photochromic functional motifs. [ABSTRACT FROM AUTHOR]

2,4,6‐Tri(4‐pyridyl)‐1,3,5‐triazine (tpt) is a widely used ligand for functional coordination compounds. In this work, tpt has shown unprecedented photochromism in the crystalline state. Experimental and theoretical data has revealed that the photocoloration of tpt very likely originates from intramolecular charge separation and the formation of a triplet diradical product. This finding demonstrates a new simple, neutral photochromic molecule and endows the tpt molecule and related compounds with potential optical applications. [ABSTRACT FROM AUTHOR]

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 (H2bipy)(Hox)2 (H2bipy=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. [ABSTRACT FROM AUTHOR]

N, N′-Disubstituted bipyridinium (viologen) and N-monosubstituted bipyridinium compounds are well known for their electron-transfer (ET) photochromic behavior. Their modification has exclusively focused on the N-substituents to date. For the first time, we have studied the photochromic behavior when one pyridyl ring of the bipyridinium is substituted with a multifunctional azole group, and have found that two new coordination compounds based on N-methyl-4-pyridinium tetrazolate (mptz) zwitterion, [Zn(mptz)2Br2] ( 1) and [Cd3(mptz)2Cl6] n⋅4 n H2O ( 2), exhibit typical ET photochromic behavior owing to photoinduced ET from halogen anion to the mptz ligand. This work demonstrates a new simple, neutral photoactive molecule with electron-accepting ability, which may act as a photoactive component for materials with potential photoswitching and photocatalysis applications. [ABSTRACT FROM AUTHOR]

Electron-transfer (redox) thermochromism was successfully used for switching the conductance of semiconductors, by introducing a thermally active organic component into an inorganic semiconducting framework. A moisture-resistant semiconductor {(MV)2[Pb7Br18]} n (MV2+=methyl viologen cation) has been prepared through an in situ synthetic method for MV2+. It features a rare 3D haloplumbate open framework and unprecedented electron-transfer thermochromic behavior in haloplumbates. The electrical conductivity of this compound dropped significantly after coloration and restored after decoloration, which was satisfactorily explained by valence band XPS and theoretical data. This work not only offers a new approach to modify electrical properties of semiconductors without altering components or structures, but may lead to the development of over-temperature color indicators, circuit overload protectors or photovoltaic materials. [ABSTRACT FROM AUTHOR]

The first bulk electron-transfer photochromic compound with intrinsic second-order nonlinear optical (NLO) photoswitching properties has been synthesized. This system employs an electron-transfer photoactive asymmetric viologen ligand coordinated to a zinc(II) center. [ABSTRACT FROM AUTHOR]

Abstract Materials that may show photochromism under X-rays have higher spatial resolution for visual low-energy X-rays detection over the commercial instruments and greater X-ray sensitivity than silver salt-based radiographic films. In this work, we discovered that the known MOF, [Zn(OOCH) 2 (Bpy)] n (Bpy = 4,4′-bipyridine), showed rare photochromic behaviour upon irradiation of hard and soft X-rays at room temperature. Graphical abstract Rare X-ray-induced photochromism at room temperature, with potential application for X-ray detection, was observed for a known MOF. Image 1 Highlights • Rare X-ray-induced photochromism at room temperature was observed for a known MOF built by non-photochromic ligands. • The mechanism of the X-ray-induced photochromic has been studied. • The MOF shows a potential application on X-ray detection. [ABSTRACT FROM AUTHOR]

Wehave studied the electron-transfer photochromism of the crystallineadducts of 4,4′-bipyridine (Bpy) and carboxylic acids and revealedthe key structural parameters that decide whether the photochromismcan happen for the first time. Experimental and theoretical analyseson nine known examples showed that the hydrogen bonds, instead ofπ–π stacking interactions, are the defining factorto the photochromism. Only the presence of N–H···Ohydrogen bonds can fulfill the electron transfer from the carboxylategroup to the Bpy part, although both the N···O separationsof O–H···N and N–H···Ohydrogen bonds are suitable for the so-called through-space electrontransfer. These results can not only help to screen out the photochromicspecies from the known hundreds of Bpy–carboxylic acid adductsdeposited in the Cambridge Crystallographic Data Centre (CCDC) databasebut also guide the design and syntheses of new adducts using diverse N-heterocyclic aromatic molecules and carboxylic acids. [ABSTRACT FROM AUTHOR]