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A viologen-based Borromean entangled porous framework was found to be sensitive to both Cu and Mo X-ray sources, showing rapid photochromic response and recovery within one minute. The X-ray-induced photochromic process is accompanied by a reversible single-crystal-to-single-crystal (SC-SC) structural transformation, an unprecedented phenomenon for X-ray sensitive materials. The complex can be further processed into portable thin films for detecting the dose of the X-ray exposure. Moreover, the photochromism can occur over a broad temperature range of 100-333 K, both in the form of single crystals and thin films, making it a potential candidate for practical indoor and outdoor applications.

A flexible bipyridinium ligand with Lewis acidic sites has been introduced into two isomorphous metal-organic frameworks to yield luminescent porous materials with subtriangular pore windows, which exhibit sensitive fluorescent response for ammonia molecules and can be proved at the molecular level by Raman spectroscopy.

The past ten years have evidenced the rapid development of bipyridinium-based coordination polymers, however, the design and synthesis of photo-switchable luminescent materials with a non-destructive readout capability based on bipyridinium ligands are still at the primary stage. In this work, two new coordination polymers with a bipyridinium-functionalized m-benzenedicarboxyl ligand were synthesized for this purpose. By using anions with different geometries, the molecular linkage and packing structure have been adjusted, and thus allow the two title compounds to exhibit eye-detectable color development with different photoresponsive rates, and distinct luminescence behaviors. Furthermore, compound 2 is the first reported Zn-based luminescent coordination polymer with a non-destructive readout capability. These results can not only help to further understand the structure-photosensitivity relationships of bipyridinium-based systems but also guide the design and synthesis of more luminescent materials with a non-destructive readout capability.

Although naphthalene diimide (NDI) and its derivatives have been widely used for organic Li-ion batteries (OLIBs), they are limited by a low lithium uptake capacity and ambiguous lithiation mechanism. Herein, we report two isometric thionated-NDI cathodes (cis-2S and trans-2S) obtained by replacing O with S in the imide groups which improves the battery performance compared with parent NDI (P-NDI). Remarkably, the position of S atoms plays an important role as the potential plateau of cis-2S was 100 mV higher than trans-2S, 256 mV higher than P-NDI, and the capacity of cis-2S was twice than that of trans-2S, four times as P-NDI after 400 cycles. The in situ Raman, X-ray photoelectron spectroscopy (XPS), and DFT calculations revealed that the lithiation process occurs on the less electronegative S atoms. For cis-2S, the electron density on the lithiation sites is lower than trans-2S because of a stronger electron inductive effect. This in turn enhances the redox potential and cycling stability of cis-2S. This contribution provides an additional molecular engineering strategy to develop novel organic cathode materials for high performance OLIBs.

Interests in chromic materials are rapidly increasing for their potential applications as smart responsive materials. However, the majority of the existing ones are triggered by merely one or two outer stimuli and the few multi-stimuli responsive examples still suffer from their confining functioning state such as solution or polymer. To address these challenges, a new generation of multi-stimuli responsive chromic materials is being intensively pursued. In this article, we report a neoteric supramolecular solid material by assembling Co­(II) ion with bipyridinium-functionalized ligand in solvothermal condition. This material can perform reversible chromic behaviors in response to 365 nm light, heat, vacuum, ammonia, ethanediamine, and some organic solvents. Meanwhile, it exhibits excellent structural stability and reversibility to cope with these stimuli.

A multiple responsive organic small molecular material has been developed, which exhibits dual pathway photoreactions and gives turn-on luminescence and photocoloration under different light sources.