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photochemical cycloaddition and temperature-dependent breathing in pillared-layer metal–organic frameworks

Science Bulletin 2019年第24期64卷 1881-1889页

作者： Qingqing Pang Binbin Tu Lingyi Yang Qiaowei Li Department of Chemistry Collaborative Innovation Center of Chemistry for Energy Materials (iChEM) and Shanghai Key Laboratory of Molecular Catalysis and InnovativeMaterials Fudan University

Single crystallinity of metal–organic frameworks(MOFs) enables the studies of their flexible behaviors with atomic precision. Here, we investigated the structural transformations triggered by photochemical cycloaddition and with temperature-dependent breathing in a series of pillared-layer MOF structures using a variety of pyrazolecarboxylate linkers for the layers and bipyridyl linkers as the pillars. The ethylenic double bonds from the pillars in close proximity undergo quantitative and seteroselective photochemical [2 + 2] cycloaddition upon UV irradiation, transforming the MOFs into structures with cyclobutane-based pillars. Furthermore, reversible breathing of the new pillared-layer MOF was evidenced by the 10.8% unit cell parameter change along c axis upon temperature change between 298 and 173 K. As revealed by single crystal X-ray diffraction, this transformation originates from the relative flattening of the wavy layers upon cooling. These two different types of characteristic structural transformations responding to inherent reactions and external stimuli happen at single crystalline state, providing a well-defined robust system with controlled flexibility.

关键词： Pillared-layer MOF photochemical cycloaddition Structural transformation Breathing MOF Reticular chemistry

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Phase-mediated controllable intramolecular and intermolecular photocycloadditions assisted by supramolecular templates

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Science China Chemistry 2022年第6期65卷 1129-1133页

作者： Yi-Shou Wang Li-Ying Sun Yao-Yu Wang Ying-Feng Han Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education Xi’an Key Laboratory of Functional Supramolecular Structure and MaterialsCollege of Chemistry and Materials ScienceNorthwest UniversityXi’an710127China

Understanding and controlling supramolecular template effect assembly via a photochemical reaction in different solid and solution phases is one of the main topics in photochemistry. Here, an interesting case of phase-mediated controllable intramolecular/intermolecular photochemical [2+2] cycloadditions assisted by supramolecular templates was demonstrated. Direct irradiation of the complexes in solution yields intramolecular photoproducts exclusively, whereas exposure of the solid powder sample under the same conditions yields intermolecular dinuclear species quantitatively. The nature of the phase and supramolecular interaction affects the geometrical arrangements of the metallacycles, leading to different cycloaddition products under photoirradiation. The crystal structures of different products were investigated by single-crystal X-ray diffraction, nuclear magnetic resonance(NMR) spectrometry, and electrospray ionization mass spectrometry(ESI-MS).

关键词： N-heterocyclic carbene photochemical cycloaddition template synthesis topochemistry stacking interactions

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