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Molecular crystals with the ability to transform light energy into macroscopic mechanical motions are a promising class of materials with potential applications in actuating and photonic devices. In regard to such materials, coordination polymers that exhibit dynamic photomechanical motion, associated with a phase transition, are unknown. Herein, we report an intriguing photoactive, one‐dimensional ZnII coordination polymer, 1, derived from 1,3,5‐tri‐4‐pyridyl‐1,2‐ethenylbenzene and 3,5‐difluorobenzoate. Single crystals of 1 under UV light irradiation exhibit rapid shrinking and bending, violent bursting‐jumping, splitting, and cracking behavior. Single‐crystal X‐ray diffraction analysis and 1H NMR spectroscopy reveal an unusual photoinduced phase transition involving a single‐crystal‐to‐single‐crystal [2+2] cycloaddition reaction that results in photomechanical responses. Interestingly, crystals of 1, which are triclinic with space group P1‾ ${P\bar{1}}$ , are transformed into a higher symmetry, monoclinic cell with space group C2/c. This process represents a rare example of symmetry enhancement upon photoirradiation. The photomechanical activity is likely due to the sudden release of stress associated with strained molecular geometries and significant solid‐state molecular movement arising from cleavage and formation of chemical bonds. A composite membrane fabricated from 1 and polyvinyl alcohol (PVA) also displays interesting photomechanical behavior under UV light illumination, indicating the material's potential as a photoactuator. [ABSTRACT FROM AUTHOR]

Due to its high reactivity and oxidative strength, singlet oxygen (1O2) is used in a variety of fields including organic synthesis, biomedicine, photodynamic therapy and materials science. Despite its importance, the controlled trapping and release of 1O2 is extremely challenging. Herein, we describe a one‐dimensional coordination polymer, CP1, which upon irradiation with visible light, transforms 3O2 (triplet oxygen) to 1O2. CP1 consists of CdII centers bridged by 9,10‐bis((E)‐2‐(pyridin‐4‐yl)vinyl)anthracene ligands which undergo a [4+2] cycloaddition reaction with 1O2, resulting in the generation of CP1−1O2. Using microwave irradiation, CP1−1O2 displays efficient release of 1O2, over a period of 30 s. In addition, CP1 exhibits enhanced fluorescence and has an oxygen detection limit of 97.4 ppm. Theoretical calculations reveal that the fluorescence behaviour is dominated by unique through‐space conjugation. In addition to describing a highly efficient approach for the trapping and controlled release of 1O2, using coordination polymers, this work also provides encouragement for the development of efficient fluorescent oxygen sensors. [ABSTRACT FROM AUTHOR]

We report a unique vinyl coordination polymer (CP), [Zn(4‐Fb)2(tkpvb)]n (1, 4‐HFb=4‐fluorobenzoic acid, tkpvb=1,2,4,5‐tetrakis(4‐pyridylvinyl)benzene) that undergoes a rare photopolymerization reaction to form a two‐dimensional CP integrated with a one‐dimensional linear organic polymer. Upon light irradiation at different wavelengths, 1 exhibits an unprecedented phenomenon of photoinduced nonlinear lattice expansion. 1 can be uniformly dispersed in polyvinyl alcohol (PVA) to form the composite film of 1‐PVA. When this film is exposed to UV light, internal minute stresses within crystallites are released by lattice expansion, resulting in a variety of photopolymerization‐driven macroscopic mechanical motions. The findings provide new insights into the conversion of small lattice expansions of CPs into macroscopic mechanical motions based on photopolymerization reactions, which can promote the development of CPs‐based smart photoactuators in the burgeoning field of microrobotics. [ABSTRACT FROM AUTHOR]