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Photochromic materials coupled with photoswitchable luminescence functionalities are of particular interest due to their potential applications in switches and optical memory devices. However, the construction of such materials, especially those with two-color emission states, is still challenging. In this context, a rare Zn7 cluster-based host–guest MOF material, (bbmp)[Zn7(IPA)6(OH)4(H2O)2] (1) (H2IPA = isophthalic acid, bbmp·2I = 4,4′-([1,1′-biphenyl]-4,4′-diyl)bis(1-methylpyridin-1-ium) diiodide), was prepared by encapsulating an organic cation into an anionic MOF produced from zinc cations and isophthalic acid ligands, which exhibits reversible naked detectable photochromic properties varying from yellow to green upon UV-Vis light irradiation. The photoactive guest bbmp2+ and the short O⋯N+ distances between the oxygen atoms of the carboxylate groups and the pyridine ring play a crucial role in the photochromism of this compound. More interestingly, the luminescence color of this cluster-based host–guest material can be reversibly switched from green to blue upon irradiation, exhibiting photoswitchable luminescence properties. [ABSTRACT FROM AUTHOR]

Mechanoresponsive luminescent materials refer to materials exhibiting luminescence intensity and/or color change in the solid-state induced by external mechanical stimulation and are attracting considerable attention for their potential applications in many fields. For organic molecular materials, the mechanoresponsive luminescence phenomenon can significantly depend on the molecular packing modes and orientations of individual fluorophores, enabling the development of molecular materials with mechanoresponsive luminescence characteristics. Naphthalene diimides (NDIs) are well-known organic dyes with an electron-deficient plane, making them excellent candidates for exploring mechanoresponsive luminescence properties owing to their photophysical and photochemical properties that depend on the packing modes and are very sensitive to the micro-environment. In this work, a new binary charge transfer cocrystal complex with sensitive mechanoresponsive luminescence, IsoNDI·anisole (C1) (IsoNDI = N,N-di(4-pyridylacylamino)-1,4,5,8-naphthalene diimide), was designed and prepared. C1 shows interesting enhanced emission characteristics and reversible mechanochromic luminescence properties with a prominent color change from orange to bright green-yellow by mechanical grinding. This study demonstrates that the development of new mechanoresponsive luminescent materials through donor–acceptor interactions is an effective avenue. [ABSTRACT FROM AUTHOR]