A square-planar platinum(II) complex, Pt(DiBrbpy)(C≡CCHEt-4) (1) (DiBrbpy = 4,4-dibromo-2,2'-bipyridine), and crystals of its three solvated forms, namely, 1·DMSO, 1·1/2(CHCN), and 1·1/8(CHCl), were developed and characterized. 1·DMSO and 1·1/2(CHCN) contain quasi-dimeric and dimeric structures with luminescence in the visible range, whereas 1·1/8(CHCl) exhibits NIR luminescence at 1022 nm due to its intrinsic 1-D "platinum wire" stacking structure with strong Pt-Pt interactions. 1·1/8(CHCl) represents the first compound based on platinum(II) diimine bis(σ-acetylide) molecular units with the NIR luminescence beyond 1000 nm. 1 selectively responds to DMSO and CHCN by changing its color and luminescence property and the three solvated forms can be reversibly converted to each other upon exposure to corresponding solvent vapors. Their desolvated forms, namely 1a, 1b, and 1c, obtained after heating 1·DMSO, 1·1/2(CHCN), and 1·1/8(CHCl), respectively, can also be restored to the original solvated forms upon exposure to corresponding solvent vapors. 1a and 1b emit NIR luminescence peaked at 998 and 1018 nm respectively, suggesting indirect synthetic methods as powerful alternatives to achieve NIR luminescence with long wavelength. In contrast, 1c exhibits a red luminescence with a broad unstructured emission band centered at 667 nm. All the responses to organic solvent vapors and heating are due to the structural transformations which result in the conversion of the lowest energy excited states between MLCT/LLCT and MMLCT in solid-state as supported by time-dependent density functional theory (TD-DFT) calculations.

Luminescence switching materials are vital to various data security-related techniques, including data encryption–decryption. Here, we report a family of pseudopolymorphs based on a diimine–platinum­(II) complex, Pt­(Me3SiCCbpyCCSiMe3)­(CCC6H4Br-3)2 (1), and systematically studied the influence of stacking modes on luminescence switching behaviors. Upon exposure to heat or tetrahydrofuran vapor, these pseudopolymorphs exhibit unusual stacking mode-intervened luminescence switching (SMILS) property that non-columnar and quasi-columnar pseudopolymorphs undergo single- and multi-step conversion processes, respectively, to the same non-columnar products. Systematic studies revealed that the unique SMILS behavior is caused by the existence of stable intermediate products as well as different conversion processes of pseudopolymorphs with distinct stacking modes. Such a new property leads to the self-encryption function of 1, which is very important for improving the existing data encryption–decryption technique. On this basis, we developed a facile, reusable, equipment-free technique with 1 as the only starting material and realized data encryption–decryption successfully.

A concurrent, selective, naked-eye perceivable, sensitive, reversible, reproducible, and easy to use sensor for detecting vapors of benzene compounds has been developed.

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Although many strategies have been used to help design effective near-infrared (NIR) luminescent materials, it is still a huge challenge to realize long-wavelength NIR luminescence of diimineplatinum(II) complexes in the solid state. Herein, we have successfully achieved long-wavelength NIR luminescence of a family of diimineplatinum(II) complexes based on a new strategy that combines a one-dimensional (1D) "Pt wire" structure with the electronic effect of the substituent. The structures of six solvated diimineplatinum(II) complexes based on 4,4-dichloro-2,2′-bipyridine or 4,4-dibromo-2,2′-bipyridine and 4-substituted phenylacetylene ligands have been determined, namely, and 6• 1 / 4 toluene. All of them crystallize in the monoclinic space group C2/c or C2/ m and stack in the 1D "Pt wire" structure. In the solid state, six complexes exhibited unusual long-wavelength metal−metal-to-ligand charge-transfer luminescence that peaked at 984, 1044, 972, 990, 1022, and 935 nm, respectively. Interestingly, 2• 1 / 2 THF has the shortest Pt•••Pt distance and the longest emission wavelength among the six complexes. As far as we know, the luminescence of 2• 1 / 2 THF at 1044 nm is the longest emission wavelength among known diimineplatinum(II) complexes. Systematic studies revealed that good molecular planarity, suitable substituent position, weak hydrogen-bond-forming ability of the substituents, appropriate molecular bending, and weakening of the interaction between solvated molecules and platinum molecules are conducive to the construction of a 1D "Pt wire" structure of the diimineplatinum(II) complex. Furthermore, the emission energy of the complex is mainly determined by the strength of the Pt−Pt interaction and electronic effect of the substituent.