A square-planar platinum(II) complex, Pt(DiBrbpy)(C≡CC6H4Et-4)2 (1) (DiBrbpy = 4,4-dibromo-2,2′-bipyridine), and crystals of its three solvated forms, namely, 1·DMSO, 1·1/2(CH3CN), and 1·1/8(CH2Cl2), were developed and characterized. 1·DMSO and 1·1/2(CH3CN) contain quasi-dimeric and dimeric structures with luminescence in the visible range, whereas 1·1/8(CH2Cl2) exhibits NIR luminescence at 1022 nm due to its intrinsic 1-D “platinum wire” stacking structure with strong Pt–Pt interactions. 1·1/8(CH2Cl2) 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 CH3CN 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(CH3CN), and 1·1/8(CH2Cl2), 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 3MLCT/3LLCT and 3MMLCT in solid-state as supported by time-dependent density functional theory (TD-DFT) calculations.

A square-planar bis(σ-acetylide) Pt(II) complex containing dual-recognition sites was designed, synthesized and used as a colorimetric/luminescent sensor for detecting the vapor of benzene compounds.

The square-planar diimine-platinum(II) complex, Pt(4-Brbpy)(CCC6H5)2 (1) (4-Brbpy = 4-bromo-2,2′-bipyridine), was prepared and characterized. Solid-state 1 exhibits reversible thermo- and mechanical-grinding-triggered color and luminescence changes. When crystalline 1·2(CH2Cl2) or 1·2(CHCl3) are heated or ground, the original bright yellow-green emission centered at 525 (549, sh) nm changed to 637 and 690 nm, corresponding to thermo- and mechanochromic response shifts of approximately 88–112 nm and 141–165 nm, respectively. Meanwhile the crystalline state changes into an amorphous phase in both processes. Once the amorphous sample absorbs organic vapors, it can be reverted to the original crystalline state, along with red luminescence turning back to yellow-green emission. The reversibility of thermo- and mechanical-grinding-triggered chromic luminescence properties has been dynamically monitored by emission spectra and X-ray diffraction patterns. The dramatic thermo- and mechanical-grinding-triggered emission red shifts are most likely due to the conversion of the 3MLCT/3LLCT emission state into the 3MMLCT triplet state.

The square-planar diimine-platinum(II) complex, Pt(4-Brbpy)(CCC6H5)2 (1) (4-Brbpy = 4-bromo-2,2′-bipyridine), was prepared and characterized. Solid-state 1 exhibits reversible thermo- and mechanical-grinding-triggered color and luminescence changes. When crystalline 1·2(CH2Cl2) or 1·2(CHCl3) are heated or ground, the original bright yellow-green emission centered at 525 (549, sh) nm changed to 637 and 690 nm, corresponding to thermo- and mechanochromic response shifts of approximately 88–112 nm and 141–165 nm, respectively. Meanwhile the crystalline state changes into an amorphous phase in both processes. Once the amorphous sample absorbs organic vapors, it can be reverted to the original crystalline state, along with red luminescence turning back to yellow-green emission. The reversibility of thermo- and mechanical-grinding-triggered chromic luminescence properties has been dynamically monitored by emission spectra and X-ray diffraction patterns. The dramatic thermo- and mechanical-grinding-triggered emission red shifts are most likely due to the conversion of the 3MLCT/3LLCT emission state into the 3MMLCT triplet state.