Ligands play a crucial role in the supramolecular photoluminescence properties of Pt­(II) square-planar complexes. To improve the luminescence color responses of N∧C∧N cyclometalated Pt­(II) complexes to external stimuli such as mechanical stress and chemical vapors, we have conducted a steric engineering of the previous systems 1a–1d [Inorg. Chem. 2017, 56, 4978–4989] by introducing two tert-butyl groups to the tridentate ligand to form complexes 2a–2c. Unlike the “too low” or “too high” steric hindrance of the NCNPt core in 1a–1d, the combined steric effects of the tert-butyl groups at one side and the pentiptycene group at the other side of the NCNPt core in 2b are “just right” for generating as-prepared powders with pure monomer (green) emission or pure excimer (red) emission, depending on the rate of precipitation from solutions. The synergistic steric effects are also beneficial to the solid-state luminescence quantum efficiency (30–36%). As a result of the differences in steric interactions and thus in the relative monomer vs excimer emission intensity, each complex of 2a–2c performs a two-step luminescence mechanochromism and vapochromism with different color patterns. This work provides an intriguing example of steric engineering of Pt­(II) complexes toward highly emissive molecular solids with high-contrast mechanochromic and vapochromic luminescence.

The interplay of mechanical grinding and aniline vapor fuming on the fluorescence of the pentiptycene-anthracene-pentiptycene π-conjugated molecules PAP-Cn, where n is 4, 8, 12, or 16 and refers to the number of carbon atom in the terminal alkyl chains, in solid films are reported. The differences and similarities among the four homologs have led to a conclusion of the formation of an emissive triplex state for the ground and fumed films. Thermogravimetric analysis reveals the guest-host molar ratio and the retention ability of the aniline on the various types of films. A stepwise protocol of fuming-grindingannealing is developed for fluorimetric differential sensing of eight substituted aniline vapors with a single probe of PAP-C8. The role of the bulky pentiptycene groups in the observed fluorescence properties is also discussed.

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