The multicolour fluorescence responses to external mechanical forces vs. internal photomechanical stresses of a molecular solid are demonstrated and compared.

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.

We report herein a porous supramolecular framework formed by a linear mononuclear Au(I) complex (1) via the tongue-and-groove-like joinery between the pentiptycene U-cavities (grooves) and the rod-shaped π-conjugated backbone and alkyl chains (tongues) with the assistance of C−H•••π and aurophilic interactions. The framework contains distorted tetrahedral Au 4 units, which undergo stepwise and persistent photoinduced Au(I)− Au(I) bond shortening (excited-state aurophilicity), leading to multicolored luminescence photochromism. The one-dimensional pore channels could accommodate different solvates and guests, and the guest inclusion-induced luminescence enhancement (up to 300%) and/or vapochromism are characterized. A correlation between the aurophilic bonding and the luminescence activity is uncovered by TDDFT calculations. Isostructural derivatives 2 and 3 corroborate both the robustness of the porous supramolecular assembly and the mechanisms of the stimulation-induced luminescence properties of 1. This work demonstrates the cooperation of aurophilicity and structural porosity and adaptability in achieving novel supramolecular photochemical properties.

The electrochemical stability of polyaniline (PANI) films is a key issue for their application as electrode materials. This work demonstrates that a low fraction (<5%) of pentiptycene incorporation of the PANI conjugated backbone could significantly enhance the capacitive performance and charge-discharge cycling stability of PANI films, attributable to the clipping effect of pentiptycene cavities that restricts motional freedom of polymer chains and promotes interchain conductivity.