Dual-Phase Multi-Stimuli-Responsive Luminescence from a Pentiptycene-Linked Binuclear Cyclometalated Platinum(II) Complex.

While numerous stimuli-responsive molecular systems have been reported, materials that respond to external stimuli in both solution and solid phases remain rare. Herein, we report a bis(phenylsulfonyl)pentiptycene (BPSP)-linked binuclear N∧C∧N cyclometalated Pt(II) acetylide complex that exhibits dual-phase luminochromic responses (DPLR) to multiple stimuli. These include temperature changes and the presence of Ag(I), Cu(I), dimethyl sulfoxide (DMSO), or O2 in tetrahydrofuran (THF) solution, as well as mechanical grinding and benzene vapor in the solid state. The luminochromic behaviors arise from switching between green monomer and red excimer emission of the NCNPt-acetylide chromophores. In solution, excimer emission dominates due to the folded conformation of the BPSP linker but can be suppressed by external stimuli, resulting in red-to-green switching. In the solid state, the BPSP linker adopts an extended conformation that promotes intermolecular π-π interactions. The initial green monomer emission shifts to red emission upon mechanical grinding (green-to-red switching), and partial recovery of monomer emission, manifested as red-to-orange switching, can be achieved by fuming the ground samples with benzene or ethyl acetate vapors. This work highlights the utility of a conformationally flexible linker for designing binuclear Pt(II) complexes capable of luminochromic behavior across both solution and solid phases.