Jye-Shane Yang

Mechanically responsive molecular crystals offer a powerful platform for transducing molecular motion into macroscopic mechanical work, yet molecular‐level understanding of how crystal structures govern molecular motion and, consequently, mechanical behavior remains limited. A notable example is the anthracene‐pentiptycene‐semifluorinated alkyl crystal 1‐F4 , recently reported to exhibit large elastic bending (ε ≈ 12%) and >15% photoinduced crystal expansion without fracture. Here, we investigate a homologous crystal series ( 1‐F n , n = 2, 3, 4, and 6) and reveal a mechanically coupled supramolecular scissoring motion that governs their diverse mechanical responses. The balance between scissor stretchability and compressibility, tuned by semifluorinated alkyl substituents, dictates the deformation mode, elasticity, and crystal integrity. An optimally balanced scissor state in 1‐F4 enables exceptional elastic and photomechanical deformation while preserving crystal integrity, whereas fully‐extended ( 1‐F2 ), over‐contracted ( 1‐F6 ), or mechanically unbalanced ( 1‐F3 ) scissor states lead to brittle failure or explosive photosalient behavior. These results establish a direct structure−motion−property relationship within this homologous series, demonstrating that key mechanical properties, including deformation mode and elastic limit, are encoded in the initial scissor geometry within the crystal packing arrangement.

Mechanically responsive molecular crystals offer a powerful platform for transducing molecular motion into macroscopic mechanical work, yet molecular‐level understanding of how crystal structures govern molecular motion and, consequently, mechanical behavior remains limited. A notable example is the anthracene‐pentiptycene‐semifluorinated alkyl crystal 1‐F4 , recently reported to exhibit large elastic bending (ε ≈ 12%) and >15% photoinduced crystal expansion without fracture. Here, we investigate a homologous crystal series ( 1‐F n , n = 2, 3, 4, and 6) and reveal a mechanically coupled supramolecular scissoring motion that governs their diverse mechanical responses. The balance between scissor stretchability and compressibility, tuned by semifluorinated alkyl substituents, dictates the deformation mode, elasticity, and crystal integrity. An optimally balanced scissor state in 1‐F4 enables exceptional elastic and photomechanical deformation while preserving crystal integrity, whereas fully‐extended ( 1‐F2 ), over‐contracted ( 1‐F6 ), or mechanically unbalanced ( 1‐F3 ) scissor states lead to brittle failure or explosive photosalient behavior. These results establish a direct structure−motion−property relationship within this homologous series, demonstrating that key mechanical properties, including deformation mode and elastic limit, are encoded in the initial scissor geometry within the crystal packing arrangement.

Achieving fluorescence activation of green fluorescence protein (GFP) chromophores in solution under ambient conditions has been a long‐standing challenge in organic photochemistry. In this context, the meta‐ amino substituent effect, originally recognized for promoting fluorescence in stilbenes, has been identified as a powerful design principle for enhancing emissive properties of GFP chromophores. Beyond fluorescence turn‐on, m‐ amino‐substituted GFP chromophores exhibit distinctive photophysical characteristics, including pronounced solvatofluorochromism and atypical excited‐state deactivation pathways in both protic and polar aprotic solvents. These unique features have enabled their development as environmentally sensitive fluorescent probes and wash‐free cell‐imaging dyes. This review concisely summarizes key advances in this area over the past 2 decades.

A light‐powered atroposelective ratcheting system based on a desymmetrized pentiptycene scaffold is reported. This structural framework enforces templated donor–acceptor (D–A) arrangements capable of distinguishing between rapidly equilibrating atropisomers, enabling atroposelective Z → E photoisomerization that selectively suppresses the consumption of one atropisomer and leads to its accumulation under continuous irradiation. Ultrafast transient spectroscopic studies and theoretical calculations reveal that this photochemical atroposelectivity arises from electronic interactions between the donor and acceptor moieties in the excited state. Such an atroposelective ratchet could potentially be harnessed to construct light‐driven rotary molecular motors (LRMMs). These results highlight the role of conformer‐dependent photochemistry in achieving precise photochemical control over molecular motion.

Guest‐release induced responsive behaviors in nonporous organic solvate crystals remain elusive due to the lack of well‐defined diffusion pathways and the rarity of crystal‐to‐crystal transitions. Here, we report a pentiptycene‐derived nonporous organic solvate ( 1B ) that exhibits a striking blue → green → yellow thermochromic fluorescence sequence through a two‐stage crystal‐to‐crystal transformation. In the first stage, subtle gear‐like rotations transiently open a zigzag diffusion pathway, releasing dichloromethane (DCM) and generating a green‐emissive phase ( 1G ). In silicone oil, asymmetric bubble evolution during DCM release drives directional crystal propulsion. A second heating step triggers a ∼90° correlated gear rotation that reconfigures alkyl conformation and anthracene packing, producing excimer‐based yellow emission ( 1Y ). These coupled sequential optical, mechanical, and structural responses reveal a unique paradigm of guest‐driven dynamics in nonporous solvate crystals.

Guest‐release induced responsive behaviors in nonporous organic solvate crystals remain elusive due to the lack of well‐defined diffusion pathways and the rarity of crystal‐to‐crystal transitions. Here, we report a pentiptycene‐derived nonporous organic solvate ( 1B ) that exhibits a striking blue → green → yellow thermochromic fluorescence sequence through a two‐stage crystal‐to‐crystal transformation. In the first stage, subtle gear‐like rotations transiently open a zigzag diffusion pathway, releasing dichloromethane (DCM) and generating a green‐emissive phase ( 1G ). In silicone oil, asymmetric bubble evolution during DCM release drives directional crystal propulsion. A second heating step triggers a ∼90° correlated gear rotation that reconfigures alkyl conformation and anthracene packing, producing excimer‐based yellow emission ( 1Y ). These coupled sequential optical, mechanical, and structural responses reveal a unique paradigm of guest‐driven dynamics in nonporous solvate crystals.

We report two stimuli-responsive luminescent assemblies based on homoleptic alkynyl gold(I) clusters, [(AuC≡CR)ₙ], where R is a pentiptycene unit and n = 4 or 6. The green-emissive form (1Gs) adopts a vortex-like arrangement and exhibits photochromic luminescence, shifting from green to yellow to orange. In contrast, the yellow-emissive form (1Ys) adopts a less rigid structure, likely a radial arrangement, and displays thermochromic luminescence, transitioning from yellow to orange to red. These divergent behaviors arise from structural differences in η²-Au bonding, which modulate supramolecular geometry, pentiptycene-pentiptycene packing, and the strength of Au···Au interactions, thereby governing excited state aurophilicity. This work demonstrates the first luminochromic [(AuC≡CR)ₙ] system and introduces a design strategy that leverages pentiptycene scaffolds to regulate excited-state aurophilicity for photo- and thermoresponsive luminescence.

The fluorescence of nitroaromatic fluorophores is highly sensitive to their environment and often exhibits a narrow “fluorescent window” in both solution and solid states. This limitation arises from the various fluorescence‐quenching pathways, including S₁ → T_n intersystem crossing (ISC), formation of a twisted intramolecular charge transfer (TICT) state, and antiparallel molecular stacking. Here, we report a series of nitro‐substituted triphenylamines (nitro‐TPAs), in particular the pentiptycene‐derived nitro‐TPAs PX series, to investigate whether combined steric and electronic engineering can broaden the fluorescent window across a wide polarity range and in the solid state. While substituent electronic effects tune the push‐pull character, the bulky pentiptycene scaffold shields the nitrogen center from solvation and suppresses intermolecular stacking in the solid phase. Notably, the isocyanide derivative PNC exhibits fluorescence in all six tested solvents, n‐hexane, toluene, dichloromethane, N,N‐dimethylformamide, and acetonitrile, as well as in both crystalline and powdered forms. This work demonstrates the effectiveness of integrating steric and electronic strategies to expand the fluorescence window of flexible nitroaromatic systems.

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.