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Constructing organic materials with rigid‐planar molecules provides a unique platform for obtaining efficient photoluminescence (PL) by suppressing vibrational relaxation and extending the π‐conjugation. However, the presence of H‐aggregates/excimers resulting from interactions between π electrons and lone pairs during crystalization leads to aggregation‐caused quenching. Here, an alternative pressure‐treatment approach is presented for regulating molecular assembly to brighten rigid‐planar phthalic anhydride (PA) crystals with initial non‐emission. The pressure‐treated PA crystals exhibit significant blue‐light emission under ambient conditions, accompanied by a PL quantum yield of up to 15.7% and Commission International de I'Eclairage color coordinates of (0.20, 0.19). Detailed experiments and calculations reveal that pressure‐treated hydrogen bonds promote the planar rotation among PA molecules, which facilitates intermolecular π‐conjugation. This extended π‐conjugation alters the exciton relaxation channel, thereby triggering blue‐light emission based on charge transfer (CT) states. Remarkably, the obtained PA crystals also exhibit linear piezochromism (4.56 nm GPa−1) as a result of the structural sensitivity of the CT process. This work demonstrates the feasibility of regulating molecular assembly to achieve solid‐state emission in rigid‐planar molecules with initial non‐emission and opens up a new platform toward stimuli‐responsive crystalline materials. [ABSTRACT FROM AUTHOR]

There exist some perovskites materials with no photoluminescence (PL), which will greatly limit the practical applications in photodetection, display and lighting. Here, we achieve an exotic pressure-induced emission (PIE) at a mild pressure of 0.8 GPa from initially non-emissive 2D all-inorganic perovskite Cs3Sb2Br9 quantum dots, when the sample was subjected to external pressure. With the increase of pressure, the PL intensity gradually increases and the emission color transforms from red to green. Combined with subsequent experiments and computations, thus PIE behavior and piezochromism result from the SbBr6 octahedral distortion, accompanied by a structural phase transition from trigonal to monoclinic under pressure. Our work provides a robust strategy to boost the emission efficiency and to construct multi-functional PIE materials with piezochromism in environmentally friendly perovskites, thus facilitating the diverse applications in futural practices.

Piezochromic materials refer to a class of matters that alter their photoluminescence (PL) colors in response to the external stimuli, which exhibit promising smart applications in anti‐counterfeiting, optoelectronic memory and pressure‐sensing. However, so far, most reported piezochromic materials have been confined to organic materials or hybrid materials containing organic moieties with limited piezochromic range of less than 100 nm in visible region. Here, we achieved an intriguing piezochromism in all‐inorganic zero‐dimensional (0D) Cs3Cu2Cl5 nanocrystals (NCs) with a considerable piezochromic range of 232 nm because of their unique inorganic rigid structure. The PL energy shifted from the lowest‐energy red fluorescence (1.85 eV) to the highest‐energy blue fluorescence (2.83 eV), covering almost the entire visible wavelength range. Pressure‐modulated self‐trapped exciton emission between different energy levels of self‐trapped states within Cs3Cu2Cl5 NCs was the main reason for this piezochromism property. Note that the quenched emission, which is over five times more intense than that in the initial state, is retained under ambient conditions upon decompression. This work provides a promising pressure indicating material, particularly used in pressure stability monitoring for equipment working at extreme environments. [ABSTRACT FROM AUTHOR]

There exist some perovskites materials with no photoluminescence (PL), which will greatly limit the practical applications in photodetection, display and lighting. Here, we achieve an exotic pressure-induced emission (PIE) at a mild pressure of 0.8 GPa from initially non-emissive 2D all-inorganic perovskite Cs3Sb2Br9 quantum dots, when the sample was subjected to external pressure. With the increase of pressure, the PL intensity gradually increases and the emission color transforms from red to green. Combined with subsequent experiments and computations, thus PIE behavior and piezochromism result from the SbBr6 octahedral distortion, accompanied by a structural phase transition from trigonal to monoclinic under pressure. Our work provides a robust strategy to boost the emission efficiency and to construct multi-functional PIE materials with piezochromism in environmentally friendly perovskites, thus facilitating the diverse applications in futural practices. [ABSTRACT FROM AUTHOR]

Organic piezochromic materials that manifest pressure‐stimuli‐responses are important in various fields such as data storage and anticounterfeiting. The manipulation of piezofluorochromic behaviors for these materials is promising but remains a great challenge. Herein, a non‐luminous components regulated strategy is developed and organic molecular cages (OMCs), a burgeoning class of crystalline organic materials with structural dynamics, are first explored for the design of piezofluorochromic materials with tunable luminescence. A series of OMCs based on aggregation‐induced emission (AIE) chromophores, termed Cage 1–3, are synthesized and their piezofluorochromic behaviors are investigated by diamond anvil cell technique. Due to the sufficient voids between its flexible chromophores offered by the OMC structure, Cage 1 exhibits thermofluorochromic and piezofluorochromic properties. Moreover, the piezofluorochromic performance of this OMC could be further promoted by replacing its non‐luminous components with improved flexibilities, and a remarkable luminescence peak shift by 150 nm together with a response sensitivity of 13.8 nm GPa−1 was achieved upon hydrostatic compression. The cage structure plays a vital role in facilitating efficient and reversible piezofluorochromic behaviors. This study has shed light on the rational design and exploitation of OMCs as an exceptional platform to accomplish customizable piezofluorochromic behaviors and enlarge their potential applications in pressure‐based luminescence. [ABSTRACT FROM AUTHOR]

Lanthanide Single‐Molecule Magnets are fascinating objects that break magnetic performance records with observable magnetic bistability at the boiling temperature of liquid nitrogen, paving the way for potential applications in high‐density data storage. The switching of lanthanide SMM has been successfully achieved using several external stimuli such as redox reaction, pH titration, light irradiation or solvation/desolvation thanks to the high sensitivity of the magnetic anisotropy to any structural change in the lanthanide surrounding. Nevertheless, the use of applied high pressure as an external stimulus is largely underused, especially considering that it can be combined with high pressure X‐ray diffraction to establish a complementary structure‐property relationship. This Concept article summarizes the few relevant examples of investigations of lanthanide SMMs under applied high pressure, provides conclusions on the effect of such stimulus on molecular structures and magnetic anisotropy, and finally draws perspective on the future development of magnetic measurements under applied pressure. [ABSTRACT FROM AUTHOR]

By using complementary experimental methods including in situ high-pressure single-crystal X-ray diffraction and UV–Vis spectroscopy, the intricate connection between solvatochromism and solvatomorphism has been elucidated in a recent publication [Sobczak & Katrusiak (2024). IUCrJ, 11, 528–537]. The connection was demonstrated for an important pigment – Reichardt's dye – with potential applications in nonlinear optoelectronics and molecular pressure sensor development.

Fluorescence materials have attracted great attention in the last decades because of their modulable fluorescence properties and broad applications. Molecular packing is one of the most important factors that determines organic molecular piezochromic fluorescence behavior. Herein, we systematically investigated the fluorescence, vibrational, and structural properties of chrysene up to 20 GPa by using multiple experimental techniques and ab -initio calculations. We find the obvious color-changing with increasing pressure. Meanwhile, the phase transition at a pressure of about 6.6 GPa has been identified from both the frequency shifts and the changes in intensity of the Raman modes. However, the structure of chrysene at ambient pressure remains stable to at least P∼20.2 GPa from both experimental and theoretical x-ray diffraction results. Further structural analysis indicates that the angle between two molecular planes decreases with pressure, resulting in the packing alteration. The combined results from the experiments and computations demonstrated that the observed phase transition at 6.6 GPa is probably a result of the change of molecular packing. Furthermore, the intermolecular interactions have changed correspondingly due to the change of the molecular packing, which results in the color-changing of chrysene under pressure. These results provide further evidence that the intermolecular interactions play the important role in tuning the photo-physical properties, and this work will contribute to understanding the relationship between molecular packing and piezochromism in fluorescence materials. • The crystal optical color of chrysene undergoes obvious color-changing with increasing pressure. • The mode of molecular packing of chrysene has changed under pressure. • Piezochromic luminescence behavior of chrysene is result from the changes of intermolecular interactions. [ABSTRACT FROM AUTHOR]

By using complementary experimental methods including in situ high-pressure single-crystal X-ray diffraction and UV-Vis spectroscopy, the intricate connection between solvatochromism and solvatomorphism has been elucidated in a recent publication [Sobczak & Katrusiak (2024). IUCrJ, 11, 528-537]. The connection was demonstrated for an important pigment - Reichardt's dye - with potential applications in nonlinear optoelectronics and molecular pressure sensor development., (open access.)

Flexible crystals with plasticity and elasticity that exhibit phosphorescent emission are quite rare yet highly significant for their potential applications. In our study, we present an example of such flexible (both elastic and plastic) organic crystals based on 1,2-bis(3-bromophenyl)-ethane-1,2-dione (BBPED), which demonstrates a lifetime of 0.504 ms (517 nm) and a quantum efficiency of 26.12 % at room temperature. These crystals exhibit reversible elastic properties in both their original and twisted states, and possess optical waveguide properties with minimal optical loss coefficients in the range of 0.26–0.48 dB/mm. In addition, the above crystals exhibit phosphorescence to phosphorescence blueshift under hydrostatic pressure, whereas mechanical grinding produces a phosphorescence to phosphorescence redshift phenomenon. Theoretical calculations indicate that the alterations in molecular conformation and intermolecular interactions both contribute to the piezochromic phenomenon. In conclusion, this work provides a new approach to the design of multifunctional phosphorescent molecular crystals with flexible characteristics. • Flexible crystals with plasticity and elasticity. • Crystals with 1D to 3 D phosphorescent waveguide properties. • Crystals with piezochromism properties. [ABSTRACT FROM AUTHOR]

• Obvious luminescent piezochromism (62 nm). • Efficient thermochromism (80 to 300 K). • Multi-stimuli-responsive luminescence combines into one material. Luminescent coordination polymers (CPs) with one-dimensional (1D) closely-packed structures usually display poor performances in stimuli-responsive luminescence due to the low porosity and high rigidity. Here, we reported a multi-stimuli-responsive 1D luminescent [Cu 2 I 2 ]-cluster-based CP (CuIP-OPY) with piezochromic, thermochromic and oxygen sensing properties. Attributing to the flexibility of the OPY ligand, which twists under external forces and heating, respectively, CuIP-OPY shows obvious piezochromic and thermochromic luminescence. Moreover, although its porosity is only 1.1%, oxygen can still quench its luminescence intensity by 57.53%. To further confirm the related mechanism, we also synthesized a [Cu 2 Cl 2 ]-cluster-based CP with similar structure, namely CuClP-OPY, that displays higher rigidity, and compared the differences between these two CuXP-OPY (X = I, Cl) in the multi-stimuli-responsive behavior. [Display omitted] [ABSTRACT FROM AUTHOR]