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Inkless and erasable printing (IEP) based on chromic materials holds great promise to alleviate environmental and sustainable problems. Metal–organic polymers (MOPs) are bright platforms for constructing IEP materials. However, it is still challenging to design target MOPs with excellent specific functions rationally due to the intricate component‐structure‐property relationships. Herein, an effective strategy was proposed for the rational design IEP‐MOP materials. The stimuli‐responsive viologen moiety was introduced into the construction of MOPs to give it potential chromic behaviors and two different coordination models (i. e. bilateral coordination model, M1; unilateral coordinated model, M2) based on the same viologen ligand were designed. Aided by theoretical calculations, model M1 was recommended secondarily as a more suitable system for IEP materials. Along this line, two representative viologen‐ZnII MOPs 1 and 2 with models M1 and M2 were synthesized successfully. Experiments exhibit that 1 does have quicker stimuli response, stronger color contrast and longer radical lifetime compared to 2. Significantly, the obtained 1‐IEP media brightly inherits the excellent chromic characteristics of 1 and the flexibility of the paper at the same time, which achieves most daily printing requirements, as well as enough resolution and durability to be used in identification by smart device. [ABSTRACT FROM AUTHOR]

A library of β-enamino diketones was prepared via base-mediated, three-component reaction of 4-hydroxycoumarins with various aromatic/aliphatic amines and β-nitrostyrenes under microwave irradiation conditions to investigate their photochemical properties. Among the prepared compounds, a thiophene derived β-enamino diketone was found to be light-sensitive and to exhibit unique photochromic behavior, that is, positive photochromism in solution and negative photochromism in crystalline phase. In addition, this prepared photochromic compound was further covalently linked to a structure-related, piezochromic β-enamino diketone moiety to explore its potential multi-stimuli responsive properties.

Halide perovskite materials stand out in the field of photoelectricity because of their excellent luminescence and variable discoloration luminescence properties, which is mainly due to their diverse phase transition phenomenon of halide perovskites and their derivatives materials. This work focused on the introduction of various phase-transition chromotropic properties of halide perovskite materials, including photochromism, piezochromism and thermochromic properties. The intrinsic phase-transition mechanism of the chromotropic properties induced by various external factors is mainly analyzed. Finally, the future research and application prospects of the chromotropic properties of halide perovskite materials are discussed. [ABSTRACT FROM AUTHOR]

The review is devoted to mechanically sensitive indoline spiropyrans and their structural features. Recent advances in the study of their isomerization processes are considered, special attention is paid to the effect of pressure on the behavior of spiropyrans in the composition of various photochromic materials and dyes, as well as in the process of the formation of J-aggregates in Langmuir–Blodgett films. [ABSTRACT FROM AUTHOR]

Abstract The iso -cis/trans-aminobenzopyranoxanthenes (iso -cis/trans-ABPXs), as one of popular leuco dyes, were investigated in solution or crystal phase. The introduction of benzo-pentacyclic-ester group in iso -cis/trans-ABPXs leads to remarkable multi-stimuli responsive behaviors, including protonation effect, photochromism and piezochromism with notable color changes. The iso -cis/trans-ABPXs show different in the responsive sensitivity and the iso -cis-ABPX is highly sensitive to environmental stimuli relative to the trans-form, which can be explained by their different C-H⋯O interaction and/or C-O bond length. Interestingly, as the ultraviolet light irradiation time increasing, the iso -cis/trans-ABPXs solution gradually becomes transparent and orange precipitates are achieved, which is identified as iso -ABPXs±. Multi-stimuli responsive behaviors on the iso -cis/trans-ABPXs provide a comprehensive insight into the chromogenic mechanisms of this type of materials, suggesting that they may be potential candidate materials for sensors and indicators. Graphical abstract Image 1 Highlights • The iso -cis/trans-ABPXs show remarkable color and spectral changes under different stimuli respectively. • The iso -cis -ABPXs is more sensitive to the stimuli due to the differences in structures. • The orange solid of iso -cis/trans-ABPXs± can be produced from iso -cis/trans-ABPXs solution under the UV light irradiation. [ABSTRACT FROM AUTHOR]

A novel carbazole-substituted naphthopyran, 3,3-bis-(4-carbazolylphenyl)-[3H]-naphtho[2,1-b]pyran (CzNP) was designed and synthesized. The new compound exhibited normal photochromism in dichloromethane solution and the UV irradiation did not influence its fluorescence. On the contrary, the fluorescence of CzNP in N,N-dimethylformamide (DMF) was intensively enhanced to 29 times after 60 min of the UV irradiation and this enhanced fluorescence can be quenched by addition of triethylamine (TEA). The study of enhanced extent of fluorescence of CzNP in solvents with different polarities and in mixed solvents demonstrated that the enhanced fluorescence is dependent on the polarity of solvents. The larger the polarity of solvent was, the stronger was the fluorescence of CzNP. CzNP also exhibited piezochromic performance and the pressure led to the cleavage of the C–O bond of pyran ring. [ABSTRACT FROM AUTHOR]

A multifunctional bis-imidazole derived from piperonal was prepared and found to have photo, thermo, solvato and peiezochromism with colour changes from pale green to deep blue. The multifunctionality colour changes and stability of the coloured species make the derivative candidates for various applications such as optical data storage. The photochromic properties and performance were found to be affected remarkably upon changing the solvent. [ABSTRACT FROM AUTHOR]