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Reversible Tricolor Mechanochromic Luminescence in Anthranyl π‐Conjugates by Varying the Number of Methoxy Substituents: A Structure‐Property Relationship Study
Author(s) -
Prusti Banchhanidhi,
Aggarwal Himanshu,
Chakravarty Manab
Publication year - 2020
Publication title -
chemphotochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.13
H-Index - 18
ISSN - 2367-0932
DOI - 10.1002/cptc.201900299
Subject(s) - luminescence , intermolecular force , phenothiazine , alkyl , materials science , photoluminescence , fluorescence , photochemistry , differential scanning calorimetry , crystallography , crystal structure , exothermic reaction , molecule , chemistry , optoelectronics , organic chemistry , optics , medicine , physics , pharmacology , thermodynamics
Abstract Considering the demand and challenges ahead in the development of new and easily accessible small molecules as mechano(piezo)fluorochromic aggregation‐induced emission active fluorogens (PAIEgens), 1,3,5‐trimethoxybenzene is conveniently connected to anthracene and linked to mono‐ N ‐alkyl‐phenothiazine with different alkyl chain lengths via a facile, low‐cost and metal‐free synthetic route. These unsymmetrical π‐conjugates are established as small blue‐shifted AIEEgens (AIEE=aggregation‐induced enhanced emission) that exhibit tricolor switching with a sharp PL (photoluminescence or fluorescence) color change (48 nm red‐shift) from green‐to‐yellow on grinding and yellow‐to‐reddish upon thermal annealing at 150 °C. The color change is found to be reversible on exposure to solvent vapor. The role of the trimethoxy groups and N ‐alkylphenothiazine core to achieve PAIEE is demonstrated by analyzing its molecular structure and crystal packing with various intermolecular interactions. The structure‐property relationship study shows the significant role of the combination of trimethoxy groups and phenothiazine cores for this system. A variation on the destruction and creation of different crystal facets under different external stimuli are identified through powder X‐ray diffraction studies. The existence of different metastable states is also captured by the appearance of exothermic peaks in the differential scanning calorimetry experiments. Such PAIEgens are shown to be useful as a platform with “write‐erase‐write” functions in security writing and anti‐counterfeiting applications under external stimuli.