Multi-Stimuli Response Displaying Novel Phenothiazine-Based Non-Planar D-p-A Hydrazones: Synthesis, Characterization, Photophysical and Thermal studies

摘要

Multi-stimuli responsive non-planar D-p-A hydrazones bearing non-planar phenothiazine as donor (D) and benzothiazole and dinitrophenyl rings as acceptor (A) were synthesized and their structural, photophysical, thermochromic, mechanofluorochromic (MFC) and acidochromic properties were studied. Thermal gravimetric analysis (TGA) and spectrophotometric studies revealed higher thermal stability, better ICT character and enhanced D-A intramolecular interactions in phenothiazine hydrazone bearing phenyl pendant ring. Hydrazones bearing benzothiazole ring as A displayed aggregation induced emission enhancement (AIEE) as well as acidochromism in presence of volatile acids like TFA. Greater extent of change in color and emission wavelength under external pressure revealed better MFC behavior of phenothiazine hydrazone bearing phenyl pendant ring. Two of the hydrazones exhibited reversible mechanofluorochromism on fuming their ground samples with DCM vapors. Structure-property relationship studied by single crystal X-ray diffraction patterns suggested the existence of twisted molecular conformation and weak intermolecular interactions such as p–p, C-H–p and S–S which played a vital role in the phase transition from crystalline to amorphous state under mechanical stress which was further justified by powder X-ray diffraction patterns.