Multichromophoric Cyclotriphosphazene Architecture: Integrating Phenothiazine and Phenylhydrazone Frameworks for Tunable Optoelectronic Properties

ABSTRACT

We report the synthesis, characterization, and photophysics of an unprecedented hybrid inorganic‐organic hydrazone Schiff base, CTP‐π‐PTZ, featuring a central cyclotriphosphazene (CTP) ring linked to six phenothiazine (PTZ) units through aminobenzoate (PABE) aromatic spacers. Nucleophilic substitution of six PABE units onto the CTP ring yielded an aromatic ester intermediate, which was converted into a hydrazide and subsequently condensed with six equivalents of phenothiazine aldehyde (R–PTZ–CHO) to afford the target hexakis Schiff base assembly, CTP‐π‐PTZ. To evaluate the impact of the CTP core on photophysical properties, a CTP‐free control Schiff base (SB–PTZ) was also synthesized. Compared to SB–PTZ, the hybrid CTP‐π‐PTZ exhibited a hypsochromic (blue) shift in absorption alongside a bathochromic (red) shift in its broad emission profile, highlighting the influence of the central inorganic core. Thermogravimetric analysis (TGA) confirmed high thermal stability for CTP‐π‐PTZ, while solvatochromic photoluminescence studies demonstrated pronounced intramolecular charge transfer (ICT) dynamics. The molecular structures, photophysical, and electrochemical properties were comprehensively characterized using FT–IR, multinuclear NMR ( ³¹ P, ¹ H, and ¹³ C), ESI‐HRMS, cyclic voltammetry, UV–vis spectroscopy, photoluminescence, and time‐resolved photoluminescence studies.