Small Nonplanar Phenothiazine‐ 5 ‐oxide‐Based Molecules: Structural Characterization, Photophysical, Thermal and Computational Studies

Abstract A series of novel non‐planar phenothiazine‐ 5 ‐oxides ( 2a ‐ l ) bearing electron donating, electron withdrawing and bulky groups has been synthesized in high yields and their structural, photophysical, thermal and electronic properties are investigated and compared. All compounds are blue and blue‐green emissive in solution (except 2g ) and solid state respectively. Single crystal X‐ray diffraction (XRD) studies of 2a , 2g , 2h , 2j and 2l indicated the effect of substituents on dihedral angles and non‐planarity of the molecules; 2g and 2j with m ‐nitrophenyl/ p ‐cyanophenyl as electron acceptor units exhibited “push‐pull” behaviour with more planar structures, and D (donor) to A (acceptor) π‐stacking interactions which was also evidenced by solvatochromic and DFT studies. Thermal gravimetric analysis (TGA) indicated good thermally stability of these compounds with thermal decomposition temperatures (T d ) in the range of 194‐306 °C. Density functional theory (DFT) and time‐dependent DFT approaches were employed to study the HOMO, LUMO and energy gap of these compounds.