Oxidation State Tuning of Room Temperature Phosphorescence and Delayed Fluorescence in Phenothiazine and Phenothiazine‐5,5‐dioxide Dimers

Abstract

Heterocyclic dimers consisting of combinations of butterfly‐shaped phenothiazine (PTZ) and its chemically oxidized form phenothiazine‐5,5‐dioxide (PTZ(SO2)) have been synthesized. A twist is imposed across the dimers by ortho‐substituents including methyl ethers, sulfides and sulfones. X‐ray crystallography, cyclic voltammetry and optical spectroscopy, underpinned by computational studies, have been employed to study the interplay between the oxidation state, conformational restriction, and emission mechanisms including thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP). While the PTZ(SO2) dimers are simple fluorophores, the presence of PTZ induces triplet‐mediated emission with a mixed PTZ‐PTZ(SO2) dimer displaying concentration dependent hallmarks of both TADF and RTP.

Points of Interest in the Chemistry of the Levomepromazine Drug Substance: Recycling of Undesired Enantiomer, Identification of New Phenothiazine Dimers, Synthesis of a Pharmacopeial Impurity, and an Unexpected Rearrangement

“…It is known that phenothiazine and its derivatives act as single electron donors upon contact with oxidizing agents, and the radical formed from compound 2 after deprotonation ( 10 , Scheme ) can dimerize and oligomerize . While compounds 8 and 9 themselves are new, type 8 dimers, in which the monomers are linked by a C–N bond (bearing substituents other than methoxy groups on the aromatic rings), have been described earlier. − The formation of N , N′ -dialkylated derivatives of dimer 9 has also been disclosed. , …”

“…26−30 The formation of N,N′-dialkylated derivatives of dimer 9 has also been disclosed. 31,32 Given the dimerization and polymerization tendency of phenothiazines known from the literature, [25][26][27][28]30 we decided to investigate whether dimers 8 and 9 would be formed when stirring phenothiazine 2 in THF in the presence of t-BuOK at room temperature. 30 As expected, a complex product mixture was formed, from which dimer 8 could be successfully separated by chromatography (Scheme 6).…”

Design, synthesis, structure elucidation, antimicrobial, molecular docking, and SAR studies of novel urea derivatives bearing tricyclic aromatic hydrocarbon rings

“…[38] Phenothiazine and its substitutions constitute a unique tricyclic core of heterocyclic compounds which have been investigated to find different applications in medicine and industry. [39][40][41] They have been established among natural products, such as the siderophore pyochelin, [42] phenazine-1carboxylic acid, [43] and the blue pigment pyocyanin. [44] Phenothiazine derivatives are widely used as building skeletons for the preparation of biologically active compounds.…”