Crystal Engineering Using Polyiodide Halogen and Chalcogen Bonding to Isolate the Phenothiazinium Radical Cation and Its Rare Dimer, 10-(3-Phenothiazinylidene)phenothiazinium

Chemistry. 2021 Jun 4;27(32):8398-8405. doi: 10.1002/chem.202100730. Epub 2021 May 5.

Abstract

Utilizing facile one-electron oxidation of 10H-phenothiazine by molecular diiodine, the solid-state structure of the 10H-phenothiazinium radical cation was obtained in three cation:iodide ratios, as well as its THF and acetone solvates. Oxidation of 10H-phenothiazine with molecular diiodine in DMSO or DMF provided the structure of the radical coupling product 10-(3-phenothiazinyldene)phenothiazinium, which has not been crystallographically characterized to date. The radical cations were balanced by a mixture (I7 )- , (I5 )- , (I3 )- , and I- anions, where a variety of chalcogen, halogen, and hydrogen bonding interactions stabilize the structures to reveal these interesting cationic species.

Keywords: X-ray diffraction; chalcogen bonding; crystal engineering; halogen bonding; stacking interactions.