Preparation of a discotic 2,4,7,9‐tetraaryl‐6H‐dibenzo[c,e][1,2]thiazine and generation of a persistent Radical

Abstract

6H-Dibenzo [d,e][1,2]thiazine substituted with four 3,4-dioctyloxyphenyl groups forms a room temperature discotic phase with a clearing temperature of 104uC. Oxidation of the thiazine 2b with either metal oxides (PbO 2 or AgO) or SO 2 Cl 2 gave a moderately stable radical 1b (a N 50.95 mT, g52.0045). Full conversion of 2b to 1b was observed with AgO in a toluene/ MeCN mixture or with SO 2 Cl 2 . The radical 1b was isolated in the neat form with the latter oxidant. It shows sensitivity to molecular oxygen, which hampered its purification and subsequent thermal and magnetic studies.

Discotic Liquid Crystals

“…Furthermore, compound 201 underwent a reversible color change at the melting transition from red (λ max = 552 nm for Col h ) to green (λ max = 630 nm in the isotropic phase), which is very rare for radicals and indicates strong π–π*-absorption. In addition unsymmetrical 6-oxoverdazyls were studied, complemented by HOMO/LUMO calculations and cyclic voltammetry studies. , A discotic 2,4,7,9-tetraaryl- 6H -dibenzo­[ c,e ]­[1,2]­thiazine, which could be transformed into a persistent radical via oxidation, was also reported …”

Photoconductive Liquid-Crystalline Derivatives of 6-Oxoverdazyl

“…In this context, a number of thiazyl and thiazinyl derivatives have been synthesized and investigated as unidimensional semiconductors . Attempts to generate liquid-crystalline π-delocalized stable radicals were unsuccessful until recently. In 2009, Valesco and co-workers reported a carbazole derivative of triphenylmethyl radical that exhibits two columnar phases, quasi-reversible redox pairs with an electrochemical window of 1.5 V, a broad absorption spectrum in the visible region, and phase-dependent magnetic interactions between the cores.…”