SET and HAT/PCET acid‐mediated oxidation processes in helical shaped fused bis‐phenothiazines

Abstract

species of helicenes 1-9 have been measured and calculated to afford a complete rationalization of the redox behaviour of these appealing chiral compounds.

Methods to Determine Chain-Breaking Antioxidant Activity of Nanomaterials beyond DPPH•. A Review

“…In the presence of HOO • , nitroxides and ortho-quinone [36] containing molecules (indicated with Q in Scheme 1) behave as catalytic antioxidants causing the disappearance of ROO • and HOO • with little antioxidant consumption [82,83]. The reaction between an RTA antioxidant and ROO • can occur through a variety of sequential or concerted proton-coupled electron transfer mechanisms that are important to rationalize the antioxidant effect in any given reaction medium [84][85][86]. In general, antioxidants having a low bond dissociation enthalpy of the O-H or N-H bonds or low redox potential react quickly with ROO • but at the same time are susceptible to react with O 2 .…”

Resolution of a Configurationally Stable Hetero[4]helicene

“…DTA [4]H are obtained [17][18][19][20][21], as racemic mixture, from properly substituted Circular dichroism (CD) and circularly polarized luminescence (CPL) are just a few of the chiroptical proprieties that make helicenes valuable in potential applications such as advanced optical information storage, circularly polarized organic light-emitting diodes (CP-OLEDs), circularly polarized light detecting organic field effect transistors (CP-OFETs), chirality-induced spin selectivity (CISS) devices and stereoselective sensing chiroptical probes in biological processes [3][4][5][6][7][8][9][10][11][12][13][14].…”

“…DTA [4]H are obtained [17][18][19][20][21], as racemic mixture, from properly substituted triarylamines (TAA) 2 or N-aryl phenothiazines (PTZ) 3 (Scheme 1, pathway A and B respectively), through regioselective sulfenylation(s) with two or one equivalents of phthalimidesulfenyl chloride (PhtNSCl (4), Pht = phthaloyl). Reacting the resulting sulfenylated derivatives 5 or 6 with a Lewis Acid (L.A.), typically BF3OEt2 or AlCl3, causes two or one electrophilic intramolecular cyclization with formation of helicenes 1.…”

“…Reacting the resulting sulfenylated derivatives 5 or 6 with a Lewis Acid (L.A.), typically BF3OEt2 or AlCl3, causes two or one electrophilic intramolecular cyclization with formation of helicenes 1. Along with their peculiar helical-shaped structure, derivatives 1 show a very good one-electron donor ability, being easily, and reversibly, oxidized to the corresponding DTA [4]H are obtained [17][18][19][20][21], as racemic mixture, from properly substituted triarylamines (TAA) 2 or N-aryl phenothiazines (PTZ) 3 (Scheme 1, pathway A and B respectively), through regioselective sulfenylation(s) with two or one equivalents of phthalimidesulfenyl chloride (PhtNSCl (4), Pht = phthaloyl). Reacting the resulting sulfenylated derivatives 5 or 6 with a Lewis Acid (L.A.), typically BF 3 OEt 2 or AlCl 3 , causes two or one electrophilic intramolecular cyclization with formation of helicenes 1.…”

“…Along with their peculiar helical-shaped structure, derivatives 1 show a very good one-electron donor ability, being easily, and reversibly, oxidized to the corresponding exceptionally stable crystalline chiral radical cations 1 •+ [18,21] (Scheme 2). We have also demonstrated that the oxidative process is extremely sensitive to the medium, and under acidic conditions, molecular oxygen becomes an efficient single electron transfer (SET) oxidant, giving rise to the formation of exceptionally stable crystalline chiral radical cations 1 •+ [18,21] (Scheme 2). We have also demonstrated that the oxidative process is extremely sensitive to the medium, and under acidic conditions, molecular oxygen becomes an efficient single electron transfer (SET) oxidant, giving rise to the formation of 1 •+ .…”