Mild selective photochemical oxidation of an organic sulfide using OxP-polyimide porous polymers as singlet oxygen generators
Creators: name: Hynek, Jan
name: Payne, Daniel T.
name: Shrestha, Lok Kumar
name: Chahal, Mandeep K.
name: Ma, Renzhi
name: Dong, Jiang
name: Ariga, Katsuhiko
name: Yamauchi, Yusuke
name: Hill, Jonathan P.
Publisher: name: Taylor & Francis
Year: 2024
Subjects: subject: Biochemistry
subject: Medicine
subject: Genetics
subject: FOS: Biological sciences
subject: Neuroscience
subject: Evolutionary Biology
subject: Environmental Sciences not elsewhere classified
subject: Chemical Sciences not elsewhere classified
subject: Ecology
subject: Marine Biology
subject: Inorganic Chemistry
subject: FOS: Chemical sciences
subject: Infectious Diseases
subject: FOS: Health sciences
subject: Computational Biology

description: A series of porous organic polymers based on a singlet oxygen generating oxoporphyinogen (‘<b>OxP</b>’) has been successfully prepared from a pseudotetrahedral <b>OxP</b>-tetraamine precursor (<b>OxP(4-NH</b><sub><b>2</b></sub><b>Bn)</b><sub><b>4</b></sub>) by its reaction with tetracarboxylic acid dianhydrides under suitable conditions. Of the compounds studied, those containing naphthalene (<b>OxP-N</b>) and perylene (<b>OxP-P</b>) spacers, respectively, have large surface areas (~530 m<sup>2</sup> g<sup>−1</sup>). On the other hand, the derivative with a simple benzene spacer (<b>OxP-B</b>) exhibits the best <sup>1</sup>O<sub>2</sub> generating capability. Although the starting <b>OxP</b>-tetraamine precursor is a poor <sup>1</sup>O<sub>2</sub> generator, its incorporation into <b>OxP</b> POPs leads to a significant enhancement of <sup>1</sup>O<sub>2</sub> productivity, which is largely due to the transformation of NH<sub>2</sub> groups to electron-withdrawing diimides. Overall <sup>1</sup>O<sub>2</sub> production efficacy of <b>OxP-POP</b>s under irradiation by visible light is significantly improved over the common reference material <b>PCN-222</b>. All the materials <b>OxP-B</b>, <b>OxP-N</b> and <b>OxP-P</b> promote oxidation of thioanisole involving conversion of ambient triplet state oxygen to singlet oxygen under visible light irradiation and its reaction with the sulfide. Although the reaction rate of the oxidation promoted by <b>OxP</b> POPs is generally lower than for conventional materials (such as <b>PCN-222</b>) or previously studied <b>OxP</b> derivatives, undesired overoxidation of the substrate to methyl phenyl sulfone is suppressed. For organic sulfides, selectivity of oxidation is especially important for detoxification of mustard gas (bis(2-chloroethyl)sulfide) or similarly toxic compounds since controlled oxidation leads to the low toxicity bis(2-chloroethyl)sulfoxide while overoxidation leads to intoxification (since bis(2-chloroethyl)sulfone presents greater toxicity to humans than the sulfide substrate). Therefore, <b>OxP</b> POPs capable of promoting selective oxidation of sulfides to sulfoxides have excellent potential to be used as mild and selective detoxification agents. Oxoporphyrinogen (OxP) is a unique chromophore compound in that it is intrinsically de-aggregated allowing large quantum yields of singlet oxygen generation. Due to its structure, OxP is also an ideal building block for porous systems. In this work, we describe the first incorporation of OxP in highly stable microporous polymers strongly enhanced singlet oxygen generation for selective oxidation of organic sulfides to sulfoxides (as a model reaction) under heterogeneous conditions. The novelty of this work lies in the high stability and easy recovery of the materials, the synergetic enhancement of singlet oxygen generation in the polymers over the starting OxP, and the excellent selectivity for the oxidation reaction.