EPR Active Supramolecular Gel With Network Fabrication: Selective H₂O₂ Induced EPR Enhancement From a Soft Gel

Supramolecular gels have been developed with flexible network to stabilize species such as flavin mononucleotide hydride with extraordinary short lifetime. In this work, we targeted to stabilize our synthesized radical CP• (chromenopyridine) in the supramolecular gel network. The rigidity aspects of EPR active multicomponent supramolecular gels were addressed. The gels were obtained from the combination of air stable carbon centered radical DCP• (dicyanomethylchromenopyridine) and diverse range of aromatic di-/tri-amine in DMSO and water mixture. During the gel formation, DCP• was converted into another EPR active molecule CP•. Interestingly, poor solubility of CP• restricted its direct use in the gel formation with the same set of amines from the similar DMSO and water mixtures. The rheological properties and morphologies of the gels were completely dependent upon the amine nature and solvent ratio. EPR activities of the rigid supramolecular gels remained stable even after H₂O₂ treatment. In the case of a selective soft gel with benzene-1,3,5-triamine (3), the EPR intensity selectively enhanced after the H₂O₂ treatment, due to the formation of DCPC• formed by reaction of DCPH and in situ formed hydroxyl radical. This radical formation was further validated by the detection of CP-OH adducts from other gel, as confirmed by mass spectrometry.