Porphyrin‐Based Air‐Stable Helical Radicals.

Abstract: Stable helical radicals are promising multi‐functional molecules in light of intriguing magnetic and chiroptical properties. Attempts were made to extend diphenylmethyl‐fused Ni^II porphyrin radical to helical system as the first air‐stable organic neutral helical radicals. Intramolecular Pd‐catalyzed twofold C−H arylation of methyl‐ or methoxy‐introduced <italic>meso</italic>‐diphenylmethyl Ni^II porphyrins gave a mixture of the target and rearranged radicals. Oxidative fusion reaction of <italic>meso</italic>‐(bis(1‐naphthyl)methyl) Ni^II porphyrins provided doubly fused Ni^II porphyrin radicals. One of the helical radicals was separated into enantiomers that showed mirror‐image circular dichroism (CD) spectra up to 1300 nm. The helical dinaphthylmethyl‐fused Ni^II porphyrin radical displayed solid‐state magnetic property mostly arising from monomeric radicals, different from the parent diphenylmethyl‐fused Ni^II porphyrin radical that showed antiferromagnetic coupling due to π‐stacked pairing. [ABSTRACT FROM AUTHOR]