Triarylmethanols with Bulky Aryl Groups and the NOESY/EXSY Experimental Observation of a Two‐Ring‐Flip Mechanism for the Helicity Reversal of Molecular Propellers

Abstract

Triarylmethanols - the direct precursors of persistent trityl radicals - are racemic mixtures of chiral three-bladed molecular propellers. Depending on bulkiness of aryl groups they exhibit various liabilities to interconversion, the half- life time of room temperature racemization varying in a range between 8.4 hours and 1.32 years. NOESY/EXSY experiment performed on two representative models strongly supports the two-ring flip mechanism for the configurational interchange.