A novel [2.2]paracyclophane bridged TTM-diradical and its interaction with circularly polarized light

Abstract

Chiral diradicals that interact with light represent interesting molecules with potential application in quantum technology. Here, we report the synthesis of such a novel tris(2,4,6-trichlorophenyl)methyl derived diradical, which is coupled to a chiral bis-acetylene [2.2]paracyclophane using Sonogashira cross-coupling. The optical properties are compared with a non-chiral [2.2]paracyclophane diradical homologue and a phenylacetylene tris(2,4,6-trichlorophenyl)methyl radical reference compound. We study the weak electronic and magnetic interactions between the two unpaired electrons and the chiroptical properties of the diradicals. The enantiomers of the chiral diradical are separated via chiral HPLC and studied by circular dichroism. Magnetic characterization reveals triplet state population, due to near-degenerate singlet-triplet energy levels with a vanishingly small splitting (ΔEST < 0.1 kJ mol-1), consistent with results from DFT calculations.