Versatile synthesis of chiral 6-oxoverdazyl radical ligands – new building blocks for multifunctional molecule-based magnets

Abstract

A versatile synthetic methodology to access the first family of chiral verdazyl N,N′-chelate ligands is described and exemplified by N,N′-dimethyl-, N,N′-di-isopropyl- and N,N′-diphenyl oxoverdazyls bearing two isomers of the pinene-pyridine functional group. Their physical properties were probed by X-band EPR spectroscopy, cyclic voltammetry and DFT calculations. Preliminary reactivity studies show they can act as N,N′-chelate ligands affording a chiral 1 : 1 complex (3b) with CuCl₂, which was characterized by single-crystal X-ray diffraction. Variable temperature EPR studies on (3b) confirm the presence of antiferromagnetic interactions between the spins of the Cu(II) ion and the verdazyl radical.