Demonstration of the degeneracy of the singlet and triplet states in 2,3-dimethylenecyclohexane-1,4-diyl by measurement of its magnetic properties†

Abstract

Magnetic susceptibility and magnetization of 2,3-dimethylenecyclohexane-1,4-diyl (1), a conformationally restricted tetramethyleneethane (TME), have been investigated at 2–20 K and applied fields of 0–5 T. Theoretical curves for a model in which singlet and triplet states are in equilibrium were fitted to the experimental data. In contrast with a previous interpretation of the EPR signal intensities, singlet and triplet states were found to be almost degenerate (2|J/k_B| < 1 K), thus resolving a controversy as to the theoretical and experimental interpretation of the ground state of 1.