Unveiling the mysterious hydrocarbon – Clar’s goblet

Abstract

In the classic view, spin pairing occurs between two electrons in a chemical bond where the bonding interaction compensates for the penalty of electrostatic repulsion. It is a mystery whether spin pairing can occur between two non-bonded electrons within a molecular entity. Unveiling this elusive spin entanglement (i.e., pairing between two spatially segregated spins) at the molecular scale, is a long-standing challenge. Clar’s goblet proposed by Erich Clar in 1972, provides an ideal model to verify this unusual property. Here, we report the solution-phase synthesis of Clar’s goblet and experimental elucidation of its spin properties. Magnetic studies reveal that the two spins are spatially segregated with an average distance of 8.7 Å, and antiferromagnetically coupled in the ground state with an ES-T of –0.29 kcal/mol. Our results provide direct evidence of spin entanglement in the Clar’s goblet and may inspire the design of correlated molecular spins for quantum information technologies.