A two-step approach to the synthesis of N@C60fullerene dimers for molecular qubits

Abstract

We report the two-step synthesis of a highly soluble fullerene dimer, both for short reaction times and at the microscale. We apply this reaction scheme to starting materials that contain ¹⁵N@C₆₀ and ¹⁴N@C₆₀, and we demonstrate how, if applied to highly pure N@C₆₀ in the future, this scheme may be used to produce (¹⁴N@C₆₀)₂ or (¹⁵N@C₆₀)₂ dimers in one step, and crucially ¹⁴N@C₆₀–¹⁵N@C₆₀ dimers in a second step. Such dimers represent isolated electron spin pairs that may be used to demonstrate entanglement between the spins. Additionally, CW EPR spectroscopy of the ¹⁵N@C₆₀–C₆₀ dimer in the solid state reveals permanent zero-field splitting (D = 14.6 MHz and E = 0.56 MHz).