Counter-Rotating Spin-Polarised Ring Currents in Odd-Electron Carbocycles



We propose a molecular-orbital model to explain how majority and minority spins in odd-π-electron carbocycles sustain counter-rotating magnetic-field-induced ring currents. The model is based on the ipsocentric approach to magnetic response, in which ring currents are dominated by frontier-orbital contributions obeying angular-momentum selection rules. Coupled unrestricted Hartree–Fock ab initio calculations of the ring-current responses for singly charged benzene and planarised cyclo-octatetraene ions confirm the predictions of the qualitative model, and are consistent with correlated MP2 spin-polarised current calculations.