Dual-Channel-Mediated Spin Coupling for One-Electron-Oxidized Cobalt(II)-Saddled Porphyrin

Saddle-shaped CoII[OET­(p-R)­PP] (R = CF3, H, CH3) can be readily oxidized with Cl2, Br2, and I2 to the corresponding one-electron-oxidation product Co­[OET­(p-R)­PP]­X (X = Cl, Br, I) with the clear character of a ring cation radical. With the series of 1H and 13C NMR spectra of these related complexes, both the axial ligand and peripheral substituent of the ring macrocycle are proven to act as a dual channel to tune spin coupling between low-spin Co­(II) and a porphyrin π-cation radical. Density functional theory calculations have shown that the antiferromagnetic coupling between spins residing in dz2 and a2u are expected to exist as the ground state. The paramagnetic properties are attributed to an a1u-type ferromagnetic excited triplet state.