Electronic and spin delocalization in a switchable trinuclear triphenylene trisemiquinone bridged Ni 3 complex

A trinuclear triphenylene trisemiquinone complex containing paramagnetic Ni II is obtained under ambient conditions from the reaction of deprotonated tricatecholate hexahydroxytriphenylene (H 6 HHTP) with Ni II capped with a trispyrazolyl borate tridentate ligand. The magnetic and EPR data are consistent with delocalization of the electronic spin over the three Ni II species. The two-electron reduced complex shows an EPR spectrum corresponding to a S = 1/2 species due to a large antiferromagnetic coupling between the radical and only one of the Ni II ions highlighting the localization of the electronic spin. No EPR signal is observed for the one- and three-electron reduced species consistent with the closed shell of the bridging ligand.