A Redox-Active Bridging Ligand to Promote Spin Delocalization, High-Spin Complexes, and Magnetic Multi-Switchability

A dinuclear Co-II complex, [Co-2(tphz)(tpy)(2)](n+) (n = 4, 3 or 2; tphz: tetrapyridophenazine; tpy: terpyridine), has been assembled using the redox-active and strongly complexing tphz bridging ligand. The magnetic properties of this complex can be tuned from spin-crossover with T-1/2 approximate to 470 K for the pristine compound (n = 4) to single-molecule magnet with an S-T= 5/2 spin ground state when once reduced (n = 3) to finally a diamagnetic species when twice reduced (n = 2). The two successive and reversible reductions are concomitant with an increase of the spin delocalization within the complex, promoting remarkably large magnetic exchange couplings and high-spin species even at room temperature.