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

A dinuclear CoII complex, [Co2 (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 T1/2 ≈470 K for the pristine compound (n=4) to single-molecule magnet with an ST =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.