Strong ferromagnetic metal-ligand exchange in a nickel bis(3,5-dipyridylverdazyl) complexElectronic supplementary information (ESI) available: Experimental details of the synthesis of 1 and 5 including 1H and 13C NMR spectra of 3 and 4. CCDC 753408. For ESI and crystallographic details in CIF or other electronic format see DOI: 10.1039/c0cc02233k

A new 1,5-dipyridyl verdazyl, synthesized from the corresponding dipyridyl hydrazone, coordinates nickel( ii ) to form a structurally characterized, pseudooctahedral complex analogous to Ni(terpy) 2 2+ . The unusually short Ni-verdazyl distance results in strong ferromagnetic exchange ( J Ni-rad = +300, J rad-rad = +160 cm −1 ) between all three paramagnetic species along with a metal-ligand charge transfer band in the electronic spectrum. The nickel complex of a verdazyl radical with two chelating 'arms' exhibits a short metal-radical distance and very strong ferromagnetic exchange between the metal and coordinated radicals.