Synthesis of Fe(II) & Co(II) Verdazyl Ligand Complexes

Stable free radicals can be used as spin probes as well as having potential application as molecular devices and switches. Verdazyls are stable radicals with a large potential for structural diversity, since they carry three potential variable substituent’s that give a variety of different structures and two nitrogen atoms capable of coordinating metal ions.  The nitrogen atoms contain the bulk of the spin density and this particular property gives strong magnetic interaction between metal and radical, giving us the potential to form extended metal-organic structures with unusual magnetic properties.  We hypothesize that verdazyl radicals with two pyridyl substituents should coordinate with transition metals (Fe²⁺ & Co²⁺) analogously to a terpyridine ligand and that the resulting complexes will have unusual electronic structure as a result of the metal-radical interaction.   Bis(1-isopropyl-3,5-3,5-di(2’-pyridyl)-6-oxoverdazyl)iron(II) hexafluorophosphate  was synthesized in three steps from Pyridine-2-carboxaldehyde-2’-pyridylhydrazone (papyH).  The identity of the verdazyl complex was confirmed by Electron Spin Resonance (ESR), UV-vis, mass spectrometry, IR and X-ray crystallography  Structural data also confirmed the analogy with terpyridine.  Further research studies will be conducted upon the Cobalt(II) ligand complex, to determine how it compares to the Iron(II) complex. This research was supported in part by the MARC program (MARC U*STAR at SJSU).