Magnetic Properties of Tetrakis[4-(α -diazobenzyl)-pyridine]bis(thiocyanato-N)cobalt(II) in Frozen Solution after Irradiation. Formation of a Single-Molecule Magnet in Frozen Solution

Magnetic properties after irradiation of a 1:4 mixture of Co(SCN)₂ and 4-(α-diazobenzyl)pyridine in frozen solution were investigated by ac and dc magneto/susceptometry. Observations of the frequency dependence of X'' signals and of a hysteresis loop at 2 K in ac and dc measurements, respectively, indicate that the generated cobalt?carbene complex functions as a single-molecule magnet. This is the first example of a monometallic single-molecule magnet of nanometer size.