Magnetic properties of tetrakis[4-(alpha-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-(alpha-diazobenzyl)pyridine in frozen solution were investigated by ac and dc magneto/susceptometry. Observations of the frequency dependence of chi'' 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.