Magnetic properties after irradiation of tetrakis[4-(α-diazobenzyl)pyridine] copper(II) in a frozen solution

The molecular structure of tetrakis[4-(α-diazobenzyl)pyridine]copper(II) bis(hexafluorophosphate) was revealed by X-ray structure analysis. The magnetic properties after irradiation of a 1:4 mixture of Cu(NO₃)₂ and 4-(α-diazobenzyl)pyridine in frozen ethanol solutions were investigated by electron paramagnetic resonance (EPR) spectrometry and magneto/susceptometry. In a randomly oriented X-band EPR spectrum, new signals appeared in the field range of 0-500 mT at the expense of the signals due to the isolated copper(II) after irradiation. All signal intensities gradually decreased on warming and new signals disappeared over 60 K. The field dependence of difference magnetization M at 2 and 5 K was measured under a condition similar to that for the EPR experiment. Fitting experiments to M vs. H/T plots by use of theoretical equations for two components suggested that a mixture of high-spin species with S = 9/2 and 7/2 in a ratio of 0.18:0.82 formed under a frozen condition.