EPR-SPECTRA FOR HIGH-SPIN AND LOW-SPIN CO-II ENCAPSULATED COMPLEXES

A study of high- and low-spin cobalt(II) derivatives having hexadentat e encapsulated ligands known as 'sar' is reported sar=3,6,10,13,16,19- hexaazabicyclo(6.6.6)icosane). The chemically prepared derivatives hav e well defined EPR spectra at 4 K especially in the g=9 region, and we re clearly high-spin Co(II). However, when the Co-II centres were prep ared by radiation-induced electron addition to the Co(III) complex at 77 K, a low-spin species was initially formed with g values in the fre e-spin region. These were converted into the normal high-spin form on annealing to similar to 115 K.