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

摘要

A study of high- and low-spin cobalt(II) derivatives having hexadentate encapsulated ligands known as 'sar' is reported (sar=3,6,10,13,16,19-hexaazabicyclo(6.6.6)icosane). The chemically prepared derivatives have well defined EPR spectra at 4 K especially in the g=9 region, and were clearly high-spin Co(II). However, when the Co-II centres were prepared 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 free-spin region. These were converted into the normal high-spin form on annealing to similar to 115 K. [References: 14]