In a previous study, we reported (1) the thermal dependence of the crystallography of the tris-acetylacetonates of Al, Ti, V, Cr, Mn, Fe and Co (e.g., polymorphism) over the range of 100-300 K. In the process of preparing that report, we were reminded that those substances undergo thermal or vis-UV induced decomposition into free radicals (of unstated composition) useful in initiating polymerization of materials such as styrene (2,3). The fact that free radicals were formed by such thermal or vis-UV induced phenomena was already documented by Bernal (4), who could not identify the product(s) generated thus because the esr lines were very broad, probably due to the presence of more than one paramagnetic species. Therefore, we extended that study by DSC and combined DSC/TG/MS analyses over the range of 100 K to the (decomposition) point using only of Al, Cr, Mn, Fe and Co because Ti and V are very unstable outside a glove box. TG indicates that Co, Al, Cr and Fe complexes lose weight in one broad transition while the Mn sample changes in two well defined processes, separated by about 100?C. Mass spectrometry records large numbers of ions, several of which are readily identified as the predicted free radicals.
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