The ESR spectra of chromium (III) acetylacetonate in single crystals of cobalt (III) acetylacetonate and aluminum acetylacetonate were studied. In cobalt (III) acetylacetonate the spin Hamiltonian constants were found to have the values:g=1.9802plusmn;0.0005; verbar;Dverbar;=0.600plusmn;0.001 cmmdash;1; and verbar;Everbar;=0.0085plusmn;0.0005 cmmdash;1. In addition the outer two components of the hyperfine spectra due to Cr53was observed giving the values: verbar;Averbar; = (16.2plusmn;0.1)times;10mdash;4cmmdash;1and verbar;Bverbar;=(16.9plusmn;0.1)times;10mdash;4cmmdash;1. The resonance lines in the aluminum acetylacetonate host crystal were found to be broader, yielding less reliable but similar values for the spinhyphen;Hamiltonian constants. It is shown that the anisotropy in the hyperfine interaction can be explained by assuming the molecule to be slightly compressed along the trigonal axis.
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