| Autor: |
Nagelski AL; Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States., Ozerov M; National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States., Fataftah MS; Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States., Krzystek J; National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States., Greer SM; Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States., Holland PL; Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States., Telser J; Department of Biological, Chemical and Physical Sciences, Roosevelt University, Chicago, Illinois 60605, United States. |
| Abstrakt: |
The β-diketiminate supporting group, [ArNCRCHCRNAr] - , stabilizes low coordination number complexes. Four such complexes, where R = tert -butyl, Ar = 2,6-diisopropylphenyl, are studied: (nacnac t Bu )ML, where M = Fe II , Co II and L = Cl, CH 3 . These are denoted FeCl , FeCH 3 , CoCl , and CoCH 3 and have been previously reported and structurally characterized. The two Fe II complexes ( S = 2) have also been previously characterized by Mössbauer spectroscopy, but only indirect assessment of the ligand-field splitting and zero-field splitting (zfs) parameters was available. Here, EPR spectroscopy is used, both conventional field-domain for the Co II complexes (with S = 3/2) and frequency-domain, far-infrared magnetic resonance spectroscopy (FIRMS) for all four complexes. The Co II complexes were also studied by magnetometry. These studies allow accurate determination of the zfs parameters. The two Fe II complexes are similar with nearly axial zfs and large magnitude zfs given by D = -37 ± 1 cm -1 for both. The two Co II complexes likewise exhibit large and nearly axial zfs, but surprisingly, CoCl has positive D = +55 cm -1 while CoCH 3 has negative D = -49 cm -1 . Theoretical methods were used to probe the electronic structures of the four complexes, which explain the experimental spectra and the zfs parameters. |
