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Trends in metal-biradical exchange interaction for first-row M-II(nitronyl nitroxide-semiquinone) complexesстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 17 декабря 2015 г.
- Авторы: Shultz D.A., Vostrikova K.E., Bodnar S.H., Koo H.J., Whangbo M.H., Kirk M.L., Depperman E.C., Kampf J.W.
- Журнал: Journal of the American Chemical Society
- Том: 125
- Номер: 6
- Год издания: 2003
- Издательство: American Chemical Society
- Местоположение издательства: United States
- Первая страница: 1607
- Последняя страница: 1617
- DOI: 10.1021/ja020715x
- Аннотация: We report molecular structures and temperature-dependent magnetic susceptibility data for several new metal complexes of heterospin triplet ground-state biradical ligands. The ligands are comprised of both nitronyl-nitroxide (NN) and serniquinone (SQ) spin carriers. Five compounds are five-coordinate M-11 complexes (M = Mn, Co, Ni, Cu, and Zn), and one is a six-coordinate Ni-11 complex. Five compounds were structurally characterized. During copper complex formation a reaction with methanol occurs to form a unique methoxy-substituted SQ ring. Variable-temperature magnetic susceptibility studies are consistent with strong intraligand (NN-SQ and NN-PhSQ) ferromagnetic exchange coupling. For the five-coordinate Mn, Co, and Ni complexes, the S = I ligand is antiferromagnetically coupled to the metal. For both the five-coordinate Cu complex and the six-coordinate Ni complex, the ligand is ferromagnetically coupled to the metal spins in accordance with orbital symmetry arguments. Despite the low molecular symmetries, the predicted trend in metal-ligand exchange interactions is supported by spin dimer analysis based on extended Huckel calculations. For (NN-SQ)NiTp(Cum,Me) (Tp(Cum,Me) = hydro-tris(3-cumenyl-5-methylpyrazolyl)borate), an antisymmetric exchange term was required for the best fit of the magnetic susceptibility data. Antisymmetric exchange was less important for the other complexes due to inherently smaller Deltag. Finally, it is shown that intraligand exchange coupling is of paramount importance in stabilizing high-spin states of mixed metal-biradical complexes.
- Добавил в систему: Vostrikova Kira E.