Singlet鈥揟riplet Gaps of Cobalt Nitrosyls: Insights from Tropocoronand Complexes

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• 作者：Kathrin H. Hopmann ; Jeanet Conradie ; Espen Tangen ; Zachary J. Tonzetich ; Stephen J. Lippard ; Abhik Ghosh
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：August 3, 2015
• 年：2015
• 卷：54
• 期：15
• 页码：7362-7367
• 全文大小：329K
• ISSN：1520-510X

文摘

A density functional theory (DFT) study of {CoNO}⁸ cobalt nitrosyl complexes containing the [n,n]tropocoronand ligand (TC-n,n) has revealed a sharp reduction of singlet鈥搕riplet gaps as the structures change from near-square-pyramidal (for n = 3) to trigonal-bipyramidal with an equatorial NO (for n = 5, 6). An experimental reinvestigation of [Co(TC-3,3)(NO)] has confirmed that it is not paramagnetic, as originally reported, but diamagnetic, like all other {CoNO}⁸ complexes. Furthermore, DFT calculations indicate a substantial singlet鈥搕riplet gap of about half an eV or higher for this complex. At the other end of the series, low-energy, thermally accessible triplet states are predicted for [Co(TC-6,6)(NO)]. Enhanced triplet-state reactivity may well provide a partial explanation for the failure to isolate this compound as a stable species.