Spectroscopic and Computational Investigations of a Mononuclear Manganese(IV)-Oxo Complex Reveal Electronic Structure Contributions to Reactivity.
The mononuclear Mn(IV)-oxo complex [Mn(O)(N4py)], where N4py is the pentadentate ligand N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine, has been proposed to attack C-H bonds by an excited-state reactivity pattern [Cho, K.-B.; Shaik, S.; Nam, W. J. Phys. Chem. Lett. 2012, 3, 2851-2856 (DOI: 10....
| Publicado en: | Journal of the American Chemical Society Vol. 138; no. 47; pp. 15413 - 15425 |
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| Autores principales: | , , , |
| Formato: | Artículo |
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American Chemical Society
11/30/2016
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| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=119918065&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 119918065 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 11/30/2016 vid: 138 iid: 47 pid: 997 pub: American Chemical Society artinfo: ui: 119918065 10.1021/jacs.6b08661 ppf: 15413 ppct: 12 formats: tig: atl: Spectroscopic and Computational Investigations of a Mononuclear Manganese(IV)-Oxo Complex Reveal Electronic Structure Contributions to Reactivity. aug: au: Leto, Domenick F. Massie, Allyssa A. Rice, Derek B. Jackson, Timothy A. affil: Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States su: Ligands (Chemistry) Carbon-hydrogen bonds Density functional theory Magnetic circular dichroism Circular dichroism sug: subj: Ligands (Chemistry) Carbon-hydrogen bonds Density functional theory Magnetic circular dichroism Circular dichroism ab: The mononuclear Mn(IV)-oxo complex [Mn(O)(N4py)], where N4py is the pentadentate ligand N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine, has been proposed to attack C-H bonds by an excited-state reactivity pattern [Cho, K.-B.; Shaik, S.; Nam, W. J. Phys. Chem. Lett. 2012, 3, 2851-2856 (DOI: 10.1021/jz301241z)]. In this model, a E excited state is utilized to provide a lower-energy barrier for hydrogen-atom transfer. This proposal is intriguing, as it offers both a rationale for the relatively high hydrogen-atom-transfer reactivity of [Mn(O)(N4py)] and a guideline for creating more reactive complexes through ligand modification. Here we employ a combination of electronic absorption and variable-temperature magnetic circular dichroism (MCD) spectroscopy to experimentally evaluate this excited-state reactivity model. Using these spectroscopic methods, in conjunction with time-dependent density functional theory (TD-DFT) and complete-active space self-consistent-field calculations (CASSCF), we define the ligand-field and charge-transfer excited states of [Mn(O)(N4py)]. Through a graphical analysis of the signs of the experimental C-term MCD signals, we unambiguously assign a low-energy MCD feature of [Mn (O)(N4py)] as the E excited state predicted to be involved in hydrogen-atom-transfer reactivity. The CASSCF calculations predict enhanced Mn-oxyl character on the excited-state E surface, consistent with previous DFT calculations. Potential-energy surfaces, developed using the CASSCF methods, are used to determine how the energies and wave functions of the ground and excited states evolved as a function of Mn═O distance. The unique insights into ground- and excited-state electronic structure offered by these spectroscopic and computational studies are harmonized with a thermodynamic model of hydrogen-atom-transfer reactivity, which predicts a correlation between transition-state barriers and driving force. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2016 holdings: @attributes: islocal: N |
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