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The Nature of the Mn(III) Color Centers in Elbaite Tourmalines

Kurtz, Daniel A. and Rossman, George R. and Hunter, Bryan M. (2020) The Nature of the Mn(III) Color Centers in Elbaite Tourmalines. Inorganic Chemistry, 59 (14). pp. 9618-9626. ISSN 0020-1669. https://resolver.caltech.edu/CaltechAUTHORS:20200608-115356760

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Abstract

The characteristic red color of many natural tourmalines is due to the presence of Mn(III) cations substituting for aluminum and lithium. These sites originate as Mn(II) and are oxidized by natural γ-irradiation over geologic time as they sit in the Earth’s crust. Presented here is a thorough analysis of the spin-allowed and spin-forbidden transitions which give rise to the color of these gemstones. Ligand field analysis, supplemented by time-dependent density functional theory, was used to correct the historical assignments of the symmetry-allowed transitions in the polarized UV–visible absorption spectrum. Heat-induced reduction of the oxidized manganese sites provided a probe of the relationship between the spin-allowed and spin-forbidden bands. Notably, the intensity of the spin-forbidden transition was highly dependent on the neighboring ions in the Y-site. Simulations and modeling showed that increased intensity was observed only when two Mn(III) ions occupied adjacent substitutions in the Y-site via a proposed exchange-coupling mechanism.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/acs.inorgchem.0c00722DOIArticle
ORCID:
AuthorORCID
Kurtz, Daniel A.0000-0002-0082-1699
Rossman, George R.0000-0002-4571-6884
Hunter, Bryan M.0000-0001-8559-9304
Additional Information:© 2020 American Chemical Society. Received: March 9, 2020; Published: June 5, 2020. B.M.H. is a Fellow of the Rowland Institute at Harvard, which supported this work. Support for the instrumentation at Caltech was provided by NSF EAR-1322082 and the White Rose Foundation to G.R.R. B.M.H. gratefully acknowledges David Hammett for helpful mathematical discussions. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
Rowland InstituteUNSPECIFIED
NSFEAR-1322082
White Rose FoundationUNSPECIFIED
Issue or Number:14
Record Number:CaltechAUTHORS:20200608-115356760
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200608-115356760
Official Citation:The Nature of the Mn(III) Color Centers in Elbaite Tourmalines. Daniel A. Kurtz, George R. Rossman, and Bryan M. Hunter. Inorganic Chemistry 2020 59 (14), 9618-9626; DOI: 10.1021/acs.inorgchem.0c00722
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103772
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:08 Jun 2020 21:22
Last Modified:31 Jul 2020 16:25

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