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Severa G, Bruffey E, Nguyen PQH, Gigante A, Leick N, Kelly C, Finkelstein GJ, Hagemann H, Gennett T, Rocheleau RE, Dera P. Fe 4(OAc) 10[EMIM] 2: Novel Iron-Based Acetate EMIM Ionic Compound. ACS OMEGA 2021; 6:31907-31918. [PMID: 34870013 PMCID: PMC8637965 DOI: 10.1021/acsomega.1c04670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/25/2021] [Indexed: 06/13/2023]
Abstract
We synthesized and characterized a novel iron(II) aceto EMIM coordination compound, which has a simplified empirical formula Fe4(OAc)10[EMIM]2, in two different hydration forms: as anhydrous monoclinic compound and triclinic dihydrate Fe4(OAc)10[EMIM]2·2H2O. The dihydrate compound is isostructural with recently reported Mn4(OAc)10[EMIM]2·2H2O, while the anhydrate is a superstructure of the Mn counterpart, suggesting the existence of solid solutions. Both new Fe compounds contain chains of Fe2+ octahedrally coordinated exclusively by acetate groups. The EMIM moieties do not interact directly with the Fe2+ and contribute to the structural framework of the compound through van der Waals forces and C-H···O hydrogen bonds with the acetate anions. The compounds have a melting temperature of ∼94 °C; therefore, they can be considered metal-containing ionic liquids. Differential thermal analysis indicates three endothermic transitions associated with melting, structural rearrangement in the molten state at about 157 °C, and finally, thermal decomposition of the Fe4(OAc)10[EMIM]2. Thermogravimetric analyses indicate an ∼72 wt % mass loss during the decomposition at 280-325 °C. The Fe4(OAc)10[EMIM]2 compounds have higher thermal stability than their Mn counterparts and [EMIM][OAc] but lower compared to iron(II) acetate. Temperature-programmed desorption coupled with mass spectrometry shows that the decomposition pathway of the Fe4(OAc)10[EMIM]2 involves four distinct regimes with peak temperatures at 88, 200, 267, and 345 °C. The main species observed in the decomposition of the compound are CH3, H2O, N2, CO, OC-CH3, OH-CO, H3C-CO-CH3, and H3C-O-CO-CH3. Variable-temperature infrared vibrational spectroscopy indicates that the phase transition at 160-180 °C is associated with a reorientation of the acetate ions, which may lead to a lower interaction with the [EMIM]+ before the decomposition of the Fe4(OAc)10[EMIM]2 upon further heating. The Fe4(OAc)10[EMIM]2 compounds are porous, plausibly capable of accommodating other types of molecules.
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Affiliation(s)
- Godwin Severa
- Hawai’i
Natural Energy Institute, University of
Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
| | - Edward Bruffey
- Hawai’i
Natural Energy Institute, University of
Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
| | - Phuong Q. H. Nguyen
- Hawai’i
Institute of Geophysics and Planetology, University of Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
| | - Angelina Gigante
- Département
de Chimie Physique, Université de
Genève, 30, quai E. Ansermet, 1211 Geneva 4, Switzerland
| | - Noemi Leick
- National
Renewable Energy Laboratory (NREL), Colorado, Colorado 80401, United States
| | - Colleen Kelly
- Hawai’i
Natural Energy Institute, University of
Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
| | - Gregory J. Finkelstein
- Hawai’i
Institute of Geophysics and Planetology, University of Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
| | - Hans Hagemann
- Département
de Chimie Physique, Université de
Genève, 30, quai E. Ansermet, 1211 Geneva 4, Switzerland
| | - Thomas Gennett
- National
Renewable Energy Laboratory (NREL), Colorado, Colorado 80401, United States
- Chemistry
Department, Colorado School of Mines, 1012 14th Street, Golden, Colorado 80401, United States
| | - Richard E. Rocheleau
- Hawai’i
Natural Energy Institute, University of
Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
| | - Przemyslaw Dera
- Hawai’i
Institute of Geophysics and Planetology, University of Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
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