Title: Fe ₄ (OAc) ₁₀ [EMIM] ₂ : Novel Iron-Based Acetate EMIM Ionic Compound

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 peakmore » 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.« less

Authors:

Severa, Godwin  ^[1];

• Search DOE PAGES for author "Severa, Godwin"
• Search DOE PAGES for ORCID "0000-0002-1695-9123"
• Search orcid.org for ORCID "0000-0002-1695-9123"

Bruffey, Edward ^[1]; Nguyen, Phuong Q. H. ^[2]; Gigante, Angelina  ^[3];

• Search DOE PAGES for author "Gigante, Angelina"
• Search DOE PAGES for ORCID "0000-0002-7226-1360"
• Search orcid.org for ORCID "0000-0002-7226-1360"

Leick, Noemi  ^[4];

• Search DOE PAGES for author "Leick, Noemi"
• Search DOE PAGES for ORCID "0000-0002-2014-6264"
• Search orcid.org for ORCID "0000-0002-2014-6264"

Kelly, Colleen ^[1]; Finkelstein, Gregory J. ^[2]; Hagemann, Hans  ^[3];

• Search DOE PAGES for author "Hagemann, Hans"
• Search DOE PAGES for ORCID "0000-0002-7183-8543"
• Search orcid.org for ORCID "0000-0002-7183-8543"

Gennett, Thomas ^[5]; Rocheleau, Richard E. ^[1]; Dera, Przemyslaw ^[2]

---

+ Show Author Affiliations

1. Hawai’i Natural Energy Institute, University of Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
2. Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Ma̅noa, 1680 East West Road, POST 109, Honolulu, Hawaii 96822, United States
3. Département de Chimie Physique, Université de Genève, 30, quai E. Ansermet, 1211 Geneva 4, Switzerland
4. National Renewable Energy Laboratory (NREL), Colorado, Colorado 80401, United States
5. National Renewable Energy Laboratory (NREL), Colorado, Colorado 80401, United States, Chemistry Department, Colorado School of Mines, 1012 14th Street, Golden, Colorado 80401, United States

Publication Date:

2021-11-16

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Hawaii at Manoa, Honolulu, HI (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office; US Office of Naval Research (ONR)

OSTI Identifier:

1830431

Alternate Identifier(s):

OSTI ID: 1832859; OSTI ID: 1833336

Report Number(s):

NREL/JA-5900-79494
Journal ID: ISSN 2470-1343

Grant/Contract Number:  

AC36-08GO28308; N00014-15-1-0028; N00014-17-1-2206

Resource Type:

Published Article

Journal Name:

ACS Omega

Additional Journal Information:

Journal Name: ACS Omega Journal Volume: 6 Journal Issue: 47; Journal ID: ISSN 2470-1343

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Gas sorption; Iron containing ionic liquid; Salts; Organic reactions; Solvents; Organic compounds; Transition metals