Synthesis, Characterization, and Crystal Structures of Two New Manganese Aceto EMIM Ionic Compounds with Chains of Mn2+ Ions Coordinated Exclusively by Acetate

Przemyslaw Dera; Edward Bruffey 3rd; Gregory J Finkelstein; Colleen Kelly; Angelina Gigante; Hans Hagemann; Godwin Severa

doi:10.1021/acsomega.0c01820

Synthesis, Characterization, and Crystal Structures of Two New Manganese Aceto EMIM Ionic Compounds with Chains of Mn²⁺ Ions Coordinated Exclusively by Acetate

ACS Omega. 2020 Jun 18;5(25):15592-15600. doi: 10.1021/acsomega.0c01820. eCollection 2020 Jun 30.

Authors

Przemyslaw Dera¹, Edward Bruffey 3rd², Gregory J Finkelstein¹, Colleen Kelly², Angelina Gigante³, Hans Hagemann³, Godwin Severa²

Affiliations

¹ Hawai'i Institute of Geophysics and Planetology, University of Hawai'i at Ma̅noa, 1680 East West Rd, POST 109, Honolulu, Hawai'i 96822, United States.
² Hawai'i Natural Energy Institute, University of Hawai'i at Ma̅noa, 1680 East West Rd, POST 109, Honolulu, Hawai'i 96822, United States.
³ Département de Chimie Physique, Université de Genève, 30, Quai E. Ansermet, 1211 Geneva 4, Switzerland.

Abstract

We synthesized and determined crystal structures of two manganese(II) aceto EMIM coordination compounds with simplified empirical formulas Mn₄(OAc)₁₀[EMIM]₂ and Mn₄(OAc)₁₀[EMIM]₂·2H₂O. Both compounds feature extended chains of Mn²⁺ octahedrally coordinated exclusively by acetate anions, which has been observed for the first time. The EMIM moieties and water molecules participate in hydrogen bonding with acetate anions but do not directly interact with the metal cation. Both compounds have melting temperatures around 120 °C and can be considered as (non-room-temperature) ionic liquids. The structural arrangement represented by the two title compounds is robust in terms of accommodating other types of cations and allows for tuning of physical properties of the ionic liquid by means of cation substitution. Thermal analysis results obtained using TGA-DSC and VT IR suggest melting phase transitions around 120 °C, followed by structural rearrangement in the molten state taking place around 140-160 °C. Compounds I and II have a higher thermal stability range compared to [EMIM][OAc] ionic liquid, with an onset decomposition temperature above 260 °C.