Tetra-MnIII-Containing 30-Tungsto-4-phosphate, [MnIII4(H2O)2(P2W15O56)2]12-: Synthesis, Structure, XPS, Magnetism, and Electrochemical Study

Joydeb Goura; Manjiri Choudhari; Talha Nisar; Torsten Balster; Jasleen K Bindra; Jared Kinyon; Bushra Ali; Timothy McCormac; Naresh S Dalal; Veit Wagner; Ulrich Kortz

doi:10.1021/acs.inorgchem.0c01231

Tetra-Mn^III-Containing 30-Tungsto-4-phosphate, [Mn^III₄(H₂O)₂(P₂W₁₅O₅₆)₂]^12-: Synthesis, Structure, XPS, Magnetism, and Electrochemical Study

Inorg Chem. 2020 Sep 21;59(18):13034-13041. doi: 10.1021/acs.inorgchem.0c01231. Epub 2020 Aug 21.

Authors

Affiliations

¹ Department of Life Sciences and Chemistry, Jacobs University, Campus Ring 1, 28759 Bremen, Germany.
² Department of Physics and Earth Sciences, Jacobs University, Campus Ring 1, 28759 Bremen, Germany.
³ Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.
⁴ Dundalk Institute of Technology, Dundalk, County Louth, A91 K584, Ireland.

PMID: 32822165
DOI: 10.1021/acs.inorgchem.0c01231

Abstract

Reaction of the mixed-valent Mn₁₂-acetato complex [Mn^III₈Mn^IV₄O₁₂(CH₃COO)₁₆(H₂O)₄] with the trilacunary Wells-Dawson-type heteropolytungstate [P₂W₁₅O₅₆]^12- in acidic acetate solution (pH 1.1) resulted in the tetra-Mn^III-containing polyanion [Mn^III₄(H₂O)₂(P₂W₁₅O₅₆)₂]^12- (1). Single-crystal XRD on Na₁₂[Mn^III₄(H₂O)₂(P₂W₁₅O₅₆)₂]·84H₂O (1a) revealed that four Mn^III ions form a rhombic Mn₄O₁₆ core encapsulated by two [P₂W₁₅O₅₆]^12- units. X-ray photoelectron spectroscopy (XPS) data confirm the +3 oxidation state of the four manganese ions in 1. Magnetic measurements from 1.8-300 K in a 100 Oe magnetic field allowed for the extraction of full fitting parameters from the susceptibility data for 1. The negative J_a value (J_a = -2.16 ± 0.08 K, J_b = 3.24 ± 1.73 K, g = 2.35 ± 0.040, and ρ = 0.34 ± 0.03) suggests a dominant antiferromagnetic spin exchange interaction between the four Mn^III ions, with the positive J_b being an accompanying result of J_a. Electrochemical studies revealed a reversible Mn^IV/Mn^III redox couple in 1 at the +0.80 to +1.1 V potential region with E_1/2 = +0.907 V.