New Highly Charged Iron(III) Metal–Organic Cube Stabilized by a Bulky Amine

• Published in: ACS omega 2020-09, Vol.5 (35), p.22238-22247
• Main Authors: Cruz, Carlos, Vega Carvallo, Andrés Igor, Spodine, Evgenia, Escuer, Albert, Marco, José F, Menéndez, Nieves, Venegas-Yazigi, Diego, Paredes-García, Verónica
• Format: Article
• Language: English
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.0c02420

In this work, we report a new octanuclear cluster based on FeIII and the ligand 1H-imidazole-4,5-dicarboxylic acid, [Et3NH]12[Fe8(IDC)12]·10DMF·13H2O (1), with a metal core containing eight FeIII connected by only one type of organic ligand. A peak at 573 m/z in the mass spectra of the compound suggests the adduct species {[Fe8(IDC)12]+8H}4–. By X-ray photoelectron spectroscopy, the oxidation state of the iron cation was confirmed to be 3+, also identifying the presence of a quaternary nitrogen species, which act as a countercation of the anionic metal core [Fe8(IDC)12]12–. Mössbauer spectra recorded at different temperatures show an isomer shift and quadrupole splitting parameters that confirm the existence of only FeIII-HS in the structure of 1. X-ray analysis reveals that compound 1 crystallizes in the orthorhombic system space group Ibam, confirming a molecular cluster structure with an almost regular cube as geometry, with the FeIII atoms located at the corners of the cube and connected by μ-1κ2 N,O:2κ2 N′,O‴-IDC3– bridges. Additionally, the magnetic measurements reveal a weak antiferromagnetic coupling in the Fe8 III coordination cluster (J = −3.8 cm–1). To the best of our knowledge, 1 is the first member of the family of cubes assembled with 1H-imidazole-4,5-dicarboxylic acid and FeIII cation, exhibiting high pH stability over a broad pH range, making it an ideal candidate for the design of supramolecular structures and metal–organic frameworks.