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

In this work, we report a new octanuclear cluster based on Fe III and the ligand 1 H -imidazole-4,5-dicarboxylic acid, [Et 3 NH] 12 [Fe 8 (IDC) 12 ]·10DMF·13H 2 O ( 1 ), with a metal core containing eight Fe III 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 {[Fe 8 (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 [Fe 8 (IDC) 12 ] 12- . Mössbauer spectra recorded at different temperatures show an isomer shift and quadrupole splitting parameters that confirm the existence of only Fe III -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 Fe III atoms located at the corners of the cube and connected by μ-1κ 2 N , O :2κ 2 N ', O ‴-IDC 3- bridges. Additionally, the magnetic measurements reveal a weak antiferromagnetic coupling in the Fe 8 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 1 H -imidazole-4,5-dicarboxylic acid and Fe III 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.