A FeIII/Oxo Cubane Contained in an Octanuclear Complex of T Symmetry That Is Stable Over Five Oxidation States

Abstract

Thermodynamic stability is a desired property of materials prepared for commercial applications, but, at the same time, chemical versatility is required for the manifestation of interesting properties such as catalytic activity. A reconciliation of these opposite characteristics is typically achieved by the coating of large surfaces or particles with inert substances on a macroscopic and microscopic scale. Nature applies similar techniques at the macromolecular level when metal active centers are protected inside the organic part of metalloproteins. We propose that a molecular-level analogue of this principle, placing redox-active metal clusters in a chemically inert shell, will result in ideal building blocks for the construction of durable supercluster assemblies with electron transfer properties.Pyrazolates are convenient bridging ligands for the synthesis of polynuclear complexes in which, owing to the aromatic character of the ligand, the chemical activity is restricted to the metal centers.[1] Here we present the characterization and initial studies of [Fe 8 (m 4

Synthesis, Characterization, and Study of Octanuclear Iron-Oxo Clusters Containing a Redox-Active Fe4O4-Cubane Core

“…Noting also that many metalloproteins remain to be discovered, Lippard et al and we have suggested that an electron-transfer protein with a Fe 4 O 4 active center may be recognized in the future. 15,20 Continuing our studies of the octanuclear cluster 1, we report here the magnetic susceptibility, Density Functional Theory (DFT) study, infrared, Raman, 1 H-NMR and Mössbauer spectroscopic characterization of 1, along with the syntheses, structural characterization and electrochemical studies of its substituted-pyrazole derivatives, Fe 8 (μ 4 -O) 4 (μ-pz*) 12 Cl 4 , where pz* = 4-Cl-pz (2) and 4-Me-pz (3), along with the bromo-analogue, Fe 8 (μ 4 -O) 4 (μ-pz) 12 Br 4 , 4. These studies probe the electronic structure of the Fe 4 O 4 motif and define its spectroscopic and magnetic "fingerprint", facilitating its possible future recognition in Nature.…”

“…) consist of a Fe 4 O 4 -cubane encapsulated inside a shell of four Fe(pz*) 3 Cl units (the crystal structure of the hexane solvate of 1 has been previously communicated20 ). Bond lengths and angles for 1 -4 are summarized inTable 2.…”

First principles study of electronic structure for cubane-like and ring-shaped structures of M4O4, M4S4 clusters (M = Mn, Fe, Co, Ni, Cu)

“…22,23 Our aim, in this work, will be, therefore, to perform a rigorous relative structural stability analysis of each M 4 X 4 cluster between the two commonly found geometrical blocks, namely a 2D rhombus-like planar structure versus a 3D cubane-like structure. The special interest in these two structures, is mainly motivated by their relevance to multi-electron transfer centers in biological systems, 24,25 their interesting magnetic and optical properties, [26][27][28][29] as well as to their potential relevance to inorganic solids. 30 Many poly-nuclear complexes containing cubane-type M 4 O 4 /M 4 S 4 core units, have been studied extensively during the last decade.…”

Crystal structures and magnetic interactions in nickel(II) dibridged complexes formed by both phenolate oxygen-azide, or methanlate groups

“…Hetero-and homo-binuclear complexes of Ni(II) have attracted much attention over recent years due to their relevance to the active sites of metalloenzymes [1][2][3][4], and potential applications as optical [5,6], electronic, and molecule-based magnetic materials [7][8][9][10][11][12][13]. The structures of the products are dependent on many factors, such as the structure of chelating ligands [14][15][16], metal centers, anions, and solvents [17].…”