Preparation and physical properties of oxidation products of oxo-bridged binuclear iron(III) complexes. Mixed-valence diiron(III, IV) complexes

Benzene-1,4-Di(dithiocarboxylate) Linker-Based Coordination Polymers of Mn2+, Zn2+, and Mixed-Valence Fe2+/3

Three new coordination polymers (CPs) constructed from the linker 1,4-di(dithiocarboxylate) (BDDTC2-)─the sulfur-analog of 1,4-benzenedicarboxylate (BDC2-)─together with Mn-, Zn-, and Fe-based inorganic SBUs are reported with description of their structural and electronic properties. Single-crystal X-ray diffraction revealed structural diversity ranging from one-dimensional chains in [Mn(BDDTC)(DMF)2] (1) to two-dimensional (2D) honeycomb sheets observed for [Zn2(BDDTC)3][Zn(DMF)5(H2O)] (2). Gas adsorption experiments confirmed a 3D porous structure for the mixed-valent material [Fe2(BDDTC)2(OH)] (3). 3 contains a 1:1 ratio of Fe2+/3+ ions, as evidenced by 57Fe Mössbauer, X-band EPR, and X-ray absorption spectroscopy. Its empirical formula was established by elemental analysis, thermal gravimetric analysis, infrared vibrational spectroscopy, and X-ray absorption spectroscopy in lieu of elusive single-crystal X-ray diffraction data. In contrast to the Mn- and Zn-based compounds 1 and 2, the Fe2+/3+ CP 3 showed remarkably high electrical conductivity of 5 × 10-3 S cm-1 (according to van der Pauw measurements), which is within the range of semiconducting materials. Overall, our study confirms that sulfur derivatives of typical carboxylate linkers (e.g., BDC) are suitable for the construction of electrically conducting CPs, due to acceptedly higher covalency in metal-ligand bonding compared to the electrically insulating carboxylate CPs or metal-organic frameworks. At the same time, the direct comparison between insulating CPs 1 and 2 with CP 3 emphasizes that the electronic structure of the metal is likewise a crucial aspect to construct electrically conductive materials.

Amorphous Fe(OH)3 Passivating CeO2 Nanorods: A Noble-Metal-Free Photocatalyst for Water Oxidation

Noble-metal-free composites with good photocatalytic property are of great interest. Here, CeO₂ nanorods composites loaded with amorphous Fe(OH)₃ cocatalyst were designed and prepared via a secondary water bath at 100 °C. The as-synthesized CeO₂ /amorphous Fe(OH)₃ composites exhibited superior light photocatalytic activities compared to pure CeO₂ , especially the sample with a loading time of 60 min. The photocatalytic oxygen generation rate could reach to 357.2 μmol h^-1  g^-1 , and the average apparent quantum yield (AQY) was 24.67 %, which was a 5.5-fold increase compared to the CeO₂ sample. The improvement of photocatalytic performance could be ascribed to three main reasons: First, loading the amorphous Fe(OH)₃ enlarged the specific surface area and passivated the surface of the pristine CeO₂ . Second, the amorphous Fe(OH)₃ ,which acted as a cocatalyst, provided many active sites, and reduced the reaction activation energy. Thirdly, the maximum interface with intimate contact between CeO₂ and amorphous Fe(OH)₃ cocatalyst accelerated the photogenerated charge separation efficiency and thus improved the photocatalytic performance of CeO₂ in photocatalytic water oxidation.

A novel enhanced anaerobic biodegradation method using biochar and Fe(OH)3@biochar for the removal of nitrogen heterocyclic compounds from coal gasification wastewater

Three identical lab-scale sequencing batch reactors (SBR) were operated for 120 days for raw (R₁), biochar (R₂), and Fe(OH)₃@biochar (R₃) enhanced anaerobic degradation of selected nitrogen heterocyclic compounds (NHCs). The occurrence of Fe-OH ensured the successful attachment of Fe(OH)₃ to biochar as evidenced by the Fourier transform infrared (FTIR) spectra of biochar and Fe(OH)₃@biochar. Acute biotoxicity experiments revealed that enhancing biochar and Fe(OH)₃@biochar effectively decreased the toxicity of microorganisms. Additionally, the introduction of biochar and Fe(OH)₃@biochar improved the settling performance of anaerobic sludge. Further, it was concluded that enriched Longilinea and Comamonas might be the major genera that function to degrade selected NHCs in anaerobic conditions.

Organic-inorganic hybrid materials based on iron(III)-polyoxotungstates and 1-butyl-3-methylimidazolium cations

The iron(III) μ-oxo bridged dimeric polyoxometalate [(PW(11)O(39)Fe)(2)O](10-) was isolated by reacting the transition metal monosubstituted Keggin anion [PW(11)O(39)Fe(H(2)O)](4-) and the ionic liquid 1-butyl-3-methylimidazolium bromide, (Bmim)Br, at pH 5.5. The crystal structure of (Bmim)(10)[(PW(11)O(39)Fe)(2)O]·0.5H(2)O (1) (monoclinic, space group P2(1)/n, Z = 4) was determined by single crystal X-ray diffraction. By changing the reaction conditions, (Bmim)(4)[PW(11)O(39)Fe(H(2)O)]·H(2)O (2) was obtained, whilst the reaction between the Bmim(+) cation and the heteropolyanion [SiW(11)O(39)Fe(H(2)O](5-), in the pH conditions used for 1, afforded (Bmim)(5)[SiW(11)O(39)Fe(H(2)O)]·4H(2)O (3). The compounds were characterized by spectroscopic techniques, thermal analysis, cyclic voltammetry, magnetic measurements and mass spectrometry. This study contributes to the understanding of iron μ-oxo dimer formation in polyoxometalate chemistry and calls attention to the influence of the counter-cations on the stability and formation of compound 1. The combination of the cationic part of ionic liquids and iron-substituted polyoxotungstates is predicted to lead to new materials with interest to catalysis, electrocatalysis and ionic liquid based nanocomposites.

A new one-pot synthesis of μ-oxo dimeric iron(III) porphyrins from meso-tetraarylporphyrins

A new synthesis of μ-oxo dimeric iron(III) porphyrins from meso-tetraarylporphyrins in one-pot procedure is reported. μ-oxo dimeric iron(III) porphyrin was obtained in high yield (up to 93%) from the reaction of meso-tetraarylporphyrin with ferrous chloride in DMF at pH 8–11. Compared with other synthetic methods of μ-oxo dimeric iron(III) porphyrin from meso-tetraarylporphyrins, the one-pot procedure has higher yields of μ-oxo dimeric iron(III) porphyrins and is a simpler and more convenient procedure. In order to evaluate the range of applicability of this method, μ-oxo dimeric iron(III) porphyrins with different substituents were prepared by the reaction of the corresponding meso-tetraarylporphyrins with ferrous chloride. The results showed that it was possible to apply this one-pot procedure to the synthesis of other μ-oxo dimeric iron porphyrins in excellent yields. A mechanism for the formation of μ-oxo dimeric iron porphyrins was proposed based on the reaction intermediates characterized by HPLC and UV-vis methods.

Nuclease Activity of Oxo-bridged Diiron Complexes

The dinuclear oxo-bridged complexes [Fe(salen)]2O, [Fe(salen)]2O - X (where X = pyridine, perchlorate) cleave plasmid pBR322 DNA in concert with H2O2.

Mixed valence state in ironporphyrin aggregates

In biological systems, metalloporphyrins play a central role in energy and electron transfer process. Our aim is to understand the influence of ligands and iron coordination of ironporphyrin on the electron transfer. The lyophilized ironporphyrin, enriched in 57Fe up to 90% has been studied by Mössbauer spectroscopy between 2.8 and 313 K. Above room temperature the bounded diffusion of the ferric iron was observed. Below 293 K a part of iron appears in mixed Fe+3<==>Fe+2 valence state with 10 meV activation energy for the electron trapping. Below 4 K a part of iron shows magnetic ordering with a broad distribution of the hyperfine field. The results are discussed in terms of metalloporphyrin aggregation process.