OBSERVATION OF BIPHASIC KINETICS IN LIGHT-INDUCED SPIN-STATE CROSSOVER IN AN IRON(II) COMPLEX IN SOLUTION

Relaxation of the 1A1 half arrow right over half arrow left 5T2 spin equilibrium in acetonitrile of the complex of Fe(II) with the multidentate pyridyl macrocyclic ligand N,N',N''-tris(2-pyridylmethyl)-1,4,7-triazacyclodecane (tp[10]aneN3) after perturbation by a pulsed laser provides the first example of biphasic kinetics for spin crossover in solution with a fast (tau

UV VIS AND RESONANCE RAMAN SPECTROELECTROCHEMICAL PROPERTIES OF TRANSITION-METAL CENTERS IMMOBILIZED WITHIN A POLY(AMINO ACID) MATRIX - ILLUSTRATED WITH AN IRON PORPHYRIN

An iron prophyrin complex has been immobilized on the surfaces of platinum, silver, and indium doped-tin oxide coated glass by using the poly(gamma-ethyl L-glutamate)-N-(3-aminopropyl)imidazole derivative 1 as a linking agent, thus allowing-the surface-enhanced resonance Raman and UV-VIS absorption spectra and electrochemical properties of the porphyrin to be studied in solvents in which it is not normally soluble.

OXOIRON(IV) PORPHYRINS DERIVED FROM CHARGED IRON(III) TETRAARYLPORPHYRINS AND CHEMICAL OXIDANTS IN AQUEOUS AND METHANOLIC SOLUTIONS

The oxidation of six charged iron(III) tetraarylporphyrins with chemical oxidants has been investigated. In aqueous solution each can be converted by tert-butyl hydroperoxide or monopersulphate into its corresponding oxoiron(IV) porphyrin, whereas in methanol only the iron(III) tetra(N-methylpyridyl)porphyrins form detectable ferryl porphyrins at ambient temperatures. On standing, the iron species revert to the parent porphyrin with a small loss due to non-reversible oxidative destruction. That the oxidised porphyrin intermediates are oxoiron(IV) species has been determined using UV-VIS, resonance Raman, H1 NMR and EPR spectroscopy.

RESONANCE RAMAN INVESTIGATION OF PH-DEPENDENT EQUILIBRIA OF WATER-SOLUBLE IRON PORPHYRINS

Resonance Raman spectroscopy has been used to probe the structures of; tetrakis(1-methylpyridinium-4-yl)-porphinatoiron(III), FeIII (T4MPyP); tetrakis(1-methylpyridium-2-yl)porphinatoiron(III), FeIII (T2MPyP); tetrakis(4-sulphonatophkenyl)porphinatoir(III), FeIII(TSPP); and tetrakis(4-carboxylatophenyl)porphinatoiron(III), FeIII(TCPP), over a wide pH range. The anionic complexes FeIII (TSPP) and FeIII (TCPP) contain high-spin iron(III) at all pHs. Both these complexes exhibit marked spectral changes at ca. pH 6 which correspond to conversion from the diaquo species, in acid solution, to hydroxy- or mu-oxo dimer complexes. Both cationic complexes show similar diaquo to high-spin hydroxy, or mu-oxo dimer, transitions at ca. pH 6. However, at pH > 11.5 for FeIII (T4MPyP) and pH > 9 for FeIII (T2MPyP) a second equilibrium process is observed, leading to two new species. One of these is readily assigned as the low-spin iron(III) dihydroxy complex by analogy with spectra of the dicyano complex. The second species is assigned to the hydroxy iron(II) complex by comparison with photo-chemically generated FeII (T4MPyP) (OH). The formation of iron(II) species in alkaline solutions of FeIII (T4MPyP) and FeIII (T2MPyP) is entirely unexpected and the significance of the observation to previous investigations of the pH-dependent behaviour of these complexes is discussed.

Abatement of nitrous oxide over natural and iron modified natural zeolites

The natural zeolite obtained from the Sivas-Yavu region in Turkey and iron modified forms were studied for the decomposition of N2O and selective catalytic reduction of N2O with NH3. The natural and iron modified zeolites were characterised by XRD, SEM, H-2-TPR, NH3-TPD and low temperature nitrogen sorption. The effect iron loading, precursor and valency on the catalytic performance of catalysts were studied. The catalytic activity of the zeolites increased up to about 7.0 wt.% Fe. Above this value, the activity decreased as a result of a reduction in the surface area and pore volume of the zeolite. The highest catalytic activity was observed using catalysts prepared with FeCl2 due to the formation of more reducible iron species in the zeolites. When FeSO4 was used as the iron precursor, sulphate remained on the surface even after extensive washing resulting in a decrease in the N2O decomposition activity and a shift the N2O reduction temperature to higher values. Since the natural and iron exchanged natural zeolites prepared using FeCl2 have comparable activity with synthetic zeolites, the offer a promising alternative catalyst for the abatement of N2O, particularly for the selective reduction of N2O with NH3. (C) 2011 Elsevier B.V. All rights reserved.

Bovine Serum Albumin Adsorption to Iron-Oxide Coated Sands Can Change Microsphere Deposition Mechanisms

Particulate colloids often occur together with proteins in sewage-impacted water. Using Bovine Serum Albumin (BSA) as a surrogate for protein in sewage, column experiments investigating the capacity of iron-oxide coated sands to remove latex microspheres from water revealed that microsphere attenuation mechanisms depended on antecedent BSA coverage. Dual pulse experiment (DPE) results suggested that where all BSA was adsorbed, subsequent multiple pore volume microsphere breakthrough curves reflected progressively reduced colloid deposition rates with increasing adsorbed BSA content. Modelling colloid responses suggested adsorption of 1 µg BSA generated the same response as blockage by between 7.1x108 and 2.3x109 deposited microspheres. By contrast, microsphere responses in DPEs where BSA coverage of the deposition sites approached/ reached saturation revealed the coated sand maintained a finite capacity to attenuate microspheres, even when incapable of further BSA adsorption. Subsequent microsphere breakthrough curves demonstrated the matrix’s colloid attenuation capacity progressively increased with continued microsphere deposition. Experimental findings suggested BSA adsorption on the sand surface approaching/ reaching saturation generated attractive deposition sites for colloids, which became progressively more attractive with further colloid deposition (filter ripening). Results demonstrate that adsorption of a single type of protein may either enhance or inhibit colloid mobility in saturated porous media.