The use of the TCNQF₄^2-dianion in the spontaneous redox formation of [Fe^III(L^-)₂][TCNQF₄•-]

The reaction of [FeII(L •)2](BF4)2 with Li2TCNQF4 results in the formation of [FeIII(L-)2][TCNQF4•-] (1) where L• is the radical ligand, 4,4-dimethyl-2,2-di(2-pyridyl)oxazolidine-N-oxide and TCNQF4 is 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyano-quinodimethane. This has been characterised by x-ray diffraction, Raman and Fourier-transform infra-red (FTIR) spectroscopy, variable temperature magnetic susceptibility, Mössbauer spectroscopy and electrochemistry. X-ray diffraction studies, magnetic susceptibility measurements and Raman and FTIR spectroscopy suggest the presence of low-spin FeIII ion, the anionic form (L-­) of the ligand and the anionic radical form of TCNQF4; TCNQF4•-. Li2TCNQF4 reduces the [FeII(L•)2]2+ dication which undergoes a reductively induced oxidation to form the [FeIII(L-)2]+ monocation resulting in the formation of [FeIII(L-)2][TCNQF4•-] (1), the electrochemistry of which revealed four well-separated, diffusion controlled, one-electron, reversible processes. Mössbauer spectroscopy and electrochemical measurements suggest the presence of a minor second species, likely to be [FeII(L•)2][TCNQF42-]

A purple acid phosphatase from sweet potato contains an antiferromagnetically coupled binuclear Fe-Mn center

A purple acid phosphatase from sweet potato is the first reported example of a protein containing an enzymatically active binuclear Fe-Mn center. Multifield saturation magnetization data over a temperature range of 2 to 200 K indicates that this center is strongly antiferromagnetically coupled. Metal ion analysis shows an excess of iron over manganese. Low temperature EPR spectra reveal only resonances characteristic of high spin Fe(III) centers (Fe(III)-apo and Fe(III)-Zn(II)) and adventitious Cu(II) centers. There were no resonances from either Mn(II) or binuclear Fe-Mn centers. Together with a comparison of spectral properties and sequence homologies between known purple acid phosphatases, the enzymatic and spectroscopic data strongly indicate the presence of catalytic Fe(III)-Mn(II) centers in the active site of the sweet potato enzyme. Because of the strong antiferromagnetism it is likely that the metal ions in the sweet potato enzyme are linked via a mu -oxo bridge, in contrast to other known purple acid phosphatases in which a mu -hydroxo bridge is present. Differences in metal ion composition and bridging may affect substrate specificities leading to the biological function of different purple acid phosphatases

Monocristaux semi-conducteurs derives de radicaux-cations phtalocyanines et naphtalocyanines de metaux 3d : structure, spectres et conductivite

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Crystal structure of [bis-tris(pyrazolyl)methanecobalt(II)] [chlorobis(eta(2)-benzoato)-eta1-benzoato-manganate(II)] hydrate, Co(C(10)H(10)N(6))Mn(C(7)H(5)O(2))(3)Cl (.) H(2)O

Zeitschrift fur Kristallographie - New Crystal Structures2183354-35

Crystal structure of bis(h1-benzoato)tris(1-pyrazolyl)methanecopper(II) hydrate, C24H22CuN6O5

Zeitschrift fur Kristallographie - New Crystal Structures2172219-22

Crystal structure of m2-oxo-bis-m2-formato-bis(tris(pyrazolyl)methane)diiron(III) perchlorate, C22H22Cl2Fe2N12O13

Abstract C11H11ClFeN6O6.50, orthorhombic, Pnnm (No. 58), a = 12.733(6) Å, b = 15.315(9) Å, c = 16.260(5) Å, V = 3170.8Å3, Z = 8, Rgt(F) = 0.058, wRref(F2) = 0.200, T = 293 K.</jats:p