Structure and properties of bis(1-phenyl-1h-tetrazole-5-thiolate)diiron tetranitrosylстатья
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Аннотация:New tetranitrosyl binuclear iron complex [Fe-2(SC7H5N4)(2)(NO)(4)] (I) has been synthesized by interaction of aqueous solutions of anionic salts [Fe(S2O3)(2)(NO)(2)](3-) and [SC7H5N4](-). The latter one was synthesized by reduction of bis-(1-phenyl-1H-tetrazole-5-y1) disulfide with hydrazine hydrate in ethanol at T= 25 degrees C. Molecular and crystalline structure of I was determined by X-ray analysis; the complex has binuclear structure of "mu-SCN" type with similar to 4.02 angstrom between the iron atoms. Shortened O center dot center dot center dot O contacts (2.81 angstrom) between the NO groups of similar type are observed. Parameters of M6ssbauer spectrum for I are: isomer shift delta(Fe) = 0.311(1) mm/s, quadrupole splitting Delta E-Q = 1.044(1) mm/s, line width Gamma = 0.267(1) mm/s at 85 K. From SQUID magnetometry data, the temperature and field dependences of the magnetic moment of I are well described in the frame of a simple model of binuclear iron complex with magnetic centers S-1 = S-2 = 1/2. In solution, binuclear structure of the complex remains, though the NO groups are non-equivalent. For solutions of I five-line hyperfine structure of spectrum (HFS) is observed, g-factor = 2.03. For polycrystals of!, no HFS was observed due to averaged exchange interaction between the electron spins of adjacent complexes. In polycrystals of I, the number of spins per one binuclear complex is <2, this being the evidence of antiferromagnetic exchange interaction of unpaired electrons of two iron atoms. The average number of spins in crystals (0.65) and solutions (0.55) are close. The maximum amount of NO generated by 1 in 1% dimethylsulfoxide (DMSO) aqueous solution is similar to 13.8 nM, it halves in 8 min after decomposition starts, and reaches similar to 3.8 nM in anaerobic conditions at T=25 degrees C, pH 7.0. This is due, according to quantum-chemical calculations, to the presence of a more stable Fe-NO bond in I than in its isostructural analog - nitrosyl iron complex with 1-methyltetrazole-5-yl (II). (C) 2013 Elsevier B.V. All rights reserved.