The magnetic susceptibilities, Móssbauer spectra, and electron paramagnetic resonance (EPR) spectra of [Fe(acen)-(dpp)](BPh4), [Fe(acen)(pic)2](BPh4), and [Fe(acen)(lut)2](BPh4) have been measured in the solid state [acen = N,-JV-bis(l-methyl-3-oxobutylidene)ethylenediamine, dpp = l,3-di-4-pyridylpropane, pic = 4-methylpyridine, lut = 3,4-dimethylpyridine, and BPh4 = tetraphenylborate ion]. The variable-temperature magnetic susceptibility for these complexes has been interpreted by the spin-crossover phenomenon between 6A and 2T states. The EPR parameters for the 2T state have been used to determine the energy levels of three Kramers doublets. The temperature dependence of the Móssbauer spectra for [Fe(acen)(dpp)](BPh4) and [Fe(acen)(pic)2](BPh4) has proved the existence of rapid electronic relaxation between two spin states in comparison with the Móssbauer lifetime of 0.97 X 10~7 s. The separation energies between the two spin states have been estimated to be 330 and 339 cm"1 for [Fe(acen)(dpp)](BPh4) and [Fe(acen)(pic)2](BPh4), respectively, by the theoretical calculation of the temperature dependence of the quadrupole splittings.
The Mössbauer emission spectra of [57Co(terpy)2]X2 (X=Cl and ClO4), [57Co(snn)2](ClO4)2, and [57Co(snnme)2](ClO4)2 (terpy=2,2′ : 6′2″-terpyridine, snn=N-(2-pyridylmethylene)-2-(methylthio)aniline, and snnme=N-(6-methyl-2-pyridylmethylene)-2-(methylthio)aniline) were examined. These cobalt complexes show thermally induced spin crossover behavior and the temperature dependence of their magnetic moment varies with the counter anion, although the corresponding iron complexes are in a low-spin state. The high-spin iron(II) species ascribed to a metastable form are observed in the emission spectra of [57Co(terpy)2](ClO4)2·2H2O and [57Co(snnme)2](ClO4)2, and their spectral areas increase with decreasing source temperature. The effective vibrating mass for the iron complex observed in the emission spectra of [57Co(snnme)2](ClO4)2 was calculated from the temperature dependence of the isomer shift value, and was used to distinguish whether the iron complex formed by EC-decay of a cobalt-57 atom is stable or metastable.
N,N′-Bis(1-methyl-3-oxobutylidene)ethylenediaminato-1,3-di-4-pyridylpropaneiron(III) tetraphenylborate was synthesized and the temperature dependences of the Mössbauer spectrum and magnetic susceptibility for the compound were measured. The fact that the electronic relaxation between 6A1 and 2T2 states is faster than the lifetime (0.86×10−7 s) of the nuclear excited state of an 57Fe Mössbauer atom was confirmed by means of Mössbauer spectroscopy.
Mössbauer and infrared spectroscopies have been applied to the study of the gamma-ray-irradiation effects on eleven iron 1,10-phenanthroline compounds: [Fe(phen)2X2] (X=Cl−, HCOO−, NCO−, 1⁄2Ox2−, 1⁄2Mal2−, CN−, and NO2−), [Fe(phen)3]X2·nH2O (X=Cl−, ClO4−, HCOO−, and NO2−), [Fe(phns)2](ClO4)2·2H2O and [Fe(phnc)2](ClO4)2·H2O (phen=1,10-phenanthroline, phns=1,10-phenantroline-2-carbothioamide, and phnc=1,10-phenantroline-2-carboxamide). For all the low-spin complexes except [Fe(phen)3] (HCOO)2·6H2O, no chemical changes were observed on the Mossbauer spectra after irradiation. All the iron(II) complexes in the high-spin state except [Fe(phen)2Cl2] and [Fe(phnc)2] (ClO4)2·H2O were, however, changed to iron(III) species under the influence of irradiation. Three iron(II) complexes in the intermediate-spin state were sensitive to gamma-rays.
New intercalated compounds of FeOCl and aniline derivatives were synthesized by soaking FeOCl in ethanol solution containing Lewis base intercalants. Only those Lewis base intercalants whose acid-dissociation constant is greater than 5 intercalate into the lattice of FeOCl. The acid-strength of the solvent is important for the formation of an intercalation compound. The intercalates of iron(III) chloride oxide FeOCl(G)1⁄n have been characterized by elemental analysis, powder pattern of X-ray diffraction, Fe-57 Mössbauer and infrared spectroscopies. The research on expansion of the b-axis of the unit cell and IR data confirm the location of the “guest” molecule within the van der Waals layer or the FeOCl lattice. Effective vibrating mass and lattice temperature derived from the Mossbauer spectra are affected by chemical bonding in the first coordination sphere of the iron atom.
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