X-ray absorption spectroscopy study of novel inorganic-organic hybrid ferromagnetic Cu-pyz-[M(CN)8]3- assemblies.

We present a unique interpretation of X-ray absorption spectroscopy (XAS) spectra at Cu:K, W:L(3), and Mo:K edges of structurally related magnetic Cu(II)-[M(V)(CN)(8)](3-) compounds. The approach results in description of the structure of novel three-dimensional (3-D) Cu(II)(3)(pyz)[M(V)(CN)(8)](2)·xH(2)O, M = W (1), Mo, (2) polymers. Assemblies 1 and 2 represent hybrid inorganic-organic compounds built of {Cu(II)[W(V)(CN)(8)](-)}(n) double-layers linked by cyanido-bridged {Cu(II)-(µ-pyz)(2+)}(n) chains. These Cu(II)-M(V) systems reveal long-range magnetic ordering with T(c) of 43 and 37 K for 1 and 2, respectively. The presence of the 3-D coordination networks and 8 cyanido-bridges at M(V) centers leads to the highest Curie temperatures and widest hysteresis loops among Cu(II)-[M(V)(CN)(8)](3-) systems.

X-ray absorption near edge structure and extended X-ray absorption fine structure analysis of Fe(II) aqueous and acetone solutions.

X-ray absorption spectroscopy measurements were used to determine the structure of the first coordination shell of Fe(II) ions in aqueous and acetone based solutions. Extended X-ray absorption fine structure analysis coupled with ab initio X-ray absorption near edge structure calculations confirms the octahedral coordination of the iron ion in water based solution. Data collected for acetone rich solutions can be reproduced assuming coexistence of the octahedral Fe(H(2)O)(6)(2+) and tetrahedral [FeCl(4)](2-) complexes. Distortion of the tetrahedral coordination of ion was detected in some of the acetone based solutions.

Structure of Te-rich Te-Ge-X (X = I, Se, Ga) glasses.

The structure of glassy Te(78)Ge(11)Ga(11), Te(79)Ge(16)Ga(5), Te(70)Ge(20)Se(10) and Te(73)Ge(20)I(7)--promising materials for far infrared applications--was investigated by means of x-ray and neutron diffraction as well as extended x-ray absorption fine structure measurements at various edges. Experimental data sets were fitted simultaneously in the framework of the reverse Monte Carlo simulation technique. Short range order in Te(85)Ge(15) was reinvestigated by fitting a new x-ray diffraction measurement together with available neutron diffraction and extended x-ray absorption fine structure data. It was found that Te(85)Ge(15) consists mostly of GeTe(4) structural units linked together directly or via bridging Te atoms. Te is predominantly twofold coordinated in Te(85)Ge(15), Te(70)Ge(20)Se(10) and Te(73)Ge(20)I(7) while in Te(78)Ge(11)Ga(11) and Te(79)Ge(16)Ga(5) the Te coordination number is significantly higher than 2. The Te-Te bond length is 2.80 ± 0.02 Å in Te(78)Ge(11)Ga(11) while it is as short as 2.70 ± 0.02 Å and 2.73 ± 0.02 Å in Te(73)Ge(20)I(7) and Te(70)Ge(20)Se(10), respectively. Our results show that the strengths of GeTe(4) (GeTe(3)I, GeTe(3)Se) 'units' are very similar in all glasses investigated but the connection between these units depends on the third component. Differences in the Te coordination number suggest that unlike Se or I, Ga does not build into the Ge-Te covalent network. Instead, it forms a covalent bond with the non-bonding p electrons of Te, which results in an increase in the average Te coordination number.