Silver indium diphosphate, AgInP2O7

Polycrystalline material of the title compound, AgInP2O7, was synthesized by traditional high-temperature solid-state methods and single crystals were grown from the melt of a mixture of AgInP2O7 and B2O3 as flux in a platinium crucible. The structure consists of InO6 octa­hedra, which are corner-shared to PO4 tetra­hedra into a three-dimensional network with hexa­gonal channels running parallel to the c axis. The silver cation, located in the channel, is bonded to seven O atoms of the [InP2O7] framework with Ag–O distances ranging from 2.370 (2) to 3.015 (2) Å. The P2O7 diphosphate anion is characterized by a P—O—P angle of 137.27 (9) and a nearly eclipsed conformation. AgInP2O7 is isotypic with the M IFeP2O7 (M I = Na, K, Rb, Cs and Ag) diphosphate family

Étude du spectre vibrationnel de groupements «pyro» de structure linéaire dans le pyrosilicate, le pyrogermanate et le pyrovanadate de Thallium monovalent

The vibrational spectra of Tl6Si2O7, Tl6Ge2O7 and Tl4V2O7 have been interpreted, the first two being isostructural and of known structure. The observed frequencies (40-1000 cm-1) have been separated in lattice modes and internal modes ; most of the normal modes of vibration of a X2O7 group (X = Si, Ge, V) with the D3h symmetry (highest symmetry for X2O7 with an eclipsed configuration) have been identified in the spectra. The symmetric stretching vibration of the X-O-X bridge is actif in Raman only whereas the corresponding antisymmetric mode is IR active. This is in agreement with a linear geometry for the X-O-X bridge in the three compounds.Nous avons interprété les spectres de vibration de Tl6Si2O7, Tl6Ge2O7 et Tl4V2O7, les deux premiers étant isostructuraux et de structure connue. Les fréquences observées (40-1000 cm-1) ont été séparées en modes de réseau et en modes internes ; la plupart des modes normaux de vibration d'un groupement X2O7 (X = Si, Ge, V) de symétrie D3, (symétrie maximale pour un X2O7 en configuration éclipsée) ont été identifiés dans les spectres. L'activité du mode de vibration de valence symétrique du pont X-O-X en Raman uniquement et du mode antisymétrique correspondant en IR est en accord avec une géométrie linéaire du pont X-O-X dans les trois composés.Gabelica-Robert Mélanie. Étude du spectre vibrationnel de groupements «pyro» de structure linéaire dans le pyrosilicate, le pyrogermanate et le pyrovanadate de Thallium monovalent. In: Bulletin de la Classe des sciences, tome 64, 1978. pp. 293-303

Spectre vibrationnel de la fresnoite (Ba2TiOSi2O7) et de ses composés isostructuraux

peer reviewedTwo new isostructural compounds with fresnoite, Sr2TiSi2O8 and Ba2TiGe2O8, have been synthesized and investigated by X-ray diffraction and vibrational spectroscopy. The infrared (IR) and Raman spectra of fresnoite and fresnoite-like pyrosilicates are discussed on the basis of a factor group analysis and with the help of 28-30Si and 46-50Ti isotopic shifts. The short Ti-O bond participates to the 900-800 cm-1 region of the spectrum. However, because of an important mixing with some Si-O stretching modes having the same symmetry properties, no frequency is specifically related to the stretching of this bond. An assignment is also proposed for the remaining Si-O stretching frequencies. The existence or absence of a correlation between short Ti-O distances and high vibrational frequencies is briefly discussed. © 1981 Springer-Verlag

Spectre infrarouge de pyrophosphates cristallins et vitreux : préservation du groupe pyrophosphate dans la structure vitreuse

peer reviewedTwo families of pyrophosphates, namely MIMIIIP2O7 and M2IMIIIP2O7 have been synthesized and investigated by IR spectroscopy, the emphasis being put on the anti-symmetric and symmetric frequencies of the P-O-P bridge. These bands are still present in the spectra of the glasses obtained by rapid quenching of the corresponding melts. This strongly suggests that, contrarily to expectations, the pyrophosphate group is essentially conserved in the glassy structure. This interpretation is supported by the investigation of glassy phases whose composition extend from meta- to ortho-phosphate. © 1982

Synthèse, diffraction des rayons X et étude vibrationnelle de silicates et germanates isostructuraux avec la kentrolite Pb2Mn2Si2O9

peer reviewedNew germanates Pb2MIII2Ge2O9 (MIII = Fe, Mn, Sc, In) and silicates Pb2MIIMIVSi2O9 (MII = Mg, Ni, Co, Cu for MIV = Sn; MII = Co, Ni for MIV = Ti) have been synthesized by solid state reaction. Their X-ray powder diagrams may be indexed in the orthorhombic system and show that these compounds are isostructural with kentrolite Pb2Mn2Si2O9. Doubts are expressed about the published structure of kentrolite and it is shown that some aspects of the structure should be re-examined. The I.R. and Raman spectra of these compounds are fairly complicated, and their discussion is restricted to the region of SiO or GeO stretching frequencies. These spectra show the existence of a pyro-silicate or -germanate group. The symmetric and antisymmetric frequencies of the SiOSi bridge have been identified with the help of 28Si30Si isotopic shifts. Their difference νas-νsym depends on the ionic radius of the cations, and points to a non-linear bridge of the pyrosilicate group. © 1979

Spectre vibrationnel des silicates et germanates de type akermanite

The i.r. and Raman spectra of A112B11X2O7 pyro-silicates and -germantes having the akermanite, or an akermanite-like, structure are reported and interpreted with the help of a group theoretical analysis, and 24Mg-26Mg and 28Si-30Si isotopic shifts. The stretching vibrations of the Si2O7 or Ge2O7 groups are generally free from interactions with the lattice frequencies whereas some of the bending vibrations of these groups are strongly mixed up with vibrations of the B11O4 tetrahedra. The existing data on the vibrations of these tetrahedral groups have been confirmed and extended. The XOX bridge frequencies of the pyro groups have been identified; the value of the bridge angle deduced from these frequencies is in satisfactory agreement with the literature values obtained by X-ray diffraction. © 1979

Investigation of non-covalent interactions between paramagnetic complexes and human serum albumin by electrospray mass spectrometry

Stable gadolinium(III) chelates are nowadays routinely used as contrast agents for magnetic resonance imaging (MRI). Their non-covalent binding to human serum albumin (HSA) has shown to improve their efficacy. Non-covalent interactions lead to complex formation that can be quantified by several techniques that are mostly tedious and time-consuming. In this study, electrospray ionization mass spectrometry (ESI-MS) was used to investigate the interaction between HSA and several gadolinium(III) complexes. The results were compared with those obtained in the liquid phase. Four gadolinium complexes were investigated: Gd-DTPA 1, Gd-C4Me-DTPA 2, Gd-EOB-DTPA 3, and MP-2269 4. Relaxometry studies show that complexes 1 and 2 have no significant affinity for HSA, while complexes 3 and 4 have increasing affinities for the protein. 1:1 and 1:2 complexes between HSA and MP-2269 were detected by ESI-MS for a twofold excess of the contrast agent, whereas a ligand/protein molar ratio of 4:1 was necessary to observe a 1:1 stoichiometry for Gd-EOB-DTPA, an observation that is in good agreement with the known weaker affinity of the contrast agent for the protein. At a fourfold molar excess, no supramolecular complex was observed for Gd-DTPA I and Gd-C4Me-DTPA 2; a tenfold molar excess was necessary to detect a 1:1 complex, confirming the very weak affinity of these contrast agents for HSA