Recent developments of phosphate glasses for a variety of technological applications, from rare-earth ion hosts for solid state lasers to low temperature sealing glasses, have led to renewed interest in understanding the structures of these unusual materials. In this review, spectroscopic and diffraction studies of simple phosphate glasses, including v-P2O5 and binary phosphate compositions, are described. Special attention is given to the structures of anhydrous ultraphosphate glasses, which have received close attention from the glass community only in the past six years.

Review: the structure of simple phosphate glasses

http://projects.itn.pt/HeterNetworks_SRabaca/Coordination_Chemistry_Reviews_227_2002_93_127.pdf

Metal bis-1,2-dithiolene complexes in conducting or magnetic crystalline assemblies

The three diamagnetic square planar complexes of nickel(II), palladium(II), and platinum(II) containing two S,S-coordinated 3,5-di-tert-butylbenzene-1,2-dithiolate ligands, (L(Bu))(2-), namely [M(II)(L(Bu))(2)](2-), have been synthesized. The corresponding paramagnetic monoanions [M(II)(L(Bu))(L(Bu)(*))](-) (S = (1)/(2)) and the neutral diamagnetic species [M(II)(L(Bu)(*))(2)] (M = Ni, Pd, Pt) have also been generated in solution or in the solid state as [N(n-Bu)(4)][M(II)(L(Bu))(L(Bu)(*))] salts. The corresponding complex [Cu(III)(L(Bu))(2)](-) has also been investigated. The complexes have been studied by UV-vis, IR, and EPR spectroscopy and by X-ray crystallography; their electro- and magnetochemistry is reported. The electron-transfer series [M(L(Bu))(2)](2-,-,0) is shown to be ligand based involving formally one (L(Bu)(*))(-) pi radical in the monoanion or two in the neutral species [M(II)(L(Bu)(*))(2)] (M = Ni, Pd, Pt). Geometry optimizations using all-electron density functional theory with scalar relativistic corrections at the second-order Douglas-Kroll-Hess (DKH2) and zeroth-order regular approximation (ZORA) levels result in excellent agreement with the experimentally determined structures and electronic spectra. For the three neutral species a detailed analysis of the orbital structures reveals that the species may best be described as containing two strongly antiferromagnetically interacting ligand radicals. Furthermore, multiconfigurational ab initio calculations using the spectroscopy oriented configuration interaction (SORCI) approach including the ZORA correction were carried out. The calculations predict the position of the intervalence charge-transfer band well. Chemical trends in the diradical characters deduced from the multiconfigurational singlet ground-state wave function along a series of metals and ligands were discussed.

Electronic structure of square planar bis(benzene-1,2-dithiolato)metal complexes [M(L)(2)](z) (z = 2-, 1-, 0; M = Ni, Pd, Pt, Cu, Au): an experimental, density functional, and correlated ab initio study.

The chemistry and solid state properties of nickel, palladium and platinum bis(maleonitriledithiolate) compounds

The addition of up to ∼16 mol% Cs2O to vitreous P2O5 reduces the glass transition temperature (Tg) by 150 K, whereas further additions up to 60 mol% increases Tg by ∼20 K. 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra indicate that the phosphate network is progressively depolymerized over the entire range of compositions. The property trend is explained by a transition in the Cs+ coordination environment, from isolated Cs-polyhedra below ∼16 mol% Cs2O to a corner-sharing Cs-polyhedral sub-structure in the glasses with greater Cs2O contents. This ‘modifier transition’ does not occur in Al phosphate glasses. 27Al MAS NMR spectra indicate that the average Al coordination number decreases with increasing Al2O3 content to avoid the formation of Al–O–Al bonds in these binary phosphate glasses.

/pdf/modifier-coordination-and-phosphate-glass-networks-334ekuoosx.pdf

Modifier Coordination and Phosphate Glass Networks

An X-ray RDF study of Li2O_P2O5_LiCl glasses

The crystal and molecular structure of the title compound, (C13H11N2)[Ni(S2C6H4)2], is reported. Crystals are triclinic, space groupP¯1(No.2) withZ=2 in a unit cell of dimensionsa=9.363(1),b=10.148(1),c=13.623(1) A,α=85.64(1),β=107.33(1), and γ=113.10(1)°. The structure was solved by the heavy-atom method and refined by the method of full-matrix least squares toR=0.036 for 2874 unique reflections. The metal atom of the anion has an approximate square-planar configuration. The metal atoms occupy the origins and A-face centers of the lattice. The anions with the metal atoms in the origins stack along thec-axis, the interplanar separation being thec-axis lattice repeat of 13.623(1) A. The anions with the metal atoms in theA-face centers and the cations form a “mixed stack” along the short diagonal of theab-plane. The short interplanar distances (C−A=A−C=3.43 A and C-C=3.91 A) in the mixed stack (CAC-CAC⋯) show the possibility of unusual electrical behavior. There is no evidence of direct or indirect metal-metal interaction.

Crystal and molecular structure ofN-methylphenazinium bis(benzene-1,2-dithiolato)nickelate(III). Structure of (C13H11N2)[Ni(S2C6H4)2]

Structure of (N,N'-o-phenylene-disalicylideneaminato)nickel(II), [Ni(C20H14N2O2)]

Cristallisation dans P2 1 /c avec affinement respectivement jusqu'a 0,062 et 0,073. Les deux complexes ont une configuration pseudo plan carre. La piperidine adopte une conformation chaise

Structures of bis(piperidine-1-dithiocarbamato)nickel(II) and bis(piperidine-1-dithiocarbamato)copper(II)

Superionic conducting glass of the mole percent 60% Ag I-20% Ag 2 O-20% MoO 3 was prepared by rapid quenching from the melt. EXAFS and X-ray RDF studies indicate the presence of strong Ag-I interactions with r Ag-I =2.87 A. Two Ag-O interactions whose distances differ by 0.38 A are also indicated. X-Ray RDF studies also yield r Mo-O =2.1 A and the coordination number of oxygen around Mo, n Mo-O =5.7. A model is proposed which consists of a three dimensional network of distorted MoO 6 octahedra, which are 6, 4, and 2-corner shared leading to large channels in the structure. The Ag + ions form bonds and secondary interactions with both non-bridging and bridging oxygen atoms in the network. The I - ions surround the Ag + ions in the voids created by the glass network. The results show that Ag + and I - ions are highly dispersed in the glass network and cluster formation was not found as proposed by earlier workers.

M. Seshasayee

Papers

An X-ray RDF study of Li2O_P2O5_LiCl glasses

Crystal and molecular structure ofN-methylphenazinium bis(benzene-1,2-dithiolato)nickelate(III). Structure of (C13H11N2)[Ni(S2C6H4)2]

Structure of (N,N'-o-phenylene-disalicylideneaminato)nickel(II), [Ni(C20H14N2O2)]

Structures of bis(piperidine-1-dithiocarbamato)nickel(II) and bis(piperidine-1-dithiocarbamato)copper(II)

Structural Studies on Superionic Glass AgI-Ag2O-MoO3