Poster Sessions C700 MS80.P04 Acta Cryst. (2011) A67, C700 Thermal and photocrystallographic studies on a nickel-nitro complex Lauren Hatcher, Mark Warren, Paul Raithby, Department of Chemistry, University of Bath, Bath, BA2 7AY (UK) . E-mail: leh29@ bath.ac.uk The technique of time-resolved crystallography has attracted much interest in recent years, as a result of rapid technological advancements in the feld. These methods introduce the “fourth dimension” of time into the crystallographic experiment, allowing the structures of short- lived and metastable species to be determined [1]. In this work, nitro-(η 1 -NO 2 ) to nitrito-(η 1 -ONO) linkage isomerisation in the complex [Ni(Et 4 dien)(NO 2 ) 2 ] (Et 4 dien = N,N,N’,N’-tetraethyldiethylenetriamine) has been studied using time- resolved crystallographic techniques. Signifcant levels of conversion are induced in the single-crystal when the complex is excited both photochemically and thermally. 86% conversion to the metastable nitrito-(η 1 -ONO) linkage isomer is achieved following irradiation with UV light, and a maximum 42% conversion is thermally induced when variable temperature studies are conducted between 100 K and 370 K. This is the frst crystallographic study to report both thermal and photochemical excitation of the nitrite ligand in the same system. [1] P. Coppens, I.I. Vorontsov, T. Graber, Acta Cryst. A. 2005, 61, 162. Keywords: photocrystallography, photoactivation, nitrite MS80.P05 Acta Cryst. (2011) A67, C700 Crystal structure and luminescence properties of lanthanide- containing organic complexes Laure Guénée, a Jean-François Lemonnier, b Tomasz A. Wesolowski, b Stéphane Petoud, c Claude Piguet, b a Laboratory of Crystallography, University of Geneva (Switzerland) . b Inorganic Chemistry Department, University of Geneva. c Centre de Biophysique Moléculaire, CNRS, Orléans (France). E-mail: laure.guenee@unige.ch In order to rationalize and design luminescent lanthanide- containing organic complexes, the central phenyl ring separating 2,6- bis(benzimidazol-2-yl)pyridine binding units in the bis-tridentate model ligands L 1 -L 3 were substituted with neutral (R=H, L 1 ), electro-attracting (R=F, L 2 ) or electro-donating (R=OCH 3 , L 3 ) groups. Reaction of these ligands with Ln(hfac) 3 salts give poorly soluble dinuclear single strand complexes [Ln 2 L i (hfac) 3 ] (i=1-3). X-Ray single crystal structure analyses revealed that the stepwise connection of bulkier substituent onto the central phenyl ring (R=H < R=F ~ R=OCH 3 ) increases the inter-annular phenyl-benzimidazole interplanar angles (25°<a<54°). This structural feature is expected to affect the HOMO-LUMO gap in the various complexes (as exemplifed by TD-DFT calculations for the ligands in gas-phase). Solid state photophysical properties on [Eu 2 L i (hfac) 3 ] (i=1-3) revealed that the ligand-to-metal energy transfer is signifcantly affected by the choice of the substituent and we conclude that the electro- attracting substituent F is the best candidate simultaneously matching structural and solution properties, and photophysical characteristics. Keywords: lanthanide, luminescence, polyaromatic ligands MS81.P01 Acta Cryst. (2011) A67, C700-C701 Flux growth of piezoelectric single-crystals from the SiO 2 -GeO 2 binary diagram Adrien Lignie, a Pascale Armand, a Guillaume Fraysse, a Julien Haines, a Philippe Thomas, b Philippe Papet, a a Institut Charles Gerhardt Montpellier, UMR5253 CNRS-UM2-ENSCM-UM1, C2M, UMII, CC1504, Place E. Bataillon, 34095 Montpellier Cedex 5, (France). b Centre Européen de la Céramique, SPCTS-UMR CNRS 6638, 12, rue Atlantis, 87068 Limoges, (France). E-mail: adrien.lignie@univ- montp2.fr Nowadays, synthetic α-quartz is still the most extensively used piezoelectric material. Its zero temperature coeffcients cut (AT-cut) and its low acoustic loss are exploited in Surface Acoustic Waves devices (flters, oscillators, resonators...). However, its piezoelectric properties are limited in temperature due to its transition towards the non piezoelectric β-quartz phase, which occurs at 573°C. Besides, its electromechanical coupling coeffcient is low (k=11%) considering those obtained by PZT ceramics (k=60-90%). In order to increase the electromechanical coupling coeffcient and the thermal stability domain, the solid-solution between SiO 2 and GeO 2 , a quartz analog, was investigated. The main interest of GeO 2 is its high structural distortion: in theory, as regards to previous studies on the α-quartz homeotype family, its piezoelectric performances, linked to distortion, should be three times higher. Furthermore, no α/β-quartz phase transition appears in α-GeO 2 . Both parts of the Ge 1-x Si x O 2 solid- solution were studied. The rich SiO 2 -content compositions where some Si 4+ -substitution by Ge 4+ delay the α/β-quartz phase transition and the rich GeO 2 -content compositions where some Ge 4+ -substitution by Si 4+ atoms stabilize the α-quartz phase of GeO 2 (metastable at ambient temperature). The increase of the structural distortion in germanium- substituted SiO 2 compositions should also improve their piezoelectric performances. Single-crystals from both side of the binary SiO 2 -GeO 2 diagram have already been synthesized by the hydrothermal method. However, the use of water as growth medium favors the formation of water inclusions in crystals. These inclusions were avoided by the use of a novel way to grow single-crystal of this system: the high-temperature fux growth technique. The growth process was optimized to enlarge the transparent, colorless and well-facetted crystals obtained. Millimeter- size fux-grown Ge 1-x Si x O 2 single-crystals, crystallizing in the trigonal space group P3 1 21 or P3 2 21, were grown by spontaneous nucleation with the slow cooling method. Different macroscopic morphologies, going from pseudo-cubic shape to hexagonal prism-like shape, were observed depending on the nature of the fux, the substitution content and the sursaturation rate.