Day 3 :
- Track 3: Chemical Crystallography
Location: Houston
Chair
Jean Guillaume Eon
Universidade Federal do Rio de Janeiro, Brazil
Session Introduction
Jean-Guillaume Eon
Universidade Federal do Rio de Janeiro, Brazil
Title: Topological features in crystal structures: A quotient graph-assisted analysis of underlying nets and their embeddings
Time : 10:00 - 10:25
Biography:
Jean-Guillaume Eon completed his PhD from Université de Technologie de Compiègne (France) in 1984. He is the Director of a research group on Oxidation Catalysis at the Federal University of Rio de Janeiro, Brazil. He has published more than 60 papers in chemistry and crystallography journals and has been serving as an Editorial Board Member for Acta Crystallographica, Section A.
Abstract:
Topological properties of crystal structures may be analyzed at several levels, depending on the representation and the topology that have been assigned to the crystal. We consider here the combinatorial or bond-topology derived from the underlying net, which is independent of its embedding in space. Periodic nets representing one-dimensional complexes, or the associated graphs, characterize the skeleton of chemical bonds within the crystal. By topological features we mean the different possible building units that can be used to describe a crystal structure and the mode of connection between these units, independently of the geometrical details of the structure. Such building units can be finite or infinite, corresponding to one-, two- or even three-periodic subnets. Examples of infinite units include linear chains or sheets of corner- or edge-sharing polyhedra. Periodic nets can be represented by their labelled quotient graphs. This presentation will deal with the trace or projection of building units on labelled quotient graphs. Decomposing periodic nets into their building units relies on graph-theoretical methods classiï¬ed as surgery techniques. The most relevant operations are edge subdivision, vertex identiï¬cation, edge contraction and decoration. Instead, these operations can be performed on labelled quotient graphs, evidencing in almost a mechanical way the nature and connection mode of building units in the derived net. Various examples will be discussed with the visual support provided by the program package TOPOS, ranging from ï¬nite building blocks to three-periodic subnets. Among others, the structures of strontium oxychloride, spinel, lithiophylite and garnet will be addressed.
Yuichi Shimazaki
Ibaraki University, Japan
Title: X-ray crystal structures of the one-electron oxidized metal–phenolate complexes; geometric and electronic structures relationship
Time : 10:25-10:50
Biography:
Yuichi Shimazaki received his Doctor’s degree in Science from Nagoya University in 2000 under the supervision of Professor Osamu Yamauchi. He joined Professor Yoshinori Naruta’s group at Kyushu University as Assistant Professor and worked on the redox behavior of various metal porphyrin complexes as models of the active site of metalloenzymes. In 2008, he was promoted to Associate Professor at the College of Science, Ibaraki University. His research interests include the oxidation chemistry of the complexes of various metal ions, model studies of metalloenzymes, bioorganometallic chemistry, and weak interactions in metal-organic molecule systems.
Abstract:
Oxidation chemistry of redox active transition metal complexes with pro-radical ligands and their detailed electronic structures have been actively pursued in recent years. An “experimental” valence state of metal complexes is sometime different from the “formal” oxidation state, especially in the species having redox active ligands. This difference can be seen in biological system, such as iron(IV)-porphyrin p-cation radical in some heme proteins and copper(II)-phenoxyl radical in galactose oxidase (GO). Many efforts for determination of the experimental oxidation number have been close to the goal of the “truth oxidation state” in various oxidized metal complexes with redox-active ligands. Depending on the relative energies of the redox-active orbitals, metal complexes with non-innocent ligands exist in two limiting descriptions, either a metal-ligand radical (Mn+(L·)) or a high valent metal (M(n+1)+(L-)) complex. The reaction mechanisms of artificial and biological catalysts depend on the electronic structures of the high valent intermediates. However, structural characterizations of these species by X-ray diffraction methods have been rare due to their stability. Recently, some artificial metal−phenoxyl radical complexes as models of GO have been synthesized and successfully characterized by X-ray crystal structure. The one-electron oxidized metal-phenolate complexes showed various electronic structures depending on small perturbations, such as substitution of the phenolate ring and the chelate effect of the phenolate ligands and so on. In this presentation, I will focus on X-ray crystal structures of the one-electron oxidized metal–phenolate complexes in the case of metal complexes of diphenolate Schiff base ligands with 2N2O donor sets. Especially electronic and crystal structure relationship such as differences of metal-phenoxyl radical and high-valent metal phenolate complexes will be discussed.
Boniface P T Fokwa
University of California-Riverside, USA
Title: Magnetic ordering, frustration and possible spin liquid state from 1D Cr3-triangles in the TiCrIr2 xOsxB2 series
Time : 11:10-11:35
Biography:
Boniface P T Fokwa completed his PhD in 2003 from the Dresden University of Technology (Germany) and Post-doctoral studies from the RWTH Aachen University (Germany). He is an Associate Editor for Encyclopedia of Inorganic and Bioinorganic Chemistry (Wiley). He has published more than 70 papers in reputed journals and has won several awards including the prestigious Heisenberg Fellowship from the German Research Foundation and was Visiting Scientist at University of Auckland (New Zealand) and Cornell University as well as Visiting Professor at UCLA.
Abstract:
A new series of compounds TiCrIr2‑xOsxB2 (x=0-2) was successfully synthesized and characterized using X-ray diffraction as well as energy-dispersive X-ray analysis. All members of the series crystallize in the hexagonal non-centrosymmetric Ti1+xOs2-xRuB2 structure type (space group P2m, no. 189, Pearson symbol hP18). The structure contains trigonal planar B4 units strongly interacting with triangles of magnetically active Cr atoms, which are stacked on each other to form isolated Cr3-chains along the c-axis. Magnetization measurements of TiCrIr2B2 (34 valence electrons, VE) reveal ferrimagnetic behavior below TC=275 K with a large, negative Weiss constant of -750 K. Density functional theory calculations demonstrate magnetic frustration due to indirect antiferromagnetic interactions within the Cr3 triangles competing with direct ferromagnetic interactions. Tuning the valence electron count by replacing Ir with Os changes the magnetic behavior in the series. Magnetization measurements of TiCrIrOsB2 (33 VE) and TiCrOs2B2 (32 VE) exhibit paramagnetic behavior with features reminiscent of the spin liquid state. Interestingly, the crystal orbital Hamilton population (COHP) of TiCrIr2B2 indicates Cr-Cr antibonding interactions above 32.9 VE, but part of the Cr-Cr antibonding region is already occupied in TiCrOs2B2 even though it has 32 valence electrons. Therefore, the TiCrIr2‑xOsxB2 (x=0-2) series do not follow rigid band approximation.
Takeru Ito
Tokai University, Japan
Title: Oxide cluster-surfactant hybrid single crystals toward solid electrolyte
Time : 11:35-12:00
Biography:
Takeru Ito has received his Doctor’s degree in 2001 at the University of Tokyo. After his Post-doctoral studies from the University of Tokyo and Tokyo Institute of Technology, he was appointed as an Assistant Professor at the Tokyo Institute of Technology. He moved to Tokai University in 2008, and now he is an Associate Professor. His research interests are focused on the synthesis and functionalization of Polyoxometalate Surfactant Hybrid Crystals.
Abstract:
To synthesize highly conductive materials is crucial for lithium-ion or fuel-cell battery technology due to their structural stability and easiness for handling. A promising strategy is to hybridize inorganic and organic molecular components and to construct crystalline layered structures beneficial to the emergence of conductive property. Polyoxometalate oxide cluster anions having characteristic redox properties are suitable as inorganic components. Polyoxometalates can be hybridized with cationic surfactants to form stable layered single crystals. Such ionic crystals are rare, and both polyoxometalate and surfactant components can be variously selected to build up functional inorganic-organic hybrid crystals. The polyoxometalate-surfactant hybrid crystals were synthesized by cation-exchange reaction with pH-adjusted solutions of molybdate, tungstate, and vanadate oxoanions. Single crystals were obtained from the filtrate solutions or by recrystallization of the crude precipitates, and subjected to X-ray structure analyses. Decatungstate and tetra-molybdate anions formed stable single crystals together with hexadecylpyridinium. The crystals exhibited the alternate stacking of polyoxometalate inorganic layers and surfactant organic layers. The obtained conductivity values were in the range of 10−6 to 10−5 S cm−1 order over 423 K under anhydrous atmosphere. Decavanadate anion formed layered crystals with alkyltrimethylammonium. The hybrid crystals which comprise diprotonated decavanadate species exhibited anhydrous proton conductivity at intermediate temperatures (>373 K), which is possible for proton-conducting electrolyte of fuel cells.
Marietjie Schutte-Smith
University of the Free State, South Africa
Title: The investigation of chemical crystallography and kinetic reactivity of Re(I) tricarbonyl complexes
Time : 12:00-12:25
Biography:
Marietjie Schutte-Smith has completed her PhD at the University of the Free State, Bloemfontein, South Africa. She was appointed as a Lecturer immediately after the completion of her PhD from 2012 and were promoted to Senior Lecturer in 2016. She is supervising two MSc and six PhD students and she has published 21 articles.
Abstract:
The coordination chemistry of rhenium and technetium has gained major interest for the possible use in radiopharmacy, due to several favorable properties. A number of fac-[M(CO)3]+ (M=Re, 99mTc) type complexes have been synthesized to date with a large number of ligand systems. The three labile aqua ligands on the starting synthon fac-[Re(CO)3(H2O)3]+ can easily be substituted by a variety and/or combinations of ligands producing stable compounds and potential radiopharmaceuticals with many different characteristics. We focus on the fac-[Re(CO)3]+ moiety and related compounds by adopting the [2+1] approach. The solid state behaviour and the effects like the charge, the donor atoms and electron donating and withdrawing effects of the ligands coordinated to the metal are explored. The influence of the coordinated bidentate ligands on the rate of substitution by a variety of entering ligands in solution is also investigated. The aqueous kinetics of fac-Re(I) tricarbonyl complexes are virtually unexplored. We synthesized a water soluble complex which allowed us to evaluate the reactivity of a fac-Re(I) tricarbonyl type complexes in aqueous medium which is imperative for biomedical application. The first high pressure substitution kinetics on a fac-[Re(L,L’-bid)(CO)3(CH3OH)] complex are also reported here.
Werner Paschinger
University of Vienna, Austria
Title: Relations between crystal structures and physical properties in the ternary systems CexTySnz (T = Pd or Pt)
Time : 12:25-12:50
Biography:
Werner Paschinger stared his studies in chemistry and physics at the University of Vienna in 2005. In 2013 he received his Bachelor of Science (B.Sc.) and in 2014 his Master of Science (M.Sc.) both from chemistry working on intermetallic compounds and thermoelectric materials within the group of Prof. Rogl at the Department of Physical Chemistry. Since April 2014 he is doing his PhD within the MATFLEXEND project at the Institute of Materials Chemistry & Research under supervision of Prof. Bismarck.
Abstract:
Although hitherto still no phase diagrams exist for the ternary systems CexTySnz (T = Pd or Pt), several compounds of these systems are in the focus of interest due to a number of interesting physical properties. Up to now, they have mainly been characterized by their magnetic properties, but more recently attracted attention due to their possible application as thermoelectric materials. For example, the hybridization of the 4f state of the Ce atom with conduction electrons of T and Sn atoms in Ce3Pt3Bi4 and CeRu4Sn6 or Ce4Pt12Sn25 with complex structures gives rise to a large thermopower, which is one of the prerequisites for thermoelectric application. For a proper interpretation and understanding of physical properties, the knowledge of the compounds’ crystal structure is of high importance. Therefore the relation of physical properties to structural motives in both systems will be discussed and compared to each other. Furthermore, we will introduce the crystal structure of two novel ternary compounds, CePd3Sn2 and Ce3Pt4Sn6, derived by direct methods from X-ray single crystal data. Whereas CePd3Sn2 crystallizes in an orthorhombic structure, Ce3Pt4Sn6 seems to coexist in a monoclinic and orthorhombic modification. For the monoclinic structure an intrinsically defect growth pattern was found backed by high resolution TEM. Structural units intrinsic to the title systems will be compared as well as to other related defect structures.