Some examples which show a cross-section of the research activities in connection with X-ray structure determinations for different research groups at the ACI.

1)

The structure of Cu(OH)₂, determined from a tiny single crystal (space group Cmc2₁) (H.R. Oswald et al., Acta Cryst. C46, 2279-2284 (1990)) was shown to satisfy the structural criteria for ferroelectricity: S.C. Abrahams, J. Ravez, A. Simon, A. Reller, H.R. Oswald, J. Appl. Cryst. 28, 594-598 (1995).

2)

Superstructures of the basic nitrates Cd(OH)NO₃.H₂O and Ca(OH)NO₃.H₂O (crystallizing in space group Pbca) are stabilized via OH^...O hydrogen bonds: C. Padeste, H.W. Schmalle, H.R. Oswald, Z. Krist. 200, 35-46 (1992).

3)

A new cobalt-ethylenediamine-vanadate [Co(en)₃]³⁺₂ V₂O₇^4- HVO₄^2- . 6H₂O (space group P1) has been studied by using X-ray analysis, thermogravimetry and simultaneous mass spectrometry, and scanning electron microscopy. Decomposition products were tested with respect to its catalytic activity for the reduction of NO with CO: S. Aschwanden, H.W. Schmalle, A. Reller, H.R. Oswald, Mat. Res. Bull. 28, 575-590 (1993).

4)

The structure of SrIrO₃ is perovskite related and has cubic symmetry (space group I2/m3) in which pairs of edge-sharing SrO₆ octahedra are alternately linked via apical oxygens to the unshared edges of other octahedron pairs, forming a 3-D body-centered framework. The high temperature phase of KSbO₃, determined by electron diffraction, is isostructural with SrIrO₃: H. Schmalle, Ch. Gurtner, H.R. Oswald, A. Reller, Z. Krist. 191, 239-247 (1990).

5)

Tiny twinned crystals of Bernalite, Fe(OH)₃, a new mineral from Broken Hill, New South Wales, were examined and refined in different space groups. This mineral also has a perovskite related structure: W.D. Birch, A. Pring, A. Reller, H.W. Schmalle, Amer. Miner. 78, 827-834 (1993).

6)

The twin structure of the perovskite related phase La₂Ti₂O₇ was determined in combination with X-ray and TEM analyses: H.W. Schmalle, T. Williams, A. Reller, A. Linden, J.G. Bednorz, Acta Cryst. B49, 235-244 (1993).

7)

The semiconducting perovskite related phase Sr₅Nb₅O₁₇ was determined by X-ray analysis in space group Pnn2. A redetermination of the structure is in progress, and physical measurements such as second harmonic generation (SHG), DSC and the detection of piezo- and pyroelectricity are necessary to resolve the centrosymmetric/non-centrosymmetric ambiguity of the structure (collaboration with S.C. Abrahams, USA).

8)

Metal complexes of 6-mercaptopurine (MP) may probably be used as prodrugs of MP and enhance its pharmacological efficiency. A detailed discussion, based on several X-ray structure determinations, is given in the review article: Metal complexes of sulfur-containing purine derivatives: E. Dubler, in Metal Ions in Biological Systems, Vol. 32, 301-337 (1996). ed. A. Sigel & H. Sigel, Basel.

9)

Quantum chemical calculations on purine derivatives (such as hypoxanthine, xanthine, allopurinol, alloxanthine), using semiempirical and ab initio geometry optimizations, were found to agree well with results of X-ray structure determinations of protonated, deprotonated and metal-coordinated purines: M. Nonella, G. Hänggi, E. Dubler, J. Mol. Struct. (Theochem) 279, 173-190 (1993).

10)

The interaction of transition metals with the coenzyme alpha-lipoic acid: Synthesis, structure and characterization of copper and zinc complexes: M.R. Baumgartner, H. Schmalle, E. Dubler, Inorg. Chim. Acta, 252, 319-331 (1996).

11)

Several copper-, cobalt- and cadmium-complexes of the antiviral drug acyclovir (acycloguanosine) have been characterized by X-ray analyses: E. Dubler et al., in preparation.

12)

A trichloro-dihydropterin-oxomolybdenum(IV) complex has been proposed as a functional and structural model for the Mo-pterin binding site in dimethyl sulfoxide reductase: B. Fischer, H. Schmalle, E. Dubler, A. Schäfer, M. Viscontini, Inorg. Chem. 34, 5726-5734 (1995).

13)

Two new homoleptic polynuclear copper(I) thiolates have been characterized by X-ray crystallography, thermal analyses, luminescence- and IR-spectroscopy: M. Baumgartner, H. Schmalle, E. Dubler, Polyhedron 9, 1155-1164 (1990).

14)

Three homoleptic copper(I) thiolates could be synthesized by a new technique and were structurally characterized by X-ray powder- and single-crystal analyses: M. Baumgartner, H. Schmalle, Ch. Baerlocher, J. Solid State Chem. 107, 63-75 (1993).

15)

Different homoleptic Fe-squarato complexes have been synthesized and structurally characterized: M. Baumgartner et al., in preparation.

As chemistry is moving from molecular to supramolecular systems, the molecular-magnetic materials group concentrates on a synthetic strategy which leads to extended two- and three-dimensional coordination compounds. The 3-D systems inherently exhibit a helical chirality and consequently the homometallic compounds crystallize in either one of the enantiomorphic cubic space groups P4₃32 or P4₁32. Analogous heterometallic stoichiometries crystallize in the cubic space group P2₁3. Overall, a large variety of 3-D supramolecular host-guest systems with interesting intramolecular connectivities, intermolecular contacts and chiral topologies represent a fascinating challenge for crystallographic studies:

16)

Photochemical Synthesis and Structure of a 3-Dimensional Anionic Polymeric Network of Tris(2,2'-bipyridine)iron(II) Cations: S. Decurtins, H.W. Schmalle, P. Schneuwly, H.R. Oswald, Inorg. Chem. 32, 1888-1892 (1993).

17)

A Concept for the Synthesis of 3-Dimensional Homo- and Bimetallic Oxalate-Bridged Networks [M₂(ox)₃]_n. Structural, Mössbauer, and Magnetic Studies in the Field of Molecular-Based Magnets: S. Decurtins, H.W. Schmalle, P. Schneuwly, J. Ensling, P. Gütlich, J. Am. Chem. Soc. 116, 9521-9528 (1994).

18)

Chiral, 3-Dimensional Supramolecular Compounds: Homo- and Bimetallic Oxalate- and 1,2-Dithiooxalate-Bridged Networks. A Structural and Photophysical Study: S. Decurtins, H.W. Schmalle, R. Pellaux, P. Schneuwly, A. Hauser, Inorg. Chem. 35, 1451-1460 (1996).

Caused by the template effect of different counterions, the crystallization and structural characterization of 2-D extended network structures has also successfully been accomplished:

19)

A polymeric two-dimensional mixed-metal network. Crystal structure and magnetic properties of {[P(Ph)₄][MnCr(ox)₃]}_n: S. Decurtins, H.W. Schmalle, H.R. Oswald, A. Linden, J. Ensling, P. Gütlich, A. Hauser, Inorg. Chim. Acta 216, 65-73 (1994).

In the course of the evaluation of the magnetic structures, neutron diffraction experiments were carried out at different temperatures (from 300 K to 1.7 K) in order to obtain the structural and magnetic neutron diffraction patterns. The combined efforts of the X-ray structural investigations in Zürich and the neutron scattering experiments at the ILL in Grenoble and at the HMI in Berlin result in the elucidation of the different magnetic phases:

20)

Three-dimensional helical supramolecules - the elucidation of magnetic ordering for an antiferromagnetic phase: S. Decurtins, H.W. Schmalle, R. Pellaux, R. Huber, P. Fischer, B. Ouladdiaf, Adv. Mater., 8, 647-651 (1996).

A new method for the preparation of tin tungsten bronzes under mild conditions and subsequent high-temperature treatment revealed a non-stoichiometric polycrystalline material Sn_xWO₃ (x=0.26 - 0.33). A hexagonal and a modulated orthorhombic phase were observed:

21)

Crystal structure of a hexagonal tin tungsten bronze prepared by a mild reaction: Xao-Lin Xu, H.W. Schmalle, J. R. Günter, Solid State Ionics 76, 221-228 (1995).

22)

The elucidation of the modulated structure (together with Wulf Depmeier, University of Kiel) is in progress. In a first trial refinement 18 tungsten, two tin and 52 oxygen atoms were treated as a superstructure in the space group Cmma. The refinement of a model as a commensurate modulated structure in the super-space group Acmm (00[gamma]) is in progress.

23)

The structure of Cu₂SnS₃, three-dimensionally disordered, is under investigation. A model of the average structure (1/8 of the unit cell volume of the superstructure) could be refined in the space group P121 for the metrically pseudo-cubic subcell: J.R. Günter et al., in preparation.

Collaborations with the ETH group of Walter Schneider, emeritus, and Kaspar Hegetschweiler, who is now at the University of Saarbrücken, revealed interesting X-ray crystallographic results:

24)

Synthesis and Structure of a Novel Hexanuclear Iron(III) Complex Containing Six Terminal and Twelve Bridging Alkoxo Groups and one mu⁶-Oxo Bridge: K. Hegetschweiler, H. Schmalle, H.M. Streit, W. Schneider, Inorg. Chem. 29, 3625-3627 (1990).

25)

Two Isomeric Chromium(III) Complexes with 1,3,5-Triamino-1,3,5-trideoxy-cis-inositol in One Structure: H.W. Schmalle, K. Hegetschweiler, M. Ghisletta, Acta Cryst. C47, 2047-2052 (1991). The inositol ligand is able to provide four different binding sites, of which two were realized in this structure: one Cr(O₃N₃) and one Cr(O₆) coordination complex, were found together with four sulfate groups and 30 water molecules in the unit cell.

26)

Hydrogen Bonding versus van der Waals Repulsion in 1,3,5-Trideoxy-1,3,5-tris-(trimethylammonio)- cis-inositol Triiodide Sesquihydrate: H.W. Schmalle, K. Hegetschweiler, Acta Cryst. C52, 1288-1293 (1996).

Out of a large number of publications from Heinz Berke's group only a few examples are given here:

27)

An Unusual Example of H₂ Coordination by a d⁴ Metal Center: Reactions between OsH₂Cl₂(P-i-Pr₃)₂ and H₂: D.G. Gusev, V.F. Kuznetsov, I.L. Eremenko, H. Berke, J. Am. Chem. Soc. 115, 5831-5832 (1993).

28)

Hydrogen/Hydrogen Exchange and Formation of Dihydrogen Derivatives of Rhenium Hydride Complexes in Acidic Solutions: S. Feracin, T. Bürgi, V.I. Bakhmutov, I. Eremenko, E.V. Vorontsov, A.B. Vimenits, H. Berke, Organometallics 13, 4194-4202 (1994).

29)

The Reduction of [Fe(CO)₂L₂X₂] (L=P(OMe)₃, P(OiPr)₃, PEt₃; X=Br, I) -- From Iron(II) to Iron(0) via Stable Iron(I) Intermediates: H. Kandler, C. Gauss, W. Bidell, S. Rosenberger, T. Bürgi, I.L. Eremenko, D. Veghini, O. Orama, P. Burger, H. Berke, Chemistry Eur. J. 1, 541-548 (1995).

30)

Synthesis of Nitrosyl Re(I) Complexes Bearing Bidentate Ligands: D. Veghini, S.E. Nefedov, H. Schmalle, H. Berke, J. Organometallic Chem. 526, 117-134 (1996).

• Back to the History of Crystallography at the University of Zürich