Synthesis and Structural Analysis of a Helical Coordination Polymer Formed by the Self-Assembly of a 2,2′-Bipyridine-Based exo-Ditopic Macrocyclic Ligand and Silver Cations

The overall topology of coordination polymers can be controlled by means of the coordination preferences of the metal center and the structure of the bridging ligand. This is demonstrated here by the synthesis of a single-stranded helical coordination polymer by the self-assembly of the exo-ditopic ligand 1 and silver ions.     

Copolymerization of hexafluoropropylene and tetrafluoroethylene: Effect on chain conformation and crystal structure

A series of new copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) containing up to 50 mol % of the hexafluoropropylene comonomer have been investigated with respect to chain conformation and crystal structure using wide-angle X-ray diffraction (WAXD). Increasing HFP content leads to significant departures from the highly ordered crystalline structure of the homopolymer PTFE; the helical conformation of the chain relaxes and untwists to accommodate the larger  CF₃ pendant group in the HFP unit. Simultaneously the lateral hexagonal packing of the helices becomes less ordered and the a-dimension of the hexagonal cell increases. The above effects are progressive with increasing HFP content. At 50 mol % HFP incorporation the structure is a disordered crystalline phase. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2811–2819, 1998     

Analysis of the Symmetry of Crystal Packing Forces by Methyl Proton Tunneling: A Strategy for the Unambiguous Assignment of the Magnetic Jahn – Teller Effect in Molecules

Intrinsic and extrinsic forces behind the distortion in metal atom clusters can be readily distinguished provided that the clusters are embedded in a suitable ligand environment and that the tunneling of the protons in the peripheral ligands is then analyzed by inelastic neutron scattering. For the [Cr₃O(OOCCH₃)₆(H₂O)₃]Cl⋅6 H₂O model system studied, the tunneling process is very sensitive to the local environment. Thus a tool is available to allow a better assessment of the cause of structural distortions.     

Synthesis and Structure of Potassium 1‐Benzylimidazole‐2‐carboxylate · 2/3Hydrate

The title compound, K[bimCO₂] · 2/3H₂O (C₁₁H₁₉N₂O₂K · 2/3H₂O), has been synthesized, and characterized by a single crystal X‐ray study; it has the grouping cross‐linked into a polymeric sheet in which potassium environments are diverse and unsymmetrical, containing six‐coordinate and seven‐coordinate geometries.     

A predictive vapor-pressure equation

A simple equation is presented for predicting the temperature dependence of the vapor-pressure of a pure substance along the entire (liquid + vapor) coexistence curve, from the triple point to the critical point. The proposed equation is based on the use of a dimensionless temperature reduced by using critical and triple point values, and of the Clausius–Clapeyron equation as a zeroth-order approximation. The pressure and temperature at the triple point, the normal boiling temperature, and the pressure and temperature at the critical point are required as input data. The proposed equation is verified for 53 fluids by using NIST data. These data are reproduced with an overall average deviation of 0.55%.     

After OR: An Agenda for Postmodernism and Poststructuralism in OR

Postmodernism and poststructuralism have only been mentioned in passing within this journal. There is much more to be said, and this paper aims to open up the debate, to begin to explore the vast terrain and to present one/some agenda/s for the future, introducing some of the ideas that have inspired O(u)R practice. The paper is in four episodes. We begin by exploring the differences between modernism and postmodernism and introducing some of our sources (episode 1), moving on to the study of language through structuralism and into poststructuralism (episode 2). This section introduces some key concepts and approaches which we illustrate in a short case study (episode 3) of the language of OR. The final section (episode 4) sketches in the outlines of our future agenda. A warning is in order for people unfamiliar with postmodernism: the terminologies and style may seem unusual and untraditional for the journal.     

NMR imaging in solids

The use of NMR imaging for the study of solids is demonstrated. A modified version of the convolution algorithm is used to construct the images. The modification removes the NMR linebroadening as the image is formed. Examples are presented using the mixed ionic conductor (Na_1?x, K_x) β-alumina.