Determination of Diaryliodonium Species by Reverse Iodometric Titration with Ascorbic Acid

Diaryliodonium salts are used in organic chemistry, materials science and pharmaceutical chemistry. For the quantitative analysis of diaryliodonium salts, only instrumentally demanding techniques requiring highly skilled operators are available. Surprisingly, no titration method taking advantage of the oxidising ability of diaryliodonium is available in the literature. In the present work, a titration method for the determination of diaryliodonium salts is presented. It is based on the reaction of diaryliodonium species with ascorbic acid, whose excess is subsequently determined by means of iodometric potentiometric titration. Application of the protocol to various diaryliodonium salts revealed the scope and limitations of the method.     

Self‐Assembly of 1,1′‐Biphenyl‐2,2′,6,6′‐tetracarboxylic Acid: Formation of an Achiral Grid with Chiral Compartments

D ₄ ‐symmetric chiral hydrogen‐bonded cyclotetramers (see the structure in the picture) are present in the self‐assembled achiral title compound in the solid state. The unilayered network set up from the chiral “square” blocks is achiral as a consequence of the crystal symmetry.     

Determination of mechanical properties by instrumented indentation

The paper reviews the current state of the depth-sensing indentation (sometimes called nanoindentation), where the information on material behaviour and properties is obtained from the indenter load and depth, measured continuously during loading and unloading. It is shown how the contact parameters and principal characteristics are determined using pointed or spherical indenters. Indentation tests can be used for the measurement of hardness and elastic modulus, and also of the yield stress and for the construction of stress–strain diagrams, for the determination of the work of indentation and its components. Most devices use monotonic loading and unloading, but some also enable measurement under a small harmonic signal added to the basic monotonously increasing load. This makes possible continuous measurement of contact stiffness and the study of dynamic properties and the determination of properties of coatings. One section is devoted to the measurement on viscoelastic-plastic materials, where the delayed deforming must be considered during the measurement as well as in data evaluation. Instrumented indentation can also be used for the study of creep under high temperatures. The paper also discusses the errors arising in depth-sensing measurements and informs briefly about some other possibilities of the method.     

Ab initio calcuation of ideal strength for cubic crystals under three-axial tension

Ab initio calculation of ideal strength of cubic crystals under three-axial tension was performed using the LMTO-ASA method. Computed values are in a good agreement with those obtained previously by means of semi-empirical polynomial approach. The values of equilibrium lattice parameter obtained in the framework of ab initio method are well comparable with the experimental data whereas a less satisfactory agreement was achieved in the case of bulk moduli.     

Certain Liouville series

Abstract The main results of this paper give two criteria for certain infinite series of rational numbers to be Liouville. Some examples are also included. Keywords: Liouville numbers, Infinite series Mathematics Subject Classification (2000): 11J82     

Expressible sets of sequences with Hausdorff dimension zero

We give conditions sufficient for sequences consisting of real numbers to ensure that their expressible sets have Hausdorff dimension zero.     

Structure and in vitro antifungal activity of [2,6‐bis(dimethylaminomethyl)phenyl]diphenyltin(IV) compounds

A set of seven [2,6‐bis(dimethylaminomethyl)phenyl]diphenyltin(IV) ({[(CH₃)₂NCH₂]₂(C₆H₃)}­(C₆H₅)₂Sn⁺X^?) ionic organotin(IV) compounds (X = Br, NO₃, CN, SCN, SeCN, BF₄ and PF₆) has been prepared and characterized by electrospray ionization mass spectrometry, ¹H NMR spectroscopy in CDCl₃,¹¹⁹Sn NMR in CDCl₃ and DMSO‐d₆ solution, as well as by ¹³C and ¹¹⁹Sn CP/MAS NMR spectroscopy and X‐ray diffraction techniques in the solid state. The in vitro antifungal activity of these water‐soluble ionic organotin(IV) compounds was compared with starting compounds and the antifungal drugs currently in clinical use. Copyright © 2002 John Wiley & Sons, Ltd.