Azo and azoxythiacrown ethers: synthesis and properties

A series of 16- and 18-membered azo- and azoxythiacrown ethers have been synthesized by reductive macrocyclization of the respective bis(nitrophenoxy)oxaalkanes. The aromatic residues located in the polyether region of the molecule were introduced to macrocyclic skeletons and their affinities toward different groups of metal cations in ion-selective electrodes were described. X-ray structures for one dinitropodand and one azoxybenzothiacrown exhibiting strong π–π and π–H interactions have been found.     

Whiskers growing from aqueous solution of natrium molybdate

A special apparatus was built for continuous measurements of concentration changes caused by whiskers growing in polymolybdate solutions.     

Eine Grlaselektrode zur Indizierung der direkten potentiometrischen Kaliumtitration mit Hexafluorosilicat

Zusammenfassung Aus einem Natriumaluminiumsilicat-Glas mit der Synthese-Zusammensetzung (Mol-%) 27% Na₂O, 8% Al₂O₃ und 65% SiO₂ (NAS 27-8) wurden Glaselektroden hergestellt, deren Eignung zur Indizierung der Kaliumtitration mit Zn[SiF₆] in methanoliseher Lösung untersucht wurde. In reinen, schwach sauren Kaliumsalzlösungen erhält man gut auswertbare Titrationskurven. Die Glaselektrode versagt in stark saurer Lösung. Außer den Ionen, die mit Hexafluorosilicat schwerlösliche Salze bilden, stören auch Ca²⁺, Mg²⁺ und Al³⁺, die mit den im Gleichgewicht vorliegenden Fluoridionen reagieren.

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Summary Glass electrodes have been prepared from a sodium-alumina-silica glass of the synthesis composition (mole %) of 27% Na₂O, 8% Al₂O₃, 65% SiO₂ (NAS 27-8) and their suitability for the indication of the potassium titration by means of Zn[SiF₆] in methanolic solution has been studied. With pure potassium salt solutions of low acidity it is possible to obtain well definable titration curves. With strongly acid solutions the glass electrode fails. Apart from ions forming sparingly soluble salts with hexafluorosilicate also Ca²⁺, Mg²⁺, and Al³⁺ are interfering by reaction with the fluoride ions present in equilibrium.

     

Synthesis and Structural Studies of New (Triphenylphosphine)(trialkoxysilanethiolato)gold(I) Complexes

Compounds of general formula Au{SSi(OR)₃}(PPh₃), R = Prⁱ ( 1 ), Bu^s ( 2 ) or Bu^t ( 3 ), have been obtained by reaction of AuCl(PPh₃) with triethylammonium salts of respective silanethiols, (RO)₃SiSH. Molecular and crystal structures of 1 , 2 , and 3 have been determined by the single crystal X‐ray structural analysis. Compounds 1 and 2 are the first structurally characterized metal derivatives of hydrolytically unstable trialkoxysilanethiols (PrⁱO)₃SiSH and (Bu^sO)₃SiSH.     

The influence of the type of halogen substituent and its position on the molecular conformation,intermolecular interactions and crystal packing for a series of 1‐benzoyl‐3‐(halogenophenyl)thioureas

By the reaction of benzoyl chloride, potassium isothiocyanate and the appropriate halogenoaniline, i.e. 2/3/4‐(bromo/iodo)aniline, we have obtained five new 1‐benzoyl‐3‐(halogenophenyl)thioureas, namely, 1‐benzoyl‐3‐(2‐bromophenyl)thiourea and 1‐benzoyl‐3‐(3‐bromophenyl)thiourea, C₁₄H₁₁BrN₂OS, and 1‐benzoyl‐3‐(2‐iodophenyl)thiourea, 1‐benzoyl‐3‐(3‐iodophenyl)thiourea and 1‐benzoyl‐3‐(4‐iodophenyl)thiourea, C₁₄H₁₁IN₂OS. Structural and conformational features of the compounds have been analyzed using X‐ray diffraction and theoretical calculations. The novel compounds were characterized by solid‐state IR and ¹H/¹³C NMR spectroscopy. The conformations and intermolecular interactions, such as hydrogen bonds, π–π and S(6)…π stacking, and X…O (X = I or Br), I…S and I…π, have been examined and rationalized, together with four analogous compounds described previously in the literature. The set of nine compounds was chosen to examine how a change of the halogen atom and its position on the phenyl ring affects the molecular and crystal structures.     

On the equivalence of a theorem of Kisynski and the Hille-Yosida generation theorem

We show that a theorem of Kisynski on the generation of Banach-algebra homomorphisms of certain convolution algebras is equivalent to the Hille-Yosida theorem on the generation of operator-valued one-parameter semigroups.

     

DFT and NBO theoretical study of protonation of tri-tert-butoxysilanethiol and its anion

Density functional theory (DFT) calculations of geometry optimization at the B3LYP/6-31+G(d) level have been made for the tri-tert-butoxysilanethiolato anion, i.e. (^tBuO)₃SiS⁻ [coded A], and its O- and S-protonated derivatives: (^tBuO)₃SiSH (B), (^tBuO⁺H)(^tBuO)₂SiS⁻ (C), (^tBuO)₃SiSH₂⁺ (D) and (^tBuO⁺H)(^tBuO)₂SiSH (E). Energy balances for the protonation of silanethiol B in vacuum and the aqueous phase (using the polarized continuum IPCM model) were considered. Based on theoretical calculations, it was found that protonation on the oxygen atom causes Si–S bond shortening, while protonation on the sulfur atoms results in elongation of the bond. Changeability of the Si–S and Si–O bond lengths was analyzed in terms of the natural bond orbital (NBO) method. Principal electronic delocalizations caused by anomeric effects of the sulfur and oxygen lone pairs interaction with the anti-bonding Si–O orbitals were confirmed by the correlation between the shortening of the Si–S bond length and the elongation of the Si–O bond within the structures of the species A–E.     

Around Schwenninger and Zwart’s zero-two law for cosine families

It is proved that for a cosine family \({\{c(t)\}_{t \in \mathbb{R}}}\) in a normed algebra with a unity e, the following assertions hold: (1) If \({\sup_{t \in \mathbb{R}}\| c(t) - e \| < 2}\), then c(t) =  e for every \({t \in \mathbb{R}}\). (2) If \({\lim sup_{t \to 0}\| c(t) - e \| < 2}\), then \({\lim_{t \to 0} c(t) = e}\). It is also shown that the two respective results, each specific for one of the assertions, are equivalent.