Spectroscopic Characterization of Eu(III) Complexes with New Monophosphorus Acid Derivatives of H<Subscript>4</Subscript>dota

The luminescence lifetimes of europium(III) complexes with new monophosphorus acid derivatives of H₄dota were measured by means of time-resolved laser-induced luminescence spectroscopy in H₂O and D₂O. The hydration numbers of these complexes were estimated using different empirical equations [Horrocks and Sudnick (1979) J. Am. Chem. Soc. 101 (1979) 334; Choppin and Barthelemy(1989) Inorg. Chem. 28, 3354–3357; Choppin and Bünzli Lanthanide probes in life, chemical and earth sciences. Theory and practice (1989); Kimura and Kato J. Alloys Comp. 275–277 (1998) 806; Parker (1999) J. Chem. Soc., Perkin Trans. 2, 493–503; Supkowski and Horroks (2002) Inorg. Chim. Acta. 340, 44–48]. It was shown that all the relationships gave similar results with a satisfactory precision. The hydration numbers of complexes of H₃do3a and H₄dota agreed with the literature values. One water molecule is coordinated in complexes of the new ligands. The results showed that the Choppin formula based on measurements only in H₂O can be satisfactorily used for estimation of the hydration numbers.     

One-electron reduction of an "extended viologen" p-phenylene-bis-4,4'-(1-aryl-2,6-diphenylpyridinium) dication

One-electron reduction of the "extended viologen" dication 1 yields the red cation radical 2, characterized by strong near-IR absorption. It has been generated and studied by pulse radiolytic, electrochemical, redox titration, UV-visible, and electron paramagnetic resonance spectroscopic methods. All results are in agreement with a fully delocalized electronic structure for 2.     

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Forthcoming articles     

A direct link between annulene and porphyrin chemistry--21-vacataporphyrin

A novel molecule, aza-deficient porphyrin 5,10,15,20-tetraaryl-21-vacataporphyrin has been synthesised by a substraction of a tellurium atom from 5,10,15,20-tetraaryl-21-telluraporphyrin under treatment of HCl. The new macrocycle is an annulene-porphyrin hybrid and at the same time is directly related to 21-heteroporphyrins but has a vacant space instead of heteroatomic bridge. The molecule preserves the fundamental structural and spectroscopic features of the parental 5,10,15,20-tetraarylporphyrin with three nitrogen atoms and two CH groups favorably prearranged for coordination.     

Equlibrium measure of a product subset of

In this note we show that an equilibrium measure of a product of two subsets of and , respectively, is a product of their equilibrium measures. We also obtain a formula for , where are locally bounded plurisubharmonic functions and .

     

Microcomputer-controlled insturmentation for voltammetric techniques

A simple computer system for conducting voltammetric experiments is described. An Atari 800 XL microcomputer is connected to a laboratory-made analog/digital voltammetric analyzer by means of a two-directional serial transmission interface. The serial transmission makes it possible to decrease the number of connectors, which allows optical coupling between the microcomputer and other parts of the system. The system provides the user with computer-aided execution of experiments, including synthesis of potential waveforms and collection and development of responses. The performance of the hardware system is demostrated by its application in determining cadmium at the ng 1^-1 level in a solution of Suprapur sulphuric acid by background-corrected anodic stripping voltammetry with a deposition time of 180 s and a scan rate of 9 V s^-1.     

Volta potential at metal-solid salt interface and real potentials of ions in solid electrolytes

Experimental conditions and results of investigations of Volta potentials of metal-solidelectrolyte and solid electrolyte-aqueous electrolyte solution by means of the dynamic condenser method are presented. These investigations were made for silver-silver halides and silver-silver nitrate as well as for cadmium-cadmium halide systems. On the basis of measured Volta potentials the real potentials of ions in these solid electrolytes are calculated. These real potentials are the ionic components of the crystalline lattice energy in the sense of the Gibbs energy.     

Imperfections in the aqueous lattice of clathrates,as detected by electron trapping

X-ray analysis has been used to elucidate the structure of hydrates, especially of aqueous clathrates, but it has not given information on imperfections occuring in crystals. Other methods, sensitive to the disturbance of structural periodicity, have to be applied to detect and identify the defects. Pulse radiolysis shows identical, intense transient spectra in a group of hydrates which exhibit certain common features. The spectrum ( _max = 620 nm) is tentatively ascribed to the electron trapped in a single water molecule vacancy in the aqueous moiety of the crystal. The pre-existing specific defect is formed during the crystallization process. The optical absorption spectrum is similar to the hydrated electron spectrum in liquid water or aqueous solutions. The nature of the traps is deduced from the known structure of clathrates, in which small anions substitute for one water molecule and may be displaced. Among investigated salt hydrates, amine hydrates and true clathrate hydrates, not all compounds show the ability to trap electrons. The present paper discusses the conditions for the occurrence of water molecule vacancies in the aqueous moiety of the clathrate and the general aspects of the observed phenomenon. A need to investigate imperfections by other methods is also stressed, although such alternatives are not yet available.     

Some aspects of the electron impact induced fragmentation of diastereoisomeric thymidine cyclic 3′,5′-phosphoranilidothioates

The similarities between the electron impact induced fragmentation of diastereoisomeric 4-methyl-2-thio-2 amino-1,3,2-dioxaphosphorinanes and thymidine cyclic 3′,5′-phosphoranilidothioates are discussed.