Classical versus Jennings model for the ground state of H near a metallic surface

We show that, contrary to earlier reports, application of the one-parameter variational technique to the classical (image) model for H in front of an Al surface leads to energy shifts for the ground state which are very close to those obtained numerically with a more sophisticated model of the system.     

Spectrophotometric determination of tin(IV) by extraction of the ternary tin/iodide/5,7-dichloro-8-quinolinol complex

The characteristics of the ternary complexes formed by fluoride, bromide, iodide and thiocyanate with tin(IV) and 5,7-dichloro-8-quinolinol (HCQ) have been studied. A spectrophotometric method is proposed for the determination of tin(IV) (1–20 μg ml^?1), based on the extraction into chloroform of the tin/iodide/HCQ complex. Aluminium, bismuth and lead do not interfere, but antimony, copper, iron(III) and fluoride do. Copper and iron can be eliminated by preliminary extraction in the absence of iodide.     

Barreleneiridium(I) complexes. Crystal structures of [Ir(Me3TFB)(η6-C6H4Me2)]ClO4 and [Ir(TFB)(η5-PhNPh2)]BF4·CH2Cl2 (TFB = tetrafluorobenzobarrelene)

A new series of cationic areneiridium(I) complexes of formula [Ir(barrelene)(arene)]⁺ or [Ir(barrelene)(PhNRPh)]⁺ (R= Ph or H) have been synthesized from neutral iridium complexes of the type [IrY(barrelene)]_x (barrelene = Me₃TFB, Y = Cl or OMe (x = 2), Y = acac (x = 1); barrelene = TFB, Y = OMe (x = 2), Y = acac (x = 1)). The crystal structures of [Ir(Me₃TFB)(1,4-C₆H₄Me₂)]ClO₄ and [Ir(TFB)(PhNPh₂)]BF₄·CH₂Cl₂ have been determined by X-ray diffraction. They crystallize in the space groups Pbca and Pna2₁ respectively with lattice constants of 17.6947(11), 15.8072(10), 16.0019(11) Å and 9.8059(2), 20.8097(9), 14.3367(4) Å. Final R factors were 0.063 and 0.042 for the observed data. Both complexes show a staggered arrangement between the arene and the TFB moieties and deviation from planarity of the coordinated arene ligands. In the second complex the IrC and NC distances, the CNC angle, the type of arene puckering, and the spectroscopic data indicate a distortion of the coordinated arene towards a η⁵-coordinated iminocyclohexadienyl form.     

On <Emphasis Type="Italic">C</Emphasis><Superscript><Emphasis Type="Italic">r</Emphasis></Superscript>-closing for flows on orientable and non-orientable 2-manifolds

We provide an affirmative answer to the C ^r -Closing Lemma, r ≥ 2, for a large class of flows defined on every closed surface.     

Raman spectra and binding of CuII to purine nucleotides

Raman spectra of adenosine 5′-monophosphate, poly(rA), guanosine 5′-monophosphate and their Cu^II complexes have been obtained and analysed by referring to spectra of D-, ¹⁵N- and ¹³C-labelled nucleobases. The greatest spectral changes on attachment of Cu^II to these nucleotides are associated with changes in the five-membered ring and suggest that the metal binds preferentially to N-7 of nucleobases. However, in the Cu^II coordinated poly(rA) species, N-1 binding sites are also present to some extent, as deduced from the comparison of the Raman spectrum of the Cu-poly(rA) complex with that of the protonated polynucleotide. In the complexes of guanosine 5′-monophosphate with Cu^II, the guanine residue is located at the anti position with respect to the ribose moiety through the glycosidic bond. In all cases, strong changes are also recorded for characteristic bands of phosphate groups, indicating their participation as ligands surrounding Cu^II.