No abstract

The reactions between trinuclear gold complex tppmAu(3)Cl(3) (tppm = tris(diphenylphosphino)methane), arylacetylenes HC(2)C(6)H(4)X and Cu(+) under basic conditions result in formation of the heterometallic complexes [tppm(AuC(2)C(6)H(4)X)(3)Cu](+), X = H (1), COOMe (2), CN (3), OMe (4), NH(2) (5). These compounds belong to one structural motif and consist of the heterometallic {(AuC(2)C(6)H(4)X)(3)Cu} core stabilized by the tridentate phosphine. Compounds 1-5 were characterized by polynuclear NMR and IR spectroscopy, ESI-MS and single-crystal X-ray analysis. Luminescence properties of these complexes have been studied and revealed a substantial red shift of the emission maxima with the increase in the electron donicity of the alkynyl ligands substituents in the 550-680 nm range. The theoretical calculations of the electronic structures showed that variations of the substituents on the alkynyl ligands display very little effect on the molecular structural parameters but show appreciable influence on the orbital energies and luminescence characteristics of the compounds under study.

Leishmaniasis is a vectorborne disease transmitted to human and other mammalian hosts by sand fly bite. In the present study, we show that immunization with Leishmania mexicana promastigote secretory gel (PSG) or with a chemically defined synthetic glycovaccine containing the glycans found in L. mexicana PSG can provide significant protection against challenge by the bite of infected sand flies. Only the glycan from L. mexicana was protective; those from other species did not protect against L. mexicana infection. Furthermore, neither PSG nor the glycovaccine protected against artificial needle challenge, which is traditionally used in antileishmanial vaccine development. Conversely, an antigen preparation that was effective against needle challenge offered no protection against sand fly bite. These findings provide a new target for Leishmania vaccine development and demonstrate the critical role that the vector plays in the evaluation of candidate vaccines for leishmaniasis and other vectorborne diseases.

No abstract

During the last decades, rhodium complexes have attracted the attention of researchers as they are efficient catalysts of diverse, including practically significant, reactions in organic synthesis (methanol carbonylation, alkene and alkyne hydrogenation, and alkene hydroformylation). Among rhodium compounds that deserve attention, special emphasis should be put on rhodium(I) carbonyl complexes, which are often used as precursors of catalytic systems and function as active intermediates in catalytic cycles. The sensitivity of the carbonyl ligand to the electronic state of the central atom and particularly characteristic stretching vibrations of the carbonyl ligand make it possible to use the ν ( CO ) stretching frequency as a source of useful information on the donor-acceptor interactions in the coordination sphere and on the mutual ligand effects.In a previous publication [1], the spectral (IR and NMR) characteristics of the carbonyl groups in rhodium(I) carbonyl carboxylate complexes have been determined and some correlations between these characteristics and the electronegativity of the substituent R in the carboxylate ligand were found. It was also found that transition from dicarbonyl (per one rhodium atom) com-, is accompanied by substantial changes in the spectroscopic parameters of the carbonyl groups. These observations were interpreted [1] using the intuitive views on ligand effect transfer through the central atom. The authors of [1] also paid attention to the fact that the IR spectra of the binuclear carbonyl carboxylate complexes differ appreciably in the carbonyl stretching region (the intensity ratio of the observed absorption bands) from the spectrum of the chloride analog [ Rh ( µ -Cl )( CO ) 2 ] 2 . This difference was tentatively attributed to the change in the dihedral angle ( q ) formed by the coordination planes of the rhodium atoms on passing from the carboxylate complexes to the complex with monoatomic chloride bridges. In view of a successful experience of DFT description of the structure and vibrational spectra of the mononuclear rhodium(I) carbonyl complexes [2-4], we performed such quantum-chemical calculations for interpreting the experimental data concerning binuclear rhodium(I) complexes, [ Rh ( µ -Cl )( CO ) 2 ] 2 and [ Rh ( µ -RCOO )( CO ) 2 ] 2 (R = H, CH 3 , CF 3 ). The study aimed at answering the following questions:-to what extent the results of quantum-chemical calculations can reproduce the set of experimental structural and spectral parameters of each compound separately;-whether the calculation results reported previously [1] reflect the correlations between these parameters and what characteristics of the electronic structure of the complex (atomic charges, orbital populations, bond orders) may by considered responsible for these correlations;-whether the calculations confirm the assumption made previously [1] that the intensity ratio of the ν ( CO ) stretches in the IR spectra of binuclear complexes correlates with the value of the dihedral angle between the Rh ( CO ) 2 ...