Stereo- and regioselective synthesis of β-amino-β-tetrazolylvinylphosphonates

Addition of 5-substituted tetrazoles to dimethyl [(N,N-diisopropylamino)ethynyl]phosphonate proceeds regio- and stereoselectively to yield (Z)-[2-diisopropylamino-2-(tetrazolyl)vinyl]phosphonic acid dimethyl esters. The Z-configuration of the products was confirmed by ¹Н NMR spectroscopy and single-crystal X-ray diffraction. The reactions occur via nucleophilic attack of tetrazole involving predominantly the N-1 atom of the tetrazole ring.     

A solution to an inverse height and level characteristics problem

Given two sequences α and β of positive integers, it is shown that there exists a matrix with level characteristic α and height characteristic β if and only if β strictly majorizes α when reordered in non-increasing order. This generalizes a recently proven result for the case of matrices with simple singular vertices.     

Effect of the Counter Anion and Solvate on the Structure,Stability and Spectral Properties of a Ruthenium(II) Complex Containing Group 15 Donors and 2,2′ :6′,2′′-terpyridine

Ruthenium complexes [Ru(κ³−tpy)(AsPh₃)₂C1]PF₆ · 0.42H₂O (tpy =2,2′:6′,2′′-terpyridine) (1) and a new crystal form of [Ru(κ³−tpy)(AsPh₃)₂Cl]BF₄ (2), which crystallized without water solvate, and their comparative studies on spectral, structure and stability aspects are reported. The complexes have been characterized by elemental analyses, FAB-MS, i.r., ¹H n.m.r. and electronic spectral studies. In these complexes weak C—H···Fπ and face-to-face π–π interactions lead to a single helical motif while, C—H···FX (X=F, Cl) interactions result in linear chains. Various studies on the stability of the complexes suggested that the compound containing the counter anion PF₆^- is more stable than the other containing BF₄^- as the counterpart.     

Specific absorption parameters for uranium octoxide and dioxide applicable to the ICRP Publication 66 respiratory tract model

Literature data from in vivo chest measurements and urinary excretion rates of individuals exposed to U₃O₈ and UO₂ were used to compare the results predicted by different models with empirical observations in humans. As a result the use of the respiratory tract model proposed in ICRP Publication 66 with its default absorption parameters underestimates urinary excretion of inhaled U₃O₈ and UO₂. The new respiratory tract model also overpredicts the Fecal/Urine activity ratio, independently of the systemic model. For U₃O₈ and UO₂ the choice of systemic model has very little influence on the predicted urinary excretion of inhaled compounds. On the other way, the choice of the respiratory tract model does influence the predicted urinary excretion significantly. In this work specific absorption parameters for U₃O₈ and UO₂ were derived to be used in the respiratory tract model proposed in ICRP Publication 66. The predicted biokinetics of these compounds were compared with those derived for Type M and Type S compounds of uranium.     

Mixed sorbents and their use in continuous flow analysis

The new approach to enhancing the selectivity of sorption separation of metal ions was suggested. The approach is based on using mixed sorbents, which may be obtained, e.g. by simultaneous immobilization of complexing reagents on silica gel and reverse-phase silica gel (C₁₆, Ph). The methods are developed for the simultaneous determination of two (Co-Fe, Co-Zn, Al-Mn) or three (Al, Mn and Fe) elements in the concentration range 2.10^–6–7.10^–4 M with the performance of 21–36 samples per hour.     

Arene ruthenium complexes incorporating immine/azine hybrid-chelating N-N donor ligands: synthetic, spectral, structural aspects and DFT studies

New series of mono and binuclear arene ruthenium complexes [{(η⁶-arene)RuCl(L)}]⁺ and [{(η⁶-arene)RuCl}₂(μ-L)₂]²⁺ (arene=benzene, p-cymene or hexamethylbenzene), {L=pyridine-2-carbaldehyde azine (paa), p-phenylene-bis(picoline)-aldimine (pbp) and p-bi-phenylene-bis(picoline)-aldimine (bbp)} are reported. The complexes have been fully characterized and molecular structure of the representative mononuclear complex [(η⁶-C₆Me₆)RuCl(paa)]BF₄ (1), binuclear complexes [{(η⁶-C₁₀H₁₄)RuCl}₂(μ-paa)](BF₄)₂ (3) and [{(η⁶-C₁₀H₁₄)RuCl}₂(μ-pbp)](BF₄)₂ (6) have been determined by single crystal X-ray diffraction analyses. Single crystal X-ray structure determination revealed that in the binuclear complexes the [(η⁶-C₁₀H₁₄)RuCl]⁺ units are trans disposed. Further, the crystal packing in the complexes 1, 3 and 6 is stabilized by C-H?X type (X=Cl, F) inter, intramolecular hydrogen bonding and π-π stacking (3). To explore the ambiguous nature of the bonding between pyridine-2-carbaldehyde azine (paa) with ruthenium containing units [(η⁶-arene)RuCl]⁺, DFT/B3LYP calculations have been performed on the complexes [(η⁶-arene)RuCl(paa)]⁺ (arene=C₆H₆, I; C₆Me₆, II; C₁₀H₁₄, III).     

Thermogravimetric and calorimetric evaluation of babassu biodiesel obtained by the methanol route

The growing petroleum deficit requires the development of alternative fuel sources. Biodiesel is a good alternative, as it is a biodegradable and renewable product, which obeys the carbon cycle. In this work, the biodiesel from babassu was synthesized using the methanol route, and characterized by physico-chemical analyses in order to make able the investigated biodiesel to fulfill with its properties the requirements of Brazilian National Agency for Petroleum, Natural Gas and Biofuel (ANP). Besides gas chromatography, IR spectroscopy experiments and thermoanalytical measurements in air and in nitrogen were done to determine the main thermal decomposition processes and calorimetric events. The evaporation temperature of babassu biodiesel was similar in both atmospheres, started around 52 in air and around 60°C in nitrogen.     

Examination of novel zinc-binding groups for use in matrix metalloproteinase inhibitors

The tetrahedral zinc complex [(Tp(Ph,Me))ZnOH] (Tp(Ph,Me) = hydrotris(3,5-phenylmethylpyrazolyl)borate) was combined with 1-hydroxy-2(1H)-pyridinone, 3-hydroxy-2(1H)-pyridinone, 3-hydroxy-1-methyl-2(1H)-pyridinone, 3-hydroxy-1,2-dimethyl-4(1H)-pyridinone, 1-hydroxy-2(1H)-pyridinethione, and 3-hydroxy-2-methyl-4-pyrone to generate the complexes [(Tp(Ph,Me))Zn(ZBG)] (ZBG = zinc-binding group). These complexes were synthesized to explore the coordination geometry of potential novel zinc-binding groups for use in matrix metalloproteinase (MMP) inhibitors. The solid-state structures of all six metal complexes were determined by X-ray crystallography. These structures combined with IR and (1)H NMR data demonstrate that these ZBGs bind in a strong, bidentate fashion to the zinc(II) ion. Modeling studies indicate that these ZBGs can easily fit into the MMP active site. In an effort to develop more effective inhibitors of MMPs, this work has revealed molecular-level interactions for six potential new ZBGs.