Geraldo M. de Lima

Catalysts of Cu(II) and Co(II) ions adsorbed in chitosan used in transesterification of soy bean and babassu oils - a new route for biodiesel syntheses.

Catalysts of Cu(II) and Co(II) adsorbed in chitosan was used in transesterification of soy bean and babassu oils. The catalysts were characterized by infrared, atomic absorption and TG, and biodiesels was characterized by infrared, NMR, CG, TG, physic chemistry analysis. The maximum adsorption values found for copper and cobalt cations were 1.584 and 1.260mgg(-1), respectively, in 180min. However, conversion of oils in biodiesel was better when used Co(II) adsorbed in chitosan.

The influence of cation upon the supramolecular aggregation patterns of dithiocarbamate anions functionalised with hydrogen bonding capacity—the prevalence of charge-assisted O–H⋯S interactions

A range of supramolecular architectures is found in the title dithiocarbamate salts, each with hydrogen bonding functionality in the form of aτ least one hydroxyl group. A common feature in the crystal packing is the prevalence of charge-assisted O–H⋯S hydrogen bonding. In [NH4][S2CN(CH2CH2OH)2] (1), a 3-D network is found mediated by cooperative O–H⋯S, N–H⋯O and N–H⋯S hydrogen bonding. Reducing the hydrogen bonding functionality by replacing the ammonium cation in (1) by the 4-aza-1-azoniabicyclo(2.2.2)octanium cation to give [DABCO-H][S2CN(CH2CH2OH)2] (2), results in a 2-D array. Further reduction of the hydrogen bonding functionality, this time by substituting a CH2CH2OH with an alkyl group to give [DABCO-H][S2CN(CH2CH2OH)CH3] (3) and [DABCO-H][S2CN(CH2CH2OH)CH2CH3] (4) allows for the formation of 1-D supramolecular chains. The introduction of alkali metal cations rather than protic cations removes the possibility of the hydroxyl-O participating in hydrogen bonding interactions as these now coordinate the alkali metal. In the sodium trihydrate, Na[S2CN(CH2CH2OH)2]·3H2O (5), O–H⋯O hydrogen bonds are found along with charge-assisted O–H⋯S contacts so that a 3-D network results. Substituting a CH2CH2OH group with a n-propyl group gives Na[S2CN(CH2CH2OH)CH2CH2CH3]·2H2O (6) and yields a 2-D array. For the anhydrous K[S2CN(CH2CH2OH)2] (7) and Cs[S2CN(CH2CH2OH)2] (8) salts, the crystal packing is dominated by charge-assisted O–H⋯S hydrogen bonding giving 3-D network structures. The systematic analysis of the crystal packing patterns of these salts reveals the importance of charge-assisted O–H⋯S hydrogen bonding in stabilising these crystal structures.

Design, structural and spectroscopic elucidation, and the in vitro biological activities of new diorganotin dithiocarbamates.

The reaction of 2,2-dimethoxy-N-methylethyllamine or 2-methyl-1,3-dioxolane with CS(2) in alkaline media produced two novel dithiocarbamate salts. Subsequent reactions with organotin halides yielded six new complexes: [SnMe(2){S(2)CNR(R(1))(2)}(2)] (1), [Sn(n-Bu)(2){S(2)CNR(R(1))(2)}(2)] (2), [SnPh(2){S(2)CNR(R(1))(2)}(2)] (3), [SnMe(2){S(2)CNR(R(2))(2)}(2)] (4), [Sn(n-Bu)(2){S(2)CNR(R(2))(2)}(2)] (5), [SnPh(2){S(2)CNR(R(2))(2)}(2)] (6), where R = methyl, R(1) = CH(2)CH(OMe)(2), and R(2) = 2-methyl-1,3-dioxolane. All compounds were identified in terms of infrared, (1)H and (13)C NMR, and the complexes were also characterized using (119)Sn NMR, (119)Sn Mössbauer and X-ray crystallography. The biological activity of all derivatives has been screened in terms of IC(90) and IC(50) against Aspergillus flavus, Aspergillus niger, Aspergillus parasiticus, Penicillium citrinum, Curvularia senegalensis, Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Streptococcus sanguinis, Escherichia coli, Citrobacter freundii, Salmonella typhimurium, and Pseudomonas aeruginosa and the results correlated well with a performed study of structure-activity relationship (SAR). Complexes (3), (5) and (6) displayed the best IC(90) and IC(50) in the presence of the fungi, greater than that of miconazole, used as control drug.

Tin, palladium and platinum derivatives of 1,1′-bis(diphenylphosphine)ferrocene. Crystal and molecular structures of 1,1′- bis-(diphenylphosphine)ferrocenedichloropalladium(II) and of 1,1′-bis(diphenylphosphine)ferrocenedichloroplatinum(II)

SummaryTen derivatives of 1,1′-bis(diphenylphosphine)ferrocene (BDPF) are described in this paper. The first three, [BDPF·SnCl4] (1), [BDPF·MeSnCl3] (2) and [BDPF·PhSnCl3] (3), present the two phosphorus atoms of the ligand directly bonded to a Sn centre. Two others, [BDPF-PdCl2 (4) and [BDPF·PtCl2] (5), similarly have the ligand BDPF acting as a bidentate species towards a transition metal. The crystal and molecular structures of (4) and (5) are presented here. Two other BDPF complexes were obtained with Pd and Pt, with the transition metals in the zerovalent state, namely [Pd(BDPF)2] (6) and [Pt(BDPF)2] (7). Finally, three trimetallic complexes are also described; [BDPF·Pd(μ-Cl)2SnCl2] (8), [BDPF· Pt(μ-Cl)2SnCl2] (9) and [BDPF·PdClSnCl3] (10).

Thermal decomposition of sulfur-containing organotin molecular precursors to produce phase-pure SnS

The present work reports a simple route to prepare tin(II) sulfide semiconductor nanometric particles by thermal decomposition in air of the easily prepared organotin sulfur-containing precursors R4Sn4S6 [R = Me, Bun and Ph]. Thermogravimetric (TG) analyses showed that Me and Bun derivatives decompose in a single sharp step at relatively low temperatures to produce the pure SnS phase, which was confirmed by powder X-ray diffraction (XRD). Temperature programmed decomposition-mass spectrometry (TPD/MS) experiments suggested that the decomposition occurs ia reductive elimination steps involving the –R and –S groups. The ring structured R6Sn3S3 [R = Me, Bun, But and Ph] compounds were also studied. However, during thermal decomposition in nitrogen or air tin is partially lost to the gas phase due to sublimation, leaving Sn or SnO, with only traces of SnS.

2-Hydroxyacetophenone arylhydrazones. Supramolecular arrangements based on C–H · · · O(H), CH · · · O(NO), N–H · · · O(H), N–H · · · O(NO), C–H · · · π or π · · · π interactions

Abstract Crystal structures, NMR and IR spectra and EI-MS+ of 2-hydroxyacetophenone arylhydrazones, 2-HOC6H4C(Me) = NNHC6H4Y (1: Y = 2-O2N, 3-O2N, 4-O2N, 4-Me, 4-MeO, H and 4-I) are reported. Two polymorphs of (1: Y = 2-O2N), triclinic and orthorhombic forms, have been identified. While strong intramolecular O–H · · · N(H) hydrogen bonds and layers of molecules are found for all solid 1, supramolecular arrangements of individual members are various and are derived from different combinations of intermolecular interactions, which include C–H · · · O(H), C–H · · · O(NO), N–H · · · O(H), N–H · · · O(NO) and C–H · · · π hydrogen bonds, as well as π · · · π stacking interactions. Intermolecular N–H · · · O hydrogen-bonds involving the phenolic OH group are present in (1: Y = H, 4-O2N, 4-Me, 4-MeO and 4-I), but are absent in ortho-and tri-(1: Y = 2-O2N) and (1: Y = 3-O2N). Instead, ortho-(1: Y = 2-O2N) exhibits intermolecular C–H · · · O(H) hydrogen bonds, while no intermolecular hydrogen bonds involving the OH group occur in either triclinic-(1: Y = 2-O2N) or (1: Y = 3-O2N). EI+-MS revealed the presence of oligomeric species, such as (nM + M′)+, where n is up to 4, and M′ = H, Na or K.

Antimony and chromium determination in Brazilian sugar cane spirit, cachaça, by electrothermal atomic absorption spectrometry using matrix matching calibration and ruthenium as permanent modifier

This work reports a method for the determination of antimony and chromium in Brazilian sugar cane spirit, cachaca, by electrothermal atomic absorption spectrometry (ET-AAS) employing matrix matching calibration and ruthenium, thermally deposited (500 µg), as permanent modifier. The best pyrolysis and atomisation temperatures were 600 °C and 1400 °C for antimony while for chromium it was 700 °C and 2500 °C, respectively. For chromium, the peak returned to the baseline after 15 s in the absence of any modifier, whilst using Ru as permanent modifier, the peak returned to the baseline in 5 s, showing high symmetry. The characteristic mass (mo) obtained for chromium was 2.4 pg without modifier and 2.5 pg with Ru permanent (recommended 8.0 pg). For antimony it was 43.4 pg and 24.6 pg without modifier and with Ru permanent, respectively (recommended 200 pg). Matrix matching calibration curves (aqueous solutions 40% v/v in ethanol) gave a value of r (linear regression coefficient) higher than 0.999 for the two analytes. For antimony, two samples of cachaca spiked with 30.0, 60.0 and 90.0 µg l−1 showed a range of recovery from 98.8% to 110.0%, while for chromium it was from 101.7% to 107.9%. The detection limits (k = 3, n = 10) were 43 pg for antimony and 2 pg for chromium. The results obtained from analysis of fifty-two samples of cachaca, from Alto Vale do Jequitinhonha, Minas Gerais State, Brazil, varied from non-detectable to 39.1 µg l−1 for antimony and the RSDs, (n = 3), from 2.87% to 11.10%. For chromium, the same samples showed results from 0.64 to 1.53 µg l−1 (RSDs from 0.04% to 11.76%).

Mössbauer studies of heterobimetallic and heterotrimetallic compounds containing iron and tin

A series of ferrocene derivatives was prepared and studied by57Fe and119Sn Mössbauer spectroscopy, as well as by other techniques such as NMR and IR spectroscopies. These complexes can be divided into three types: mercurated, organotin derivatives of ferrocene, and bi- and trimetallic derivatives of 1,1′-bis(diphenylphosphino)ferrocene. Iron did not show great variation in its Mössbauer parameters in the compounds, in spite of their diversity; tin, however, gave important Mössbauer data for the elucidation of bonding and structural features of the complexes.

Cyclization of N-alkyldithiocarbamates in alkaline media, a counter example of well-known chemistry – an experimental and theoretical study

In strong alkaline media, the reaction of 2-(tert-butylamino)ethanol (3: R = But) with CS2 at 0°C produced a cyclic dithiocarbamate, 3-tert-butylthiazolidine-2-thione (1: R = But), rather than alkaline metal or ammonium salts of [S2CN(But)CH2CH2OH]−. This is in contrast to isolation of stable alkaline metal or ammonium salts of [S2CN(R)CH2CH2OH]− (R = Me, Et, Pr, or CH2CH2OH) obtained in analogous reactions. The use of Ni(OAc)2, both as a source of Ni(II) and a weaker base, in a one-pot reaction with (3: R = But) and CS2, successfully gave the first reported metal complex of [S2CN(But)CH2CH2OH]−, namely [Ni{S2CN(But)CH2CH2OH}2] (2: R = But). Compounds 1 and 2 have been fully characterized by infrared and NMR spectroscopies, and by X-ray crystallography. DFT calculations on the cyclization and stabilities of [S2CN(R)CH2CH2OH]− (R = Pr and But) have been carried out.

Synthesis, characterization and biocidal activity of new organotin complexes of 2-(3-oxocyclohex-1-enyl)benzoic acid.

The reaction of 1,3-cyclohexadione with 2-aminobenzoic acid has produced the 2-(3-oxocyclohex-1-enyl)benzoic acid (HOBz). Subsequent reactions of the ligand with organotin chlorides led to [Me(2)Sn(OBz)O](2) (1), [Bu(2)Sn(OBz)O](2) (2), [Ph(2)Sn(OBz)O](2) (3), [Me(3)Sn(OBz)] (4), [Bu(3)Sn(OBz)] (5) and [Ph(3)Sn(OBz)] (6). All complexes have been fully characterized. In addition the structure of complexes (2) and (4) have been authenticated by X-ray crystallography. The biological activity of all derivatives has been screened against Cryptococcus neoformans and Candida albicans. In addition we have performed toxicological testes employing human kidney cell. The complexes (3), (5) and (6) displayed the best values of inhibition of the fungus growing, superior to ketoconazole. Compound (5) presented promising results in view of the antifungal and cytotoxicity assays.