Extraction and coordination studies of the unexplored bifunctional ligand carbamoyl methyl sulfoxide (CMSO) with uranium(VI) and cerium(III) nitrates. Synthesis and structures of [UO2(NO3)(2)((PhSOCH2CONBu2)-Bu-i)] and [Ce(NO3)(3)(PhSOCH2CONBu2)(2)]

The bifunctional carbamoyl methyl sulfoxide ligands, PhCH2SOCH2CONHPh (L-1), PhCH2SOCH2CONHCH2Ph (L-2), (PhSOCH2CONPr2)-Pr-i (L-3), PhSOCH2CONBu2 (L-4), (PhSOCH2CONBu2)-Bu-i (L-5) and PhSOCH2CON(C8H17)(2) (L-6) have been synthesized and characterized by spectroscopic methods. The selected coordination chemistry of L-1, L-3, L-4 and L-5 with [UO2(NO3)(2)] and [Ce(NO3)(3)] has been evaluated. The structures of the compounds [UO2(NO3)(2)((PhSOCH2CONBu2)-Bu-i)] (10) and [Ce(NO3)(3)(PhSOCH2CONBu2)(2)] (12) have been determined by single crystal X-ray diffraction methods. Preliminary extraction studies of ligand L-6 with U(VI), Pu(IV) and Am(III) in tracer level showed an appreciable extraction for U(VI) and Pu(IV) in up to 10 M HNO3 but not for Am(III). Thermal studies on compounds 8 and 10 in air revealed that the ligands can be destroyed completely on incineration. The electron spray mass spectra of compounds 8 and 10 in acetone show that extensive ligand distribution reactions occur in solution to give a mixture of products with ligand to metal ratios of 1 : 1 and 2 : 1. However, 10 retains its solid state structure in CH2Cl2.

Coordination and extraction studies of an unexplored bi-functional ligand, carbamoyl methyl pyrazole (CMPz) with uranium(VI), lanthanum(III) and cerium(III) nitrates

The bi-functional carbamoyl methyl pyrazole ligands, C5H7N2CH2CONBu2 (L-1), (C5H7N2CH2CONBu2)-Bu-i (L-2), C3H3N2CH2CONBu2 (L-3), (C3H3N2CH2CONBu2)-Bu-i (L-4) and C5H7N2CH2CON(C8H17)(2) (L-5) were synthesized and characterized by spectroscopic and elemental analysis methods. The selected coordination chemistry of L-1 to L-4 with [UO2(NO3)(2)center dot 6H(2)O], [La(NO3)(3)center dot 6H(2)O] and [Ce(NO3)(3)center dot 6H(2)O] has been evaluated. Structures for the compounds [UO2(NO3)(2) C5H7N2CH2CONBu2] (6) [UO2(NO3)(2) (C5H7N2CHCONBu2)-Bu-i] (7) and [Ce(NO3)(3){C(3)H(3)N(2)CH(2)CON(i)Bu2}(2)] (11) have been determined by single crystal X-ray diffraction methods. Preliminary extraction studies of the ligand L-5 with U(VI) and Pu(IV) in tracer level showed an appreciable extraction for U(VI) and Pu(TV) up to 10 M HNO3 but not for Am(III). Thermal studies of the compounds 6 and 7 in air revealed that the ligands can be destroyed completely on incineration. (c) 2007 Elsevier Ltd. All rights reserved.

Experimental design and batch experiments for optimization of Cr(VI) removal from aqueous solutions by hydrous cerium oxide nanoparticles

Hydrous cerium oxide (HCO) was synthesized by intercalation of solutions of cerium(III) nitrate and sodium hydroxide and evaluated as an adsorbent for the removal of hexavalent chromium from aqueous solutions. Simple batch experiments and a 2⁵ factorial experimental design were employed to screen the variables affecting Cr(VI) removal efficiency. The effects of the process variables; solution pH, initial Cr(VI) concentration, temperature, adsorbent dose and ionic strength were examined. Using the experimental results, a linear mathematical model representing the influence of the different variables and their interactions was obtained. Analysis of variance (ANOVA) demonstrated that Cr(VI) adsorption significantly increases with decreased solution pH, initial concentration and amount of adsorbent used (dose), but slightly decreased with an increase in temperature and ionic strength. The optimization study indicates 99% as the maximum removal at pH 2, 20 °C, 1.923 mM of metal concentration and a sorbent dose of 4 g/dm³. At these optimal conditions, Langmuir, Freundlich and Redlich–Peterson isotherm models were obtained. The maximum adsorption capacity of Cr(VI) adsorbed by HCO was 0.828 mmol/g, calculated by the Langmuir isotherm model. Desorption of chromium indicated that the HCO adsorbent can be regenerated using NaOH solution 0.1 M (up to 85%). The adsorption interactions between the surface sites of HCO and the Cr(VI) ions were found to be a combined effect of both anion exchange and surface complexation with the formation of an inner-sphere complex.

Persistent luminescence of SrAl2O4:Ce(III), Dy, Eu nanotubes, nanowires and core-shells for people with disabilities: nano-emergency

Este estudo transversal está focado na propriedade de luminescência persistente do aluminato de estrôncio co-dopado com cério (III), disprósio (III) e európio (II), SrAl2O4:Ce3+, Dy3+, Eu2+, em sistemas de sinalização de áreas de risco e emergências para pessoas com deficiências. Na área da ciência e engenharia dos materiais, foram desenvolvidos novos materiais com características nanométricas, nanotubos, nanoarames e nanobastões luminescentes de SrAl2O4:Ce3+, Dy3+, Eu2+ para aplicações na área da reabilitação e acessibilidade de pessoas com deficiências. Os nanotubos foram obtidos a partir de micro- e nano-partículas precursoras sintetizadas por reacção do estado-sólido e tratamento térmico de recozedura (1273-1473 K). Os nanoarames e nanobastões foram preparados por moagem, sonificação e recozedura (373 K). Novas nanocápsulas de aluminatos luminescentes dopados com cério (III) e encapsulados com TiO2 foram criadas de modo a obter-se materiais multifuncionais, designadamente com acção fotocatalítica antimicrobiana, antibacteriana e resistência à água. Tais aluminatos podem ser amplamente aplicados como superfícies higiénicas, auto-limpantes, em biomateriais, no domínio de medicamentos antibióticos, na formulação de vacinas, e com ênfase à aplicação em cerâmicas fotoluminescentes. As metodologias de obtenção de tais nanoestruturas de aluminato de estrôncio dopado com cério (III) e do seu encapsulamento, desenvolvidas no âmbito desta tese, são aplicáveis a diversos aluminatos dopados com outros iões lantanídeos (Ln consiste em La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Tm ou Lu) com a fórmula M(1-x-y)N2O4:Cex, Lny, onde M é Be, Mg, Ca, Sr ou Ba. Na área da oftalmologia, foi desenvolvido um equipamento médico para o diagnóstico de biofuncionalidade das células retinais fotoreceptoras, e como suporte à telemedicina oftalmológica. Este equipamento foi utilizado para realizar testes de visão cromática FM100HUE em fundo branco/preto para a personalização de materiais luminescentes. Os resultados demonstraram uma biofuncionalidade celular à visibilidade fotópica das cores em fundo preto superior no grupo de tratamento, composto por pessoas com retinopatia diabética (n=38), em comparação ao grupo de referência (n=38). Estes resultados sugerem a recomendação de materiais com fotoluminescência persistente (λem=485-555 nm), incluindo SrAl2O4:Ce3+, Dy3+, Eu2+, para o referido grupo de tratamento, em sinalização de emergência e em ambientes de baixa iluminação. Na área da arquitectura, foi proposta uma nova aplicação dos referidos nanomateriais luminescentes à base de SrAl2O4:Ce3+, Dy3+, Eu2+ em cerâmica de revestimento, tendo em vista a sua boa visibilidade e uso por pessoas com deficiências. Novos pavimentos, cerâmicos, fotoluminescentes, foram desenhados com propriedades multisensoriais (contraste táctil, sonoro e visual) e antimicrobianas, para pessoas portadoras de deficiências utilizarem, no escuro, com a prioridade de salvar vidas em emergências. Tais pisos, com relevos, podem ser combinados de modo a compor um sistema exclusivo de sinalização fotoluminescente multisensorial que possibilita a rápida evacuação mediante o uso de auxílios de mobilidade (e.g. bengala, cadeira de rodas, andadores, muletas). A solução integrada de tais inovações que potencializa a propriedade de luminescência persistente de SrAl2O4:Ce3+, Dy3+, Eu2+ de modo acessível para as pessoas com deficiências, pode contribuir para salvar vidas, no escuro, em emergências.

Recognition of double helical DNA by purine oligonucleotides via triple helix formation

Oligonucleotide-directed triple helix formation is one of the most versatile methods for the sequence specific recognition of double helical DNA. Chapter 2 describes affinity cleaving experiments carried out to assess the recognition potential for purine-rich oligonucleotides via the formation of triple helices. Purine-rich oligodeoxyribonucleotides were shown to bind specifically to purine tracts of double helical DNA in the major groove antiparallel to the purine strand of the duplex. Specificity was derived from the formation of reverse Hoogsteen G•GC, A•AT and T•AT triplets and binding was limited to mostly purine tracts. This triple helical structure was stabilized by multivalent cations, destabilized by high concentrations of monovalent cations and was insensitive to pH. A single mismatched base triplet was shown to destabilize a 15 mer triple helix by 1.0 kcal/mole at 25°C. In addition, stability appeared to be correlated to the number of G•GC triplets formed in the triple helix. This structure provides an additional framework as a basis for the design of new sequence specific DNA binding molecules.

In work described in Chapter 3, the triplet specificities and required strand orientations of two classes of DNA triple helices were combined to target double helical sequences containing all four base pairs by alternate strand triple helix formation. This allowed for the use of oligonucleotides containing only natural 3'-5' phosphodiester linkages to simultaneously bind both strands of double helical DNA in the major groove. The stabilities and structures of these alternate strand triple helices depended on whether the binding site sequence was 5'-(purine)_m (pyrimidine)_n-3' or 5'- (pyrimidine)_m (purine)_n-3'.

In Chapter 4, the ability of oligonucleotide-cerium(III) chelates to direct the transesterfication of RNA was investigated. Procedures were developed for the modification of DNA and RNA oligonucleotides with a hexadentate Schiff-base macrocyclic cerium(III) complex. In addition, oligoribonucleotides modified by covalent attachment of the metal complex through two different linker structures were prepared. The ability of these structures to direct transesterification to specific RNA phosphodiesters was assessed by gel electrophoresis. No reproducible cleavage of the RNA strand consistent with transesterification could be detected in any of these experiments.

Hydrolysis of adenosine monophosphate and guanosine monophosphate by lanthanides

The hydrolysis of adenosine-5'-monophosphate(5'-AMP) and guanosine-5'-monophosphate(5'-GMP) by lanthanides was investigated. 5'-AMP and 5'-GMP was efficiently hydrolyzed by cerium(III) chloride under air at pH 9 and 37 degrees C, and other lanthanides (III) showed less efficiency at the same condition. The hydrolysis rate of 5'-AMP by cerium was greater than that of 5'-GMP. UV spectra showed that Ce(III) was oxidized to Ce(IV) in the reaction mixture. The active species for the hydrolysis of 5'-AMP and 5'-GMP was ascribed to the Ce(IV) hydroxide cluster in the reaction mixture.

Efficient cleavage of ribonucleoside 3',5'-cyclic phosphates and deoxyribonucleoside 3',5'-cyclic phosphate by lanthanides

The cleavage of 3',5'-cAMP, 3',5'-cGMP and 3',5'-dcAMP by lanthanides has been investigated by HPLC and H-1 NMR. Rapid cleavage of cAMP, cGMP and dcAMP by Ce(III) under air at pH 8 and 37 degrees C has been observed. Regioselective cleavage of P-O(5') bond in cAMP, cGMP and dc;aMP tu give the corresponding 3'-AMP, 3'-GMP and 3'-dAMP by lanthanide chlorides has been achieved, and 3'-AMP and 3'-GMP are cleaved to adenosine(A) and guanosine(CT) more slowly, respectively, The notable difference in reactivity between Ce(III) and the other lanthanide ions under air has also been studied. The cleavage is enhanced with the increase in the molar fraction of Ce(IV). The fast cleavage of cAMP by Ce(III) under air at pH 8 is ascribed to the resultant Ce(IV) in the reaction mixture.

Sr2CeO4: Electronic and structural properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, spectral, and anti-microbial studies of thioiminium iodides and amine hydrochlorides

To avoid the undesired deprotonation during the addition of organolithium and organomagnesium reagents to ketones, the thioiminium salts, easily prepared from lactams and amides are converted into 2,2-disubstituted and 2-monosubstituted amines by reaction with simple nucleophiles such as organocerium and organocopper reagents. The reaction of thioiminium iodides with organocerium reagents derived by transmetalation of corresponding lithium reagents with anhydrous cerium(III) chloride has been investigated. These thioiminium iodides act as good electrophiles and accept alkylceriums towards bisaddition. The newly synthesized amines have been characterized by 1H and 13C NMR, IR and mass spectra. The amines have been converted into their hydrochlorides and characterized by COSY. These hydrochlorides have been subjected to antimicrobial screening with clinically isolated microorganisms, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi and Candida albicans. The hydrochlorides show quite good activity against these bacteria and fungus.

Recovery of palladium from a spent automobile catalyst leaching solution by a thiodiglycolamide derivative

In the sequence of previous research on the development of novel liquid-liquid amidetype compounds to efficiently and selectively extract platinum-group metals (PGMs) from concentrated hydrochloric acid media, a specific thiodiglycolamide derivative – N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) – has been applied for the recovery of palladium(II) from a spent automobile catalyst leaching solution, containing palladium(II) and rhodium(III) as PGMs. The results obtained are rather promising, since the DMDCHTDGA behavior towards the two PGMs is similar to that observed for hydrochloric acid aqueous media studied before, simulating the real leaching phases. Within eleven metal elements co-existing in solution, the majority in high fold-excesses, only aluminum(III) and cerium(III) interfere in the palladium(II) liquid-liquid extraction process, requiring further optimization.

Rearrangements in the cerium(IV) and manganese(III) oxidations of substituted naphthalenes and the nih shift mechanism

Ceric ammonium sulphate oxidation of 1- and 1,4- disubstituted naphthalenes gives 2- and/or 2,3- disubstituted 1,4- naphthoquinones through migration of substituents (D, Br, Ph). Similar rearrangements are also observed in the manganese(III) oxidation and also in the anodic oxidation of these substrates. The results are consistent with the proposal that these oxidations go through the formation of radical cation followed by reaction with H2O and further oxidation of the radical to the carbocationic intermediate on the way to the corresponding 1,4-naphthoquinone. Oxidation of 1,4-diphenylnaphthalene gives 2,3-diphenyl-1,4-naphthoquinone or 4-hydroxy- 2,4- diphenyl - 1(4)R - naphthalenone. The results are in accordance with the conclusion that such rearrangements do not require prior formation of arene oxide intermediates, originally proposed for the NM shift mechanism.

The separation of Cerium(IV) from nitric acid solutions containing Thorium(IV) and Lanthanides(III) using pure [C(8)mim]PF6 as extracting phase

The extraction behavior of Ce(IV) along with Th(IV) and Ln(III) (Ln = Ce, Gd, Yb) nitrate by pure ionic liquid, [C(8)mim]PF6, was investigated. [C(8)mim]PF6 alone showed good extraction ability for Ce(IV), while it was slight for Th(IV) and negligible for Ln(III). The extraction behavior of Ce(IV) by [C(8)mim]PF6 was particularly studied, and the most probable extraction mechanism proposed was the anion exchange mechanism. Moreover, the stripping of Ce(IV) from IL phase was also investigated. The Ce(IV) in IL phase can be quantitatively recovered by water.