Infrared and Raman spectroscopic characterization of some organic substituted hybrid silicas.

Nine hybrid silicas bearing the organic substituent groups methyl, octyl, octadecyl, vinyl, phenyl, mercaptopropyl, isocyanatopropyl, chloropropyl and glycidoxypropyl were synthesized by an acid-catalyzed, hydrolytic sol-gel process. The resulting solid materials were characterized by their absorbance and attenuated total reflection (ATR) IR and Raman spectra. The latter technique proved to be particularly useful in the identification of the organic moieties in the hybrid silicas. The effect of the presence of the organic groups on the silica networks was also investigated - there were increases observed in both the SiOSi bond angles and bond lengths. Moreover, deconvolution of the IR-active antisymmetric SiOSi stretching bands permitted detection of the four- and six-membered siloxane rings present in the silicas. There proved to be a greater number of four-membered rings on the surfaces of the particles. Both IR and Raman spectroscopy proved to be invaluable in the characterization of these hybrid materials.

Glycosylation studies on conformationally restricted 3,5-O-(di-tert-butylsilylene)-D-galactofuranosyl trichloroacetimidate donors for 1,2-cis α-D-galactofuranosylation.

Conformationally restricted 3,5-O-di-tert-butylsilylene-D-galactofuranosyl trichloroacetimidate donors were synthesized from allyl α-D-galactofuranoside for the construction of 1,2-cis α-D-galactofuranosyl linkages. Glycosylation reactions were performed with several acceptors, including D-galactono-1,4-lactone, D-rhamnopyranosyl, and D-mannopyranosyl derivatives. The influence of the temperature and the reaction solvents was evaluated, as well as the 6-O-substitution pattern of the donor. The higher α-selectivities were obtained at -78 °C in diethyl ether as solvent. 6-O-Acetyl substitution on constrained donor increased the α-selectivity compared to the 6-O-benzyl substitution. Almost no selectivities were observed in the non-participating solvent CH(2)Cl(2). In contrast, ethereal solvents enhanced the α-selectivity suggesting a participating effect in the reaction intermediate.

Facile synthesis of per-O-tert-butyldimethylsilyl-beta-D-galactofuranose and efficient glycosylation via the galactofuranosyl iodide.

The synthesis of crystalline per-O-TBS-beta-D-galactofuranose (4beta) as a new precursor of D-Gal f units is described. Anomeric iodination by reaction with TMSI followed by in situ coupling with simple alcohols and a wide variety of glycosyl acceptors, in the absence of a promoter, was employed as a new efficient glycosylation method for the assembly of D-galactofuranosyl moieties with high beta-stereoselectivity. Under the mild conditions of this reaction labile protective groups, like acetals, and furanosyl linkages are preserved.

Nanoparticles of octakis[3-(3-amino-1,2,4-triazole)propyl]octasilsesquioxane as ligands for Cu(II), Ni(II), Cd(II), Zn(II), and Fe(III) in aqueous solution.

Nanoparticles of octakis[3-(3-amino-1,2,4-triazole)propyl]octasilsesquioxane (ATZ-SSQ) were tested as ligands for transition-metal ions in aqueous solution with a special attention to sorption isotherms, ligand-metal interaction, and determination of metal ions in natural waters. The adsorption potential of the material ATZ-SSQ was compared with related [3(3-amino-1,2,4-triazole)propyl]silica gel (ATZ-SG). The adsorption was performed using a batchwise process and both organofunctionalized surfaces showed the ability to adsorb the metal ions from aqueous solution. The Langmuir model was used to simulate the sorption isotherms. The results suggest that the sorption of these metals on ATZ-SSQ and ATZ-SG occurs mainly by surface complexation. The equilibrium condition is reached at time lower than 3 min for ATZ-SSQ, while for ATZ-SG is only reached at time of 25 min. The maximum metal ion uptake values for ATZ-SSQ were higher than the corresponding values achieved with the ATZ-SG. In order to obtain more information on the ligand-metal interaction of the complexes on the surface of the ATZ-SSQ nanomaterial, ESR study with various degrees of copper loadings was carried out. The ATZ-SSQ was tested for the determination (in flow using a column technique) of the metal ions present in natural waters.

Synthesis and photochemical properties of a bis(n-Hexanoyl)silicon tribenzonaphthoporphyrazate.

OBJECTIVE: The aim of the present work is to describe the synthesis and photochemical studies of a silicon tribenzonaphthoporphyrazate (Si-tri-PcNc) derivative to be used in photomedicine. BACKGROUND DATA: Properties of the photosensitizer localization in tumor tissue and photochemical generation of reactive oxygen species are combined with precise delivery of laser-generated light to induce a procedure offering effective local tumoricidal activity. This technique is called photodynamic therapy (PDT). METHODS: This new phthalocyanine (Pc) compound obtained from 2,3-dicyanonaphthalene and phthalonitrile is analyzed and chemically characterized by (1)H-NMR, elemental analyses, infrared (IR), ultraviolet and visibile absorption spectroscopy (UV-Vis) and fluorescence spectra. RESULTS: The spectroscopic analysis of this compound in EtOH showed an electronic spectrum with characteristic bands in the Soret and Q region. Steady-state and time-resolved spectral analyses revealed a fluorescence quantum yield of phi(f) = 0.24, in agreement with other Pc compounds. This compound also shows a triplet excited lifetime of 0.40 microsec in air-saturated solution and a transient with the maximum absorption located at 610 nm, 120 nm shifted to the red if compared to the excited triplet state observed with other Pc compounds. CONCLUSION: Based on our results, we can assume that Si-tri-PcNc induces a higher singlet oxygen production under photoactivation, which is in agreement with the expected photobiological behavior. This result could lead to the testing and eventual use of this new generation of dyes in PDT.

Use of statistical design of experiments to evaluate the sorption capacity of 7-amine-4-azaheptylsilica and 10-amine- 4-azadecylsilica for Cu(II), Pb(II), and Fe(III) adsorption.

7-Amine-4-azaheptylsilica (AAH Si) and 10-amine-4-azadecylsilica (AAD Si) were prepared and used for removal of Cu(II), Pb(II), and Fe(III) from aqueous solutions. Full 2(3) factorial designs with two pseudo-central points were carried out in order to achieve the best conditions of the batch adsorption procedure for metallic ion uptake by the adsorbents. To continue the optimizations, central composite surface design was also employed. These two independent statistical designs of experiments lead to the following conditions: m=30.0 mg of adsorbent; pH 6.0 for Cu(II) and Pb(II), pH 4.0 for Fe(III); t of contact 180 min to guarantee equilibration at higher adsorbate concentration. After optimization of the conditions, isotherms of the metallic ions adsorbed on the AAH Si and AAD Si adsorbents were obtained, which were fitted to nonlinear Langmuir and Freundlich isotherm models.

Hydroxyapatite organofunctionalized with silylating agents to heavy cation removal.

Hydroxyapatite surface silylation with organosilane derivatives (H3CO)3SiR, R being the corresponding organic moieties CH2CH2CH2NH2, CH2CH2CH2NHCH2CH2NH2, and CH2CH2CH2NHCH2CH2NHCH2CH2NH2, was carried out to yield organofunctionalized nanomaterials, named HApR1, HApR2, and HApR3, respectively. The products were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction, thermogravimetry, and (1P and 13C NMR in the solid state. The amounts of groups grafted onto surfaces were 0.75+/-0.05, 2.35+/-0.14, and 2.48+/-0.18 mmolg(-1) for HApRx (x=1,2,3) surfaces, respectively. Linear correlations between elemental analysis, mass loss, (31)P chemical shift data, and the characteristics of the chain of each alkoxysilane were observed. The organic basic centers distributed onto the external surface have the ability to adsorb divalent copper and cobalt cations from aqueous solution. The degree of adsorption obtained from batchwise processes showed the best performance of these synthesized nanomaterials when compared with the pristine hydroxyapatite.