Functionalized Silica Gel Research Articles

Functionalized borazines as precursors for new silica gels

Trialkynylborazines have been prepared in excellent yields by reacting alkynyl-bis(diisopropylamino)borane with powdered ammonium chloride in toluene. These were subsequently used in hydrosilylations with trichlorosilane and trialkoxysilanes using platinum on charcoal as heterogeneous catalyst. This reaction is stereoselective and gives the β-isomers as major product. The tris(β-tricholorsilylvinyl)-substituted derivative (Cl3SiCHCH)3B3N3H3 was isolated in pure form and transformed into a highly functionalized silica gel by a sol–gel process. This gel has a specific surface of about 315 m2 g−1 and is the first containing intact borazine rings. The structures of (iPr2N)2B–CCH, B,B′,B″-(HCCH)3B3N3H3,B,B′,B″-(Me3SiCCH)3B3N3H3 and B,B′,B″-(Cl3Si–CHCH)3B3N3H3 were determined by X-ray structure analyses and are reported.

New Factorial Designs to Evaluate Chemisorption of Divalent Metals on Aminated Silicas

Adsorption processes of Cu(II), Co(II), and Hg(II) on two aminated silica gel surfaces with immobilized ethylenediamine and diethylenediamine groups were studied by a new 23 full factorial design. Two metal quantity levels, temperatures of 25 and 50°C, and silica amounts of 100 and 200 mg were employed. Our study indicates that higher factorial design levels increase adsorption for all metals evaluated, with the exception of the mass parameter. Adsorption is also significantly affected by important antagonistic and synergistic effects involving all factors. Both functionalized silica gel surfaces present higher interactions and good perspectives in preconcentration studies for mercury. The factorial design results are also discussed in terms of some solvation properties for each of the metals studied.

Sensitive and selective ion chromatographic method for the determination of trace beryllium in water samples

A selective and sensitive ion chromatographic method has been developed for the determination of beryllium in a number of water samples at low-μg/l concentrations. The separation was performed on a 250×4.0 mm I.D. iminodiacetic acid functionalised silica gel column. Chromatographed Be(II) was detected using visible detection at 590 nm following post-column reaction with chrome azurol S (CAS). The optimum separation and derivatisation conditions were studied in detail. The optimum eluent conditions were found to be 0.4 M KNO 3, adjusted to pH 2.5 using HNO 3, with optimum post-column detection being achieved using a solution containing 0.26 m M CAS, 2% Triton X-100, 50 m M 2-( N-morpholino)ethanesulfonic acid, pH 6.0. Under the above conditions, the concentration detection limit for Be(II) was found to be 3 μg/l in a standard solution and 4 μg/l in a typical tap water sample, using a 250 μl injection. The method was linear over the investigated range of 10 μg/l to 10 mg/l and highly reproducible. The method was successfully applied to a number of water samples of varying matrix complexity, including simulated seawater, and also to a natural freshwater certified reference material NIST 1640.

Chemisorption of Cu II and Co II chlorides and β-diketonates on silica gel functionalized with 3-aminopropyltrimethoxysilane

Silica gel chemically modified with the silylating agent 3-aminopropyltrimethoxysilane (SAPS) adsorbs Cu II and Co II in the form of chlorides, acetylacetonates and dipivaloylmethanoates from ethanolic solution. The profiles of the chemisorption isotherms present good correlation with the proposed Langmuir model. The amount of adsorbed species in these chemisorption processes showed that only a fraction of the number of active sites was effectively used by β-diketonates, in comparison with the total available number disposed on the matrix. Based on the equilibrium constant the selectivity of the SAPS matrix with β-diketonates, follows the order Co II>Cu II. The chelate of dipivaloylmethanoate with Co II is more pronounced adsorbed on the surface than the correspondent complex of Cu II. This fact reveals the possibility of separating both complexes by using this functionalized silica gel surface. However, for chlorides, this modified surface has preference for both cations.

Cobalt(II) Tetrasulfophthalocyanine Complex Adsorbed on a Silica Gel Surface Chemically Modified with 3-N-Propylpyridinium Chloride: Oxalic Acid Oxidation Study

Cobalt(II) tetrasulfophthalocyanine complex was adsorbed on the 3-N-propylpyridinium chloride functionalized silica gel surface by means of an ion exchange reaction. The specific surface area of the modified silica was SBET= 320 m2 g–1 and the amount of the complex bonded to the substrate surface was 17 mol g–1. A carbon paste electrode made with electrocatalytically oxidized oxalic acid at an anodic potential E=850 mV in 0.5 M KCl solution at pH 2. The anodic peak current intensities were linearly correlated with oxalic acid concentrations between 3.97 and 19.2×10–2 M. The electrode showed a very reproducible response and was chemically very stable under various oxidation-reduction cycles. The electrode was applied in the determination of oxalic acid in a spinach sample.

Iron(II) tetrasulphophthalocyanine complex adsorbed on a silica gel surface chemically modified by 3- n-propylpyridinium chloride

Iron (II) tetrasulphophthalocyanine complex was adsorbed on a 3- n-propylpyridinium chloride functionalized silica gel surface by means an ion exchange reaction. The amount of the complex bonded to the substrate surface, by electrostatic interaction, is 25 μmol g −1 and the specific surface area S BET=320 m 2 g −1. A carbon paste electrode made with the material can electrocatalytically reduce dissolved oxygen to water at a potential Ep c=−140 mV in 0.5 M KCl solution. The plot of the cathodic current against dissolved oxygen concentrations between 0.65 and 14.4 mg dm −3 showed a linear correlation at 298 K and pH 5. The electrode presented a reproducible response and chemically it was stable under various oxidation–reduction cycles.

Tb 3+ molecular photonic devices supported on silica gel and functionalized silica gel

This work reports the luminescence study of Tb 3+ ion and its 1,10-phenantroline (phen), 2,2-bipyridine (bpy) and benzoyltrifluoroacetone (bfa) complexes supported on silica gel (SG) and silica gel functionalized with imidazole propyl (IPG). The emission spectra of these materials showed an increase in the intensity of the Tb 3+ 5D 4 → 7F 5 transition, and it is more intense for the IPG-Tb 3+ system than for SG-Tb 3+ one. The lifetime (τ ms)of the 5D 4 → 7F 5 transition for the IPG-Tb 3+ and SG-Tb 3+ systems was also determined.

Liquid phase oxidations using novel surface functionalised silica supported metal catalysts

Metal species supported on a surface functionalised silica gel are active heterogeneous catalysts for the liquid phase, room temperature epoxidation of cyclohexene and the aerobic oxidation of ethylbenzene.

Immobilization of Crown Ether Carboxylic Acids on Silica Gel and Their Use in Column Concentration of Alkali Metal Cations from Dilute Aqueous Solutions

Eight crown ethers with pendent carboxylic acid groups are immobilized on silica gel and utilized for column concentration of alkali metal cations from dilute aqueous solutions. The column concentration selectivity and efficiency are found to be strongly influenced by (1) the cavity size of the crown ether unit, (2) conformational positioning of the proton-ionizable side arm with respect to the crown ether cavity, and (3) capping of residual silanol surface groups with trimethylsilyl functions. By use of a chromatographic stripping technique, selective column concentration of Na(+), K(+), (Rb(+) and Cs(+)), and Cs(+) by different functionalized silica gels has been achieved.

Liquid chromatographic separation of amino acid enantiomers on a silica-bonded chiral s-triazine column

A chiral derivatizing reagent (CDR) was synthesized by consecutive nucleophilic replacement of two chlorine atoms in 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride) by l-valinamide and l-phenylalaninamide, yielding N-[4-((S)-1- carbamoyl-2- methyl-propylamino)-6- chloro-[1,3,5] triazin-2- yl]- l- phenylalanine . This CDR was used for the derivatization of free dl-amino acids, followed by the liquid chromatographic separation of the diastereomers thus formed, and for the synthesis of a chiral stationary phase (CSP). The CSP was synthesized by substitution of the remaining chlorine atom with aminopropylsilica, yielding {3-[4-(( S)-1-carbamoyl-2-methyl-propylamino)-6-(( S)-1-carbamoyl-2-phenyl-ethylamino)-[1,3,5] triazin-2-ylamino]-propyl}-functionalized silica gel. This new CSP was found to effect, in part very high, resolutions for enantiomers of dansylamino acids when mixtures of acetonitrile and 0.01 M sodium acetate buffer (pH 4) were used as eluents.

Organic complexes of Eu3+ supported in functionalized silica gel: highly luminescent material

Abstract Eu III ion and its chelates of 1,10-phenantroline (phen), 2,2-bipyridine (bpy), benzoyltrifluoroacetone (bfa) and acetylacetone (acac) were supported on silica gel (SG) and silica gel functionalyzed with propyl imidazole (IPG). The luminescence studies of Eu III showed an increase in the intensity and lifetime of the Eu IIII 5 D 0 a 7 F 2 transition in the presense of IPG, when compared with SG. The energy transfer from bfa and phen to the Eu III ion was also detected. In these cases, an increase in the intensity and lifetime of Eu III related to the direct excitation at the metallic ion was observed.

Grafting of Polymers onto Silica Gel Surface ; Polymerization of Vinyl Monomers in the Presence of Functionalized Silica Gel Prepared by Sol-Gel Process

Grafting of Polymers onto Silica Gel Surface ; Polymerization of Vinyl Monomers in the Presence of Functionalized Silica Gel Prepared by Sol-Gel Process

A novel synthetic route for supporting ruthenium complexes on functionalized silica gel

A novel synthetic route for supporting ruthenium complexes on functionalized silica gel

Development of a chemically modified electrode based on carbon paste and functionalized silica gel for preconcentration and voltammetric determination of mercury(II)

A mercury-sensitive chemically modified electrode (CME) based on modified silica gel-containing carbon paste was developed. The functional group attached to the silica gel surface was 3-(2-thiobenzimidazolyl)propyl, which is albe to complex mercury ions. This electrode was applied to the determination of mercury(II) ions in aqueous solution. The mercury was chemically preconcentrated on the CME prior to voltammetric determination by anodic stripping in the differential-pulse mode. A calibration graph covering the concentration range from 0.08 to 2 mg 1 −1 was constructed. The precision for six determination of 0.122 and 0.312 mg 1 −1 Hg(II) was 3.2 and 2.9% (relative standard deviation), respectively. The detection limit for a 5-min preconcentration period was 0.013 mg 1 −1. A study for foreign ions was also made.

ChemInform Abstract: Functionalized Silica Gel as a Support for Solid‐Phase Organic Synthesis.

AbstractDas modifizierte Silicagel (Ia) wird zum Säurechlorid (Ib) umgesetzt, das als Festphasen‐Reagens eingesetzt wird.

Functionalized silica gel as a support for solid-phase organic synthesis

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFunctionalized silica gel as a support for solid-phase organic synthesisJohn F. W. Keana, Masato Shimizu, and Karen K. JernstedtCite this: J. Org. Chem. 1986, 51, 10, 1641–1644Publication Date (Print):May 1, 1986Publication History Published online1 May 2002Published inissue 1 May 1986https://doi.org/10.1021/jo00360a001RIGHTS & PERMISSIONSArticle Views509Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (584 KB) Get e-Alerts Get e-Alerts

Solid-phase synthesis of the self-complementary hexamer d(c7GpCpc7GpCpc7GpC) via the O-3'-phosphoramidite of 7-deaza-2'-deoxyguanosine.

The synthesis of the O-3'-phosphoramidite of a suitably protected 7-deaza-2'-deoxyguanosine (c7G) which is an isostere of 2'-deoxyguanosine is described. The phosphoramidite of the modified nucleoside was used in the synthesis of the self-complementary hexamer d(c7GpCpc7GpCpc7GpC) on functionalized silica gel in a mini-reactor. As expected from the parent hexamer d(GpCpGpCpGpC) the isosteric d(c7GpCpc7GpCpc7GpC) exhibits a rigid secondary structure (22% hypochromicity at 280 nm) and forms a duplex in 1 M aqueous sodium chloride solution. Due to the altered pi-electron system of the pyrrolo[2,3-d]pyrimidine nucleobase, which affects base stacking and hydrogen bonding, the Tm of the modified duplex is decreased by 10 degrees C compared to that of the parent purine hexamer. Moreover, it is expected that the incorporation of c7G influences the pitch of the helix.