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Biomedical subjects

Robin D Rogers

Publications and source records attributed to Robin D Rogers.

At least 37 records · Page 2Linked to original sources
PubMed2004

Nickel(II), copper(II) and zinc(II) binding properties and cytotoxicity of tripodal, hexadentate tris(ethylenediamine)--analogue chelators.

Three tripodal hexamine chelators based on cis,cis-1,3,5-triaminocyclohexane (tach) have been synthesized and their aqueous coordination chemistry with Ni(II), Cu(II) and Zn(II) is reported. The chelators have a 2-aminoethyl pendant arm attached to each nitrogen of tach, specifically 'tachen'(N,N',N''-tris(2-aminoethyl)cyclohexane-cis,cis-1,3,5-triamine), and two with S,S,S-chiral pendant arms, 'tachpn'(N,N',N''-tris(2-aminopropyl)cyclohexane-cis,cis-1,3,5-triamine) and 'tachbn'(N,N',N''-tris(2-amino-3-phenylpropyl)cyclohexane-cis,cis-1,3,5-triamine. These chelators complex Ni(II), Cu(II) and Zn(II) in aqueous or aqueous/methanolic medium. The crystalline products [M(II)L](X)2 are isolated, where M = Ni(II), Cu(II) or Zn(II), L = tachen, tachpn or tachbn, and X = ClO4-. Crystallographic study of selected tachpn and tachbn complexes shows the chelate arms are constrained in a Lambda(deltadeltadelta) configuration about M(II), which is attributed to their chirality. Solution UV-vis spectroscopy of the Ni(II) and Cu(II) complexes indicates six-coordination and little effect of the pendant arm substitution on ligand-field strength. The single exception is [Cu(tachbn)]2+, whose spectrum is consistent with five-coordination in solution. The cytotoxicities of tachen, tachpn and tachbn toward cultured cancer cells is in the order tachen < tachpn < tachbn < tachpyr, where tachpyr is the aminopyridyl chelator N,N',N''-tris(2-pyridylmethyl)cyclohexane-cis,cis-1,3,5-triamine. The cytotoxicity difference is attributed to an order of increasing lipophilicity, tachen < tachpn < tachbn.

Animals↗
PubMed2004

Experimental and computational studies of the metal-metal stretching vibration in X(3)MMX(3) compounds (X = alkoxide, alkyl, amide).

Raman spectra of a number of triply bonded M(2)X(6) (M = Mo, W; X = alkoxide, alkyl) compounds have been obtained. Several exhibit a band assignable to the metal-metal stretching vibration nu(M)(M). This band was not identified in earlier studies of the M(2)(NMe(2))(6) compounds. We have attempted to correlate the Raman vibrational data with structural data from single-crystal X-ray diffraction studies. Diffraction studies of the M(2)(O-1-4-pentyl[2.2.2]bicyclooctyl)(6) species show a crowded environment around the dimetal core, but the M-M-O angles differ substantially from 90 degrees. Thus, this angle does not solely determine the extent to which the metal-metal and ligand-based vibrational modes couple and, in turn, our ability to observe nu(M)(M). Computational studies of model systems confirm the assignment of the band as being nu(M)(M), although the predicted vibrational energies are consistently too high by ca. 7%. The computational results suggest that a nu(M)(M) band may be present in the published spectra of the M(2)(NMe(2))(6) pair.

Journal Article↗
PubMed2004

Using Caenorhabditis elegans to probe toxicity of 1-alkyl-3-methylimidazolium chloride based ionic liquids.

Ionic liquids are gaining attention as new solvents within the green chemistry community; however this attention has quickly outstripped current environmental and toxicological data available. In the present communication, we establish the use of Caenorhabditis elegans as a model organism for inexpensively and quickly exploring toxicological effects of 1-alkyl-3-methylimidazolium chloride ionic liquids.

Animals↗
PubMed2003

Synthesis of benzo[c]selenophene and derivatives via new routes.

[reaction: see text] Benzo[c]selenophene has been generated via facile bromination-dehydrobromination as well as oxidation of the 1,3-dihydrobenzo[c]selenophene. Benzo[c]selenophene thus generated has been lithiated in situ and treated with ClCOOEt to give the first functionalized derivative subject to X-ray crystallographic analysis.

Journal Article↗
PubMed2003

Uranyl coordination environment in hydrophobic ionic liquids: an in situ investigation.

Different inner-sphere coordination environments are observed for the uranyl nitrate complexes formed with octyl-phenyl-N,N-diisobutylcarbamoylmethylphosphine oxide and tributyl phosphate in dodecane and in the hydrophobic ionic liquids (ILs) [C(4)mim][PF(6)] and [C(8)mim][N(SO(2)CF(3))(2)]. Qualitative differences in the coordination environment of the extracted uranyl species are implied by changes in peak intensity patterns and locations for uranyl UV-visible spectral bands when the solvent is changed. EXAFS data for uranyl complexes in dodecane solutions is consistent with hexagonal bipyramidal coordination and the existence of UO(2)(NO(3))(2)(CMPO)(2). In contrast, the complexes formed when uranyl is transferred from aqueous nitric acid solutions into the ILs exhibit an average equatorial coordination number of approximately 4.5. Liquid/liquid extraction results for uranyl in both ILs indicate a net stoichiometry of UO(2)(NO(3))(CMPO)(+). The concentration of the IL cation in the aqueous phase increases in proportion to the amount of UO(2)(NO(3))(CMPO)(+) in the IL phase, supporting a predominantly cation exchange mechanism for partitioning in the IL systems.

Journal Article↗
PubMed2003

Liquid clathrate formation in ionic liquid-aromatic mixtures.

1-Alkyl-3-methylimidazolium containing ionic liquids with hexafluorophosphate, bis(trifyl)imide, tetrafluoroborate, and chloride anions form liquid clathrates when mixed with aromatic hydrocarbons; in the system 1,3-dimethylimidazolium hexafluorophosphate-benzene, the aromatic solute could be trapped in the solid state forming a crystalline 2:1 inclusion compound.

Journal Article↗
PubMed2003

1,3-dimethylimidazolium-2-carboxylate: the unexpected synthesis of an ionic liquid precursor and carbene-CO2 adduct.

1,3-Dimethylimidazolium-2-carboxylate is formed in good yield, rather than the anticipated organic salt, 1,3-dimethylimidazolium methyl carbonate, as the reaction product resulting from both N-alkylation and C-carboxylation of 1-methylimidazole with dimethyl carbonate; the crystal structure of the zwitterion exhibits pi-stacked rings and two-dimensional sheets constructed by hydrogen-bonds from imidazolium-ring hydrogens to the carboxylate group.

Journal Article↗
PubMed2002

Application of ionic liquids as plasticizers for poly(methyl methacrylate).

The room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, [C4mim][PF6] was found to be an efficient plasticizer for poly(methyl methacrylate), prepared by in situ radical polymerization in the ionic liquid medium; the polymers have physical characteristics comparable with those containing traditional plasticizers and retain greater thermal stability.

Free Radicals↗
PubMed2002

Conventional free radical polymerization in room temperature ionic liquids: a green approach to commodity polymers with practical advantages.

Free-radical polymerization of methyl methacrylate and styrene using conventional organic initiators in the room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) is rapid and produces polymers with molecular weights up to 10x higher than from benzene; both polymerization and isolation of products were achieved without using VOCs, offering economic as well as environmental advantages.

Benzoyl Peroxide↗
PubMed2002

Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg2+ and Cd2+: synthesis, characterization, and extraction studies.

A series of hydrophobic task-specific ionic liquids designed to extract Hg2+ and Cd2+ from water were prepared by appending urea-, thiourea-, and thioether-substituted alkyl groups to imidazoles and combining the resulting cationic species with PF6-. The new ionic liquids were characterized and investigated for their metal ion extraction capabilities. When used in liquid/liquid extraction of Hg2+ and Cd2+ from aqueous solutions, the metal ion distribution ratios increased several orders of magnitude, regardless of whether the ionic liquids were used as the sole extracting phase or doped into a series of [1-alkyl-3-methylimidazolium][PF6] (alkyl = n-C4-C8) ionic liquids to form a 1:1 solution. In the 1:1 mixtures, as the length of the alkyl chain increased from butyl to hexyl to octyl, the metal ion distribution ratios increased. Increasing the ratio TSIL/[C4mim][PF6] resulted in higher distribution ratios for both Hg2+ and Cd2+. Overall, the thiourea- and urea-derivatized cations yielded the highest distribution ratios, and those for Hg2+ were higher than those for Cd2+; however, a change in aqueous-phase pH does not promote the stripping of metal ions from the extracting phase. The combination of these imidazolium cations and PF6- produced ionic liquids with decreased thermal stability in comparison to [C(n)mim]-[PF6]. Gaussian98 restricted Hartree-Fock geometry optimizations for one of the thiourea-appended cations shows the charge delocalization around the ring and suggests that the thiourea group may aid in deprotonating the imidazolium ring and may be responsible for the lowered thermal stability of these cations.

Cadmium↗
PubMed2002

Dissolution of cellulose [correction of cellose] with ionic liquids.

We report here initial results that demonstrate that cellulose can be dissolved without activation or pretreatment in, and regenerated from, 1-butyl-3-methylimidazolium chloride and other hydrophilic ionic liquids. This may enable the application of ionic liquids as alternatives to environmentally undesirable solvents currently used for dissolution of this important bioresource.

Cellulose↗
PubMed2002

Condensed thiophenes and selenophenes: thionyl chloride and selenium oxychloride as sulfur and selenium transfer reagents.

3,4-Cyanomethyl substituted thiophenes reacted with thionyl chloride in the presence of base to give dicyano substituted thieno(3,4-c)thiophenes. The use of selenium oxychloride furnished the corresponding cyano substituted seleno(3,4-c)thiophene. 1,2-Phenylenediacetonitriles gave the corresponding cyano substituted benzo(c)thiophenes and benzo(c)selenenophenes, respectively, upon reaction with thionyl chloride and selenium oxychloride in the presence of base.

Journal Article↗
PubMedDate not supplied

Production of bioactive cellulose films reconstituted from ionic liquids.

A new method for introducing enzymes into cellulosic matrixes which can be formed into membranes, films, or beads has been developed using a cellulose-in-ionic-liquid dissolution and regeneration process. Initial results on the formation of thin cellulose films incorporating dispersed laccase indicate that active enzyme-encapsulated films can be prepared using this methodology and that precoating the enzyme with a second, hydrophobic ionic liquid prior to dispersion in the cellulose/ionic liquid solution can provide an increase in enzyme activity relative to that of untreated films, presumably by providing a stabilizing microenvironment for the enzyme.

Catalysis↗
PubMedDate not supplied

Ionic liquid-reconstituted cellulose composites as solid support matrices for biocatalyst immobilization.

Preparation of cellulose-polyamine composite films and beads, which provide high loading of primary amines on the surface allowing direct one-step bioconjugation of active species, is reported using an ionic liquid (IL) dissolution and regeneration process. Films and bead architectures were prepared and used as immobilization supports for laccase as a model system demonstrating the applicability of this approach. Performance of these materials, compared to commercially available products, has been assessed using millimeter-sized beads of the composites and the lipase-catalyzed transesterification of ethyl butyrate.

Biocompatible Materials↗
PubMedDate not supplied

Correlation of the melting points of potential ionic liquids (imidazolium bromides and benzimidazolium bromides) using the CODESSA program.

The melting points of several imidazolium-based ionic liquids or ionic liquid analogues were correlated using the CODESSA program in order to develop predictive tools for determination of suitable ionic liquid salts. The data set consisted of melting point data (degrees C) for 104 substituted imidazolium bromides divided on the basis of the N-substituents into three subsets: A-57 compounds, B-29 compounds, and C-18 compounds. The 45 benzimidazolium bromides form set D. Five-parameter correlations were obtained for (i) set A with R2 = 0.7442, (ii) set B with R2 = 0.7517, and (iii) set D with R2 = 0.6899, while set C was correlated with a three parameter equation with R(2) = 0.9432. These descriptors for predicting the melting points of the imidazolium and benzimidazolium bromides were based on the size and electrostatic interactions in the cations.

Journal Article↗