Browsing by Author "Bartsch, Richard A. (TTU)"
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Item Effect of Na+ on solvent extraction of alkaline earth metal cations by proton-ionizable calix[4]arenes(2010) Talanova, Galina G.; Talanov, Vladimir S.; Surowiec, Kazimierz (TTU); Bartsch, Richard A. (TTU)Metal ion recognition by proton-ionizable calixarenes is often affected by interference from the Na+ present in many aqueous solutions. To assess the Na+ -effect on calixarene selectivity towards alkaline earth metal cations (AEMC), competitive solvent extraction of Mg2+, Ca2+, Sr2+ , and Ba2+ from aqueous solutions into chloroform by di-ionizable calix[4]arene N- (trifluoromethylsulfonyl)carboxamides and corresponding carboxylic acids, conformationally mobile and restricted to cone, partial cone and 1,3-alternate conformations, was investigated in the absence and in the presence of aqueous-phase Na+ . The extraction selectivities were found to be altered due to contrasting Na+ -induced changes in the AEMC uptake. Observed increases in loadings of smaller AEMC are rationalized by their co-extraction with Na+.Item Metal ion complexation in acetonitrile by upper-rim benzyl-substituted, di-ionized calix[4]arenes bearing two dansyl fluorophores(2010) Ocak, Űmmühan; Ocak, Miraç; Shen, Xin (TTU); Gorman, Alexander H. (TTU); Surowiec, Kazimierz (TTU); Bartsch, Richard A. (TTU)The influence of Li+ , Na+ , K+ , Rb+ , Cs+ , Mg2+, Ca2+, Sr2+, Ba2+, Ag+ , Cd2+, Co2+, Fe2+, Hg2+ , Mn2+, Pb2+, Zn2+ and Fe3+ on the spectroscopic properties of two dansyl (1- dimethylaminonaphthalene-5-sulfonyl) groups linked to the lower rims of a series of three, structurally related, di-ionized calix[4]arenes is investigated by means of emission spectrophotometry. Di(tetramethylammonium) salts of the di-ionized ligands, L, L1 and L2, which differ in having no, two and four benzyl groups, respectively, on the upper rim of the calix[4]arene scaffold, are utilized for the spectrofluorimetric titration experiments in MeCN. On complexation by alkaline earth metal cations, the emission spectra undergo marked red shifts. Alkali metal cations cause fluorescence enhancement of benzyl-substituted di-ionized calix[4]arenes L1 and L2 with red shifts, except for Li+ and Cs+ . Transition metal cations and Pb2+ interact strongly with the ligands. In particular, Fe3+ , Hg2+ and Pb2+ cause greater than 99 % quenching of the dansyl fluorescence for all three ligands.Item Polybenzocrown ethers: synthesis by cesium-assisted cyclization and solid-state structures(2010) Hanes, Robert E. Jr.; Ellingsworth, Edward C.; Griffin, Scott T.; Rogers, Robin D.; Bartsch, Richard A. (TTU)A series of large-ring polybenzocrown ethers is prepared by cesium-assisted cyclizations. Reactions of diphenols/bisphenols, dimesylates of oligoethylene glycols and cesium carbonate in MeCN produce the large-ring polybenzocrown ethers in high yields. To gain further insight into the structures of these compounds, solid-state structures of three large-ring crown ethers are obtained by X-ray diffraction.Item Preparation of benzo- and polybenzocrown ethers by macrocyclization reactions(2010) Hanes, Robert E. Jr.; Lee, Jong Chan (TTU); Ivy, Sheryl N. (TTU); Palka, Anna (TTU); Bartsch, Richard A. (TTU)Macrocyclization of crown ethers and their methods of preparation were explored. We present a robust, scalable method for the preparation of these macrocycles. Additionally, the effect of changing the structures of the precursors was explored to determine whether the ‘cut’ of bisphenol and dimesylate influenced the course of the reaction as measured by the yield. Further, using catechol derivatives, the method was used for the preparation of monobenzocrown ethers. Interestingly, for the preparation of monobenzocrown ethers, [2+2] adducts were discovered to be significantly contaminating the products. Dimesylates were chosen as the leaving group due to their ease or preparation and the ability to use the unpurified products with no apparent impact on the macrocyclization.Item Sterically congested, geminal aryl-substituted, proton-ionizable sym-dibenzo-16-crown-5 lariat ethers: synthesis and alkali metal cation extraction(2010) Tu, Chuqiao (TTU); Jang, Youngchan (TTU); Bates, Carrie L. (TTU); Gega, Jerzy (TTU); Surowiec, Kazimierz (TTU); Bartsch, Richard A. (TTU)Three series of proton-ionizable sym-dibenzo-16-crown-5 ethers with sterically demanding 1- naphthyl, 2-naphthyl, and 9-phenanthryl geminal groups are synthesized and characterized. Variation of the proton-ionizable group includes oxyacetic acid and N-(X)sulfonyl oxyacetamide units with X = Me, Ph, C6H4-4-NO2, and CF3. For the latter series, variation of X provides 'tunable' acidity of the ligand. The metal ion-complexing properties of the proton-ionizable sym- (aryl)dibenzo-16-crown-5 compounds are probed by competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform.Item Synthesis, structure and metal ion binding of di-(1,8-naphtho)-16-crown-4 compounds(2010) Torun, Lokman (TTU); Mueller, Peter; Cao, Xiaodan (TTU); Bartsch, Richard A. (TTU)The syntheses of two di(1,8-naphtho)-16-crown-4 compounds are described. In the X-ray structure of di(1,8-naphtho)-16-crown-4, the compound crystallizes in the orthorhombic space group Pna21 with four molecules per asymmetric unit. Alkali metal cation selectivities of the ionophores are assessed in solvent polymeric membrane electrodes.Item Tri-ionizable calix[4]arene ligands: synthesis and lanthanide ion complexation(2010) Fernandez, Fernando A.; Bartsch, Richard A. (TTU); Arnaud-Neu, Françoise; Hubscher-Bruder, Véronique; Michel, SylvieNew proton-ionizable p-tert-butylcalix-4-arene ligands with three N-(X)sulfonyl oxyacetamide groups and one methoxy group on the lower rim capable of forming electroneutral complexes with trivalent lanthanide ions are synthesized. Variation of the electron-withdrawing ability of X (Me, Ph, C6H4-4-NO2, CF3) is used to tune the ligand acidity. Conformations of the ligands in CDCl3 are investigated by variable temperature NMR spectroscopy. By potentiometric titration, complexation of La3+, Eu3+, and Yb3+ by the tri-ionizable complexing agents in MeOH is probed.