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  • Author or Editor: Rada Baošić x
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The effect on chromatographic behavior, on thin layers of silica gel, of the electronegativity of ligator atoms has been studied for three series of β-diketonato complexes of the type [M(acac) 3− n (phacphac) n ], [M(acac) 3− n (phacphSac) n ], and [M(acac) 3− n (phSacphSac) n ] (where M represents cobalt(III), chromium(III) or ruthenium(III), acac is the 2,4-pentanedionato ion, phacphac is the 1,3-diphenyl-1,3-propanedionato ion, phacphSac is 3-mercapto-1,3-diphenyl-prop-2-en-1-one, phSacphSac is the 3-mercapto-1,3-diphenyl-prop-2-en-1-tion ion, and n = 0–3). For chromatographic separations, ten typical normal-phase mobile phases were used, five mono-component and five two-component. For all the complexes examined it was found that substitution of the donor oxygen atom by a less electronegative sulfur atom resulted in increased mobility of the complex. It was also established that substitution of the acac ligand resulted in increased hR F values. For all the complexes examined a linear dependence was observed between the R M values of the complexes and the number of acac ligands substituted by phSacphSac ligands. On the basis of these results, possible separation mechanisms are discussed.

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The effect of substituents of the β -ketoiminato ligand of 24 copper(II) and nickel(II) complexes on hR F values obtained by TLC on polyacrylonitrile (PAN) has been studied. Chelate ligands were prepared by condensation of diamine (dm) and the corresponding β -diketone. Copper(II) and nickel(II) complexes with chelate ligands containing ethylenediamine (en = 1,2-diaminoethane) or propylene diamine (pn = 1,2-diaminopropane) as the amine part and acetylacetone (acac = 2,4-pentanedionato ion) and/or phenylacetylacetone (phacac = 1-phenyl-1,3-pentanedionato ion), and/or trifluoroacetylacetone (tfacac = 1,1,1-trifluoro-1,3-pentanedionato ion), i.e. phenylacetylacetone as β -diketone, were synthesized. Ten non-aqueous mobile phases (six mono-component and four two-component) and two aqueous mobile phases were used for chromatographic separation. The results revealed that the mobility of the complexes decreased on substitution of the CH 3 group in the β -ketoiminato ligand by CF 3 or C 6 H 5 . The chromatographic behavior of the complexes on PAN was compared with that on other adsorbents. Possible separation mechanisms are discussed.

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The effect of the central ion of tris- β -diketonato complexes of transition metals on their hR F values in thin layer chromatography (TLC) on silica gel has been investigated for 24 Co(III), Cr(III), and Ru(III) complexes of the types [M(acac) 3− n (phacphac) n ] and [M(acac) 3− n (phacphSac) n ], where n = 0–3, and with four complexes of the type [M(acac) 3 ], where M = Sc(III), Y(III), Nd(III), or La(III), acac is the 2,4-pentanedionato ion, phacphac is the 1,3-diphenyl-1,3-propanedionato ion, and phacphSac is the 3-mercapto-1,3-diphenylprop-2-en-1-one ion. One- and two-component non-aqueous mobile phases were used for the chromatographic separations. The dependence of retention data on the length of ionic radius and on En/r i value is discussed. The mobility ( hR F values) of the tris(acetylacetonato) complexes on thin layers of silica gel is directly proportional to the ionic radius of the central ion. On the basis of the results obtained, adsorption was assumed to be the dominant mechanism of separation under the chromatographic conditions used.

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Experimental R M values for two series of β-diketonato complexes, M(acac) 3- n (phacphac) n and M(acac) 3- n (phSacphSac) n , where M represents cobalt(III) or chromium(III), have been determined by reversed-phase thin-layer chromatography on RP-18 silica with binary tetrahydrofuran-water, acetonitrile-water, and acetone-water mobile phases. R M 0 values were determined for the different mobile phase mixtures by linear extrapolation to 0% ( v/v ) organic modifier. Lipophilicity C 0 was calculated as the ratio of the intercept and slope values. Chromatographically obtained lipophilicity was correlated with calculated C log P values.

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