Thin-layer chromatography on polyacrylonitrile. IV. Investigation of the separation mechanisms for tris-(alkylxanthato)cobalt(III) complexes

The chromatographic behaviour of six tris(alkylxanthato)cobalt(III) complexes on polyacrylonitrile sorbent thin layers was investigated using four non-aqueous and two aqueous solvent systems. It was assumed that their separation under normal-phase conditions was achieved by the mechanism of hydrogen-bond formation between highly electronegative sorbate oxygen and/or sulphur atoms and sorbent methyne group hydrogens. In contrast, it was assumed that under reversed-phase conditions the separation was based on non-specific hydrophobic interactions. Finally, the linear dependence between the number of carbon atoms in the ligands and the corresponding RM values of the investigated complexes of a homologous series was confirmed. © 1992

Thin-layer chromatography on polyacrylonitrile. V. Consideration of separation mechanisms of some aliphatic and aromatic amines

The chromatographic behaviour of ten aliphatic and aromatic amines on thin layers of polyacrylonitrile sorbent was investigated using seven aqueous solvent systems. It was established that an increase in the hydrophobic part of the amines results in their increased retention on this sorbent. A positive linear depencence between the number of carbon atoms in the n-alkyl groups of primary aliphatic amines and the corresponding RM values was also established. The separation of the investigated amines was assumed to be based on non-specific hydrophobic interactions between their non-polar parts and the hydrocarbon chains of the sorbent. © 1992

Investigation of the effect of the aminocarboxylato chelate conformation on the optical activity of the cis(NO2),trans(NH2) -bis(aminocarboxylato)dinitrocobalt/ate(III) isomers

In the cis(NO2),trans(NH2)-bis(aminocarboxylato) dinitrocobalt/ate(III) isomers, containing glycinato, S-alaninato, S-n-valinato, S-valinato, S-n-leucinato, S-leucinato, S-i-leucinato and S-arginine ligands, respectively, it was found that in the Δ-isomers circular dichroic spectra are determined by the configurational contribution to the optical activity. This is connected in the case of optically active ligands with the chair conformation of the chelate rings and the equatorial position of the ring side group. In the Δ-isomers, λ- conformation of the aminocarboxylato chelate rings and the axial position of the ring side groups induce a considerable contribution to the optical activity, which varies from complex to complex. NMR spectroscopy showed that these variations are related to small changes in the chelate ring conformation in such a way that a more axial position of a ring side group induces a larger contribution. The λ-conformation of a S-aminocarboxylato chelate ring induces a large negative contribution to the circular dichroism of the investigated complexes. © 1988

A kinetic investigation of the tris(4-morpholinecarbodithionato-S,S') cobalt(III) complex formation by the intralattice and interlattice reactions

The kinetics of tris-(4-morpholinecarbodithionato-S,S) cobalt(III) formation by the intralattice and interlattice reactions of hexaaminecobalt(III) cation with dithiocarbamato anion was investigated under isothermal conditions. The intralattice reaction, conducted in the solid hexaaminecobalt(III) 4-morpholinecarbodithionate salt, proceeded well at temperatures of 50-80°C, conforming to the phase boundary Rn reaction mechanism (Ea = 92.6 kJ mol-1, A = 5.28 × 109 s-1). The interlattice reaction, conducted in the mixture of hexaaminecobalt(III) chloride and potassium 4-morpholinecarbodithionate powders, proceeded well at temperatures of 140-200° C. The effect of the particle size of the powders and of the powder packing pressure on the kinetic parameters were also investigated. In the first half of the reaction, the random nucleation F1 mechanism seems to operate (Ea = 200-265 kJ mol-1, A = 8.6 × 1018-3.6 × 1027s-1); later the diffusional mechanism prevails. In addition, a fast initial process in the interlattice reaction has been discovered and investigated at lower temperatures (80-115° C). It conforms to the random nucleation F1 reaction mechanism (Ea = 63 kJ mol-1, A = 1.6 × 105 s-1). © 1993

Effect of electronegativity of donor atoms on RF values of tris(β-diketonato) complexes of cobalt(III), chromium(III) and ruthenium(III) by thin-layer chromatography on silica gel

The effect of the electronegativity of donor atoms on RF values obtained by TLC on silica gel was investigated with two series of complexes of the type [M(acac)3-n(phacphac)n] and [M(acac)3-n(phacphSac)n], where M is Co(III), Cr(III) or Ru(III), acac=2,4-pentandionato ion, phacphac=1,3-diphenyl-1,3-propanedionato ion and phacphSac=3-mercapto-1,3-diphenyl-prop-2-en-1-on ion (n=0-3). Development was with nine single and six two-component solvent systems. The RF values of the complexes increase by replacing one oxygen atom of a β-diketonato ligand with a less electronegative sulphur atom. A positive linear dependence between the RM values of the complexes and the numbers of acac substituted by phacphSac ligands was established. The separation mechanisms and separation factors are discussed. © 1993 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH