Effect of increasing the bidentate chelate ring size in Co(III) complexes on their behavior in salting-out TLC on different adsorbents

The effect of enlargement of the chelate ring size in Co(III) complexes containing bidentate aminocarboxylato and/or diamine ligands on their R-F values in salting-out chromatography has been investigated on thin layers of silica gel, cellulose, polyacrylonitrile, and CN-modified silica gel. Salting-out was achieved with aqueous solutions of ammonium sulfate, Enlargement of the chelate ring caused a decrease in the R-F values of the complexes. By use of linear regression analysis and the theory of error propagation it was established that the logarithms of the separation factors of the pairs of compounds investigated were either unaffected or changed only slightly with changing concentration of salt in the mobile phase; this could not be established for certain on the basis of R-F values alone. Complete correlation was established between the chromatographic behavior of the complexes and the previously investigated effect of successive enlargement of the rings in cobalt(III) complexes containing hexadentate ligands of the EDTA type. The corresponding separation mechanism of the pairs of compounds investigated was also considered. It was finally established that the regularities mentioned were independent of the adsorbent used

Mixed cobalt(III) complexes with S-tyrosine and 1,3-diaminopropane

Four out of six theoretically possible isomers of the (1,3-diaminopropane)bis(S-tyrosinato)cobalt(III) complex, having the cis(O) configuration, were isolated, and the trans(O) isomer was only defined in the eluate. The isomers were separated on an optically active Sephadex QAE column. Geometrical and absolute configurations of the isomers were determined by electronic absorption, circular dichroic and H-1 NMR spectra. The effect of the aromatic side group of the coordinated S-tyrosinato ligand on the stereoselective formation of the obtained isomers was examined

Mixed cobalt(III) complexes with S-tyrosine and 1,3-diaminopropane

Four out of six theoretically possible isomers of the (1,3-diaminopropane)bis(S-tyrosinato)cobalt(III) complex, having the cis(O) configuration, were isolated, and the trans(O) isomer was only defined in the eluate. The isomers were separated on an optically active Sephadex QAE column. Geometrical and absolute configurations of the isomers were determined by electronic absorption, circular dichroic and H-1 NMR spectra. The effect of the aromatic side group of the coordinated S-tyrosinato ligand on the stereoselective formation of the obtained isomers was examined

Synthesis and absolute configuration of novel mono- and dinuclear cobalt(III) complexes containing S-phenylalanine

Two diastereomers of bis(1,3-diaminopropane)(S-phenylalaninato)cobalt(III) were prepared by reaction of S-phenylalanine with carbonatobis(1,3-diaminopropane)cobalt(III). The diastereomers were separated on an optically active Sephadex QAE column and their absolute configurations assigned by means of circular dichroism. In addition, H-1 NMR spectra of the diastereomers were analyzed in terms of the population of the three predominant rotamers of the coordinated S-phenylalaninato ligand. One out of 24 theoretically possible diastereomers of the dinuclear species di-mu-hydroxo-tetrakis(S-phenylalaninato)dicobalt(III) was obtained by direct synthesis and its absolute configuration deduced from CD spectra

Mixed cobalt(III) complexes with aromatic amino acids and diamine. Part IV. Influence of noncovalent intraand interligand interactions on rotamer population of the S-phenylalaninato and S-tyrosinato side groups in (1,2-diaminoethane)bis(S-aminocarboxylato

Rotamer population of S-tyrosinato and S-phenylalaninato ligands side groups in diastereomers of (1,2-diaminoethane)bis(S-aminocarboxylato)cobalt(III) complexes is calculated by vicinal alpha and beta proton coupling constant analysis. The effect of noncovalent intra- and interligand interactions on the population of rotamers in D2O solution is discussed. It has been established that in all the complexes investigated the most abundant is rotamer t, in which aromatic voluminous moiety and carboxylic group are in an anti position. In almost all complexes the lowest content is of rotamer g, in which these two groups are in the nearest position. Relatively high population of rotamer b in complex 5 tyr, in spite of high steric hindrances, is due to intra- and interligand NH... pi interactions

Mixed cobalt(III) complexes with aromatic amino acids and diamine. Part IV. Influence of noncovalent intraand interligand interactions on rotamer population of the S-phenylalaninato and S-tyrosinato side groups in (1,2-diaminoethane)bis(S-aminocarboxylato

Rotamer population of S-tyrosinato and S-phenylalaninato ligands side groups in diastereomers of (1,2-diaminoethane)bis(S-aminocarboxylato)cobalt(III) complexes is calculated by vicinal alpha and beta proton coupling constant analysis. The effect of noncovalent intra- and interligand interactions on the population of rotamers in D2O solution is discussed. It has been established that in all the complexes investigated the most abundant is rotamer t, in which aromatic voluminous moiety and carboxylic group are in an anti position. In almost all complexes the lowest content is of rotamer g, in which these two groups are in the nearest position. Relatively high population of rotamer b in complex 5 tyr, in spite of high steric hindrances, is due to intra- and interligand NH... pi interactions