Thin-layer chromatography of binary mixtures of metal complexes including isomers

Summary Complexes of 2,6 pyridine-bis-glyoxal-o-mercaptylanil and thiophene-2-glyoxal-o-pyridineanil with Fe(III), Co(II), Ni(II) and Cu(II), isolated as binary mixtures, were quantitatively resolved on thin layers of silica gel and their compositions were determined. Separation of mixtures in bulk was by column chromatography. Resolved components, including cis- trans and structural isomers, were identified by correlating their R_F values with spectral properties.     

Diantipyrilmethane as complex-forming reagents in the thin-layer chromatographic determination of metals

Summary The efficiency of diantipyrilmethane used as a reagent for the chromatographic separation of metals, including titanium, zirconium and hafnium, rare earth elements, transition and platinum metals is shown. The peculiarities of the chromatographic behaviour of metal diantipyrilmethanates and the mechanism of their retention in TLC are discussed. Methods were developed for the determination of metals based on complex formation directly in the sorbent layer or by liquid extraction. The chromatographic separation takes place in silica gel thin layers with elution by organic solvent-mineral acid mixtures. The metals are determined by densitometric or spectrophotometric methods. After the complexes are isolated from the layer. The procedures are characterized by simplicity, efficiency, and a rather high selectivity. They were used to analyze steels, alloys, industrial solutions and other samples.     

Thin-layer chromatography of isomeric pairs of chalkones and flavanones

Summary A fundamental two-dimensional thin-layer chromatographic technique using silica gel as adsorbent for the detection and identification of isomeric pairs of chalkones and flovanones is described. The proposed method is simple, inexpensive and needs no sophisticated instruments.     

Thin-layer chromatographic separation of some closely related olefinic benzo- and naphtofurans

Summary A method is reported for the separation of 16 closely related 2-(1, 2-diphenylvinyl)-3-phenylbenzofuran and 2-(1, 2-diphenylvinyl)-1-phenylnaphtho[2,1-b] furan derivatives on thin-layers of silica gel-G.     

Thin-layer chromatography of metal ions on bonded stationary phases

Summary The separation of iron, copper, nickel, and zinc by thin-layer chromatography was studied. Eight bonded-phase silica substrates and twenty-nine solvent systems were investigated. Solutions of 1% diphenylcarbazide in ethanol and 1% K₄Fe(CN)₆ in water were used to detect the metal ions. The best separation was obtained with an immobilized trifluoroacetylacetone substrate and 10% trifluoroacetylacetone in acetone mobile phase.     

Thin-layer chromatography of low-molecular epoxy compounds after derivatization with picric acid

Summary Optimum conditions were obtained for the determination of low-molecular epoxides by a method based on derivatization with picric acid and thin-layer chromatography on silica gel. The chromatograms were visualized with solutions of primary, secondary or tertiary amines in acetone. Most of the monoepoxides gave only one spot; diepoxides gave two spots. The detection limits for highly reactive epoxy compounds (derivatization time less than 2 hours) were estimated to be approx. 0.02 μmole.     

The steric effect of o-tolyl ligand on the fluxionality behavior of some binuclear organoplatinum(II) complexes with bis(diphenylphosphino)methane as bridging ligand

A series of binuclear organoplatinum(II) complexes of general formula cis,cis-[R₂Pt(μ-SMe₂)(μ-dppm)Pt(o-MeC₆H₄)₂], 3a-3d, in which R = Ph, p-MeC₆H₄, m-MeC₆H₄ or p-MeOC₆H₄, were prepared by the reaction of monomeric precursors [Pt(o-MeC₆H₄)₂(dppm)] and cis-[PtR₂(SMe₂)₂]. The binuclear dialkyl analogs, in which R = Me (3e) or R₂ = {(CH₂)₄} (3f), were prepared by the reaction of cis-[Pt(o-MeC₆H₄)₂ (SMe₂)₂] and [PtR₂ (dppm)]. The complexes were fully characterized by multinuclear (¹H, ¹³C, ³¹P, ¹⁹⁵Pt) NMR spectroscopy each as a mixture of syn and anti isomers (depending on the relative orientations of Me substituents on o-tolyl ligands) and each isomer was shown to have a rigid structure. Other binuclear analogs , 3g-3j, in which R is a less steric demanding aryl groups m-MeC₆H₄ or p-MeOC₆H₄, and R′ = Me or , were prepared by the reaction of cis-[PtR₂(SMe₂)₂] and , and shown to have fluxional structures.     

Salting-out thin-layer chromatography of transition metal complexes. IV: Effect of sorbent on the behaviour of mixed aminocarboxylato cobalt (III) complexes

Summary From literature data for 14 mixed aminocarboxylato cobalt(III) complexes, the effect of the sorbent on R_M values, salting-out efficiency (m) and separation factors () of adjacent members of homologous series was investigated in salting-out, thin-layer chromatography on silica gel, polyacrylonitrile and cellulose sorbents, using ammonium sulphate solutions as developers. For complexes belonging to the same homologous series, linear dependence was found between R_M,m and log values, respectively, on two different sorbents. Polyacrylonitrile was shown to be the most suitable sorbent for the separation of the complexes since it gave the highest values for R_M,m and .     

Thin-layer chromatography of benzamides on cellulose and unconventional starch and aminoplast supports

Summary The retention behaviour and separation ability of cellulose, starch and aminoplast thin-layers with aqueous and non-aqueous mobile phases has been studied by measuring the retention of a homologous series of benzamides. The retention behaviour and separation ability are discussed in terms of the nature of the solute, support and eluent.     

Molecular mechanics modelling of Pt(II) complexes with antitumor activity. Influence of the type and the positions of the ring substituents on the conformational energies and thermodynamic stabilities

Summary The influence of the type and the positions of the ring substituents on the conformational energies and thermodynamic stabilities of a series of Pt(II) complexes of the general formula [1,2-bis(hydroxyphenyl)ethylenediamine]PtL ₂(L ₂=2Cl^–, 2I^–, SO ₄ ^2– ) has been studied by molecular mechanics. The calculations were carried out for the ligand conformations (R,S/S,R)-, (R,S/S,R)-, (R,R)-, and (S,S)-. The obtained energies and thermodynamic stabilities are in agreement with experimental data on the reactivity and antitumor activity of the compounds.

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Molecular Modelling von Pt(II)-Komplexen mit Antitumoraktivität. Einfluß von Art und Position von Substituenten auf Konformationsenergien und thermodynamische Stabilitäten

Zusammenfassung Die konformationellen Energien und thermodynamischen Stabilitäten einer Reihe von Pt(II)-Komplexen mit der allgemeinen Formel [1,2-bis(Hydroxyphenyl) ethylendiamin]PtL ₂(L ₂=2Cl^–, 2I^–, SO ₄ ^2– ) wurden mittels molekularmechanischer Methoden in Abhängigkeit von Art und Stellung der Substituenten an den Phenylringen untersucht. Die Berechnungen wurden für die Ligandenkonformationen (R,S/S,R)-, (R,S/S,R)-, (R,R)- und (S,S)- durchgeführt. Die erhaltenen Energien und Stabilitäten stimmen mit experimentellen Daten über Reaktivität und Antitumoraktivität der Verbindungen überein.

     

Thin-layer chromatography of metal ions on a new carbamide-formaldehyde polymer

Summary A number of metal ions were systematically chromatographed on thin-layer of a newly synthesized carbamide-formaldehyde polymer using neutral and acidic eluents. For comparison, metal ions were also chromatographed on cellulose layers with the same eluents.     

Thermoanalytical and gas chromatographic properties of the copper(II) complexes of alkyl-substituted Schiff's bases

Summary A study is presented of the thermoanalytical and gas chromatographic (GC) properties of the copper(II) complexes of twenty four tetradenate Schiff's bases. Variations in thermal stability, volatility and GC retention of the complexes are discussed in terms of stereo-electronic effects of the substituents. Although some complexes decomposed extensively during vaporization above 250°C all, apparently, survive chromatography intact at 200°C. Certain complexes were separated as distinct regio-isomers by GC. Fluorinated ligands still appear to be the most suitable derivatizing reagents for Cu(II).     

Heteroleptic platinum(II) and palladium(II) complexes with thiacrown and diimine ligands

We wish to report the synthesis, crystal structures, spectroscopic and electrochemical properties of several new Pt(II) heteroleptic complexes containing the thiacrown, 9S3 (1,4,7-trithiacyclononane) with a series of substituted phenanthroline ligands and related diimine systems. These five ligands are 5,6-dimethyl-1,10-phenanthroline(5,6-Me₂-phen), 4,7-dimethyl-1,10-phenanthroline(4,7-Me₂-phen), 4,7-diphenyl-1,10-phenanthroline(4,7-Ph₂-phen), 2,2′-bipyrimidine(bpm), and pyrazino[2,3-f]quinoxaline or 1,4,5,8-tetraazaphenanthrene(tap). All complexes have the general formula [Pt(9S3)(N₂)](PF₆)₂ (N₂ = diimine ligand) and form similar structures in which the Pt(II) center is surrounded by a cis arrangement of the two N donors from the diimine chelate and two sulfur atoms from the 9S3 ligand. The third 9S3 sulfur in each structure forms a longer interaction with the platinum resulting in an elongated square pyramidal structure, and this distance is sensitive to the identity of the diimine ligand. In addition, we report the synthesis, structural, electrochemical, and spectroscopic properties of related Pd(II) 9S3 complex with tap. The ¹⁹⁵Pt NMR chemical shifts for the six Pt(II) complexes show a value near −3290 ppm, consistent with a cis-PtS₂N₂ coordination sphere although more electron-withdrawing ligands such as tap show resonances shifted by almost 100 ppm downfield. The physicochemical properties of the complexes generally follow the electron-donating or withdrawing properties of the phenanthroline substituents.     

Salting-out thin layer chromatography of transition metal complexes: A comparative study of the effect of increased number of CH2 groups in chelate rings

Summary The regularities previously established in salting-out thin-layer chromatography on silica gel of Co(III) complexes, in which the side chains of a specific chelate ring were successively increased in length, were also found to be valid for two series of Co(III) complexes of the EDTA type, in which different chelate rings were enlarged by one CH₂ group. It was found that in the case of complexes of the EDTA type the salting-out efficiencies were practically the same for all members of a series, while the values of the separation factors were paractically independent of the ammonium sulphate concentration in the solvent system used. The results obtained were consistent with the mechanism of nonspecific hydrophobic interactions. The method used can be applied to the separation of the members of the series of complexes that we investigated.     

Thin-layer chromatography with high-boiling mobile phase. part 2: Effect of temperature on retention characteristics in TLC with high-boiling mobile phases

A study has been undertaken on the effect of temperature on retention characteristics in thin-layer chromatography (TLC) with low-volatility mobile phases (MP). It is shown that temperature variations in TLC in melts bring about variations in both the relative retention values and, in some cases, in the order of migration of the chromatographic zones across the layer. The variation in the capacity factor k' with temperature agrees well with Martin's equation. To explain the temperature dependence of R_f one must, in general, take into account the variations with temperature in both the partition coefficient and the phase ratio. To describe the variation in R_f with temperature in TLC with low-volatile MP one can use an approximate equation in which In R_f is a linear function of 1/T. The experiments indicate that temperature is a major factor in TLC in melts.     

Thin-layer chromatographic separation and identification of some anions on copper sulphate impregnated silica gel layers

Summary Thin-layer chromatographic behaviour of thirteen anions on plain silica gel and silica gel impregnated with copper sulphate solution has been investigated in aqueous-organic solvents containing acetone, some of which have achieved reliable and reproducible separations. The effect of copper sulphate concentration on the mobility of anions has been examined. The results obtained on plain silica gel have been compared with those obtained on copper sulphate impregnated layers. The impregnated layers dramatically change the selectivity and permit separations not possible on untreated silica. Aqueous sodium chloride-acetone (9∶1) and ammonium hydroxide-acetone (9∶1) were the most effective solvent systems for differential migration of anions. Better results in terms of clarity of detection and compactness of spots were found with HCOOH-acetone as compared to HCl-acetone. The effect of anion loading on R_F values has been investigated and identification limits on impregnated layers determined.     

Sandwich complexes based on the "all-metal" Al4 2- aromatic ring

We report on novel sandwichlike structures [Al(4)MAl(4)](q-) (q=0-2 and M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W) based on the recently synthesized all-metal aromatic Al(4)(2-) square ring. The sandwichlike structures have two aromatic tetraaluminum square rings which trap a transition-metal cation from either the first, second, or third row. The stability of the anionic sandwichlike complexes towards electron detachment is discussed, and addition of alkali cations is found to stabilize the 2- charged complexes, preventing spontaneous electron detachment. Once the sandwichlike complexes are formed, the Al(4)(2-) square properties remain nearly unchanged; this fact strongly supports the hypothesis that in these complexes the Al(4)(2-) square rings remain aromatic.     

Liquid chromatography with and of platinum complexes

Summary Reversed-phase, high-performance liquid chromatography (HPLC) on chemically bonded C₁₈-phases with acetonitrile-water mobile phases, contianing platinum complexes like Zeise's salt C₂H₄PtCl₃, the amine derivative C₂H₄–PtCl₂–NH₂–CH(CH₃)–C₆H₅ or the amino acid compound C₂H₄–PtCl–OOC–CH(N(CH₃)₂)–C₆H₅ by analogy with argentation chromatography, was used to increase selectivity for the separation of various types of olefins, amines and heterocyclic compounds. On the other hand, normal-phase adsorption chromatography on silica with n-heptane, dichloromethane and n-propanol mobile phases proves to be an ideal tool for the analytical and preparative separation of diastereomeric platinum complexes of olefins, introduced by Gil-Av, that can be easily preparedin vitro, by the reaction of C₂H₄–PtCl–OOC–CH(N(CH₃)₂)–C₆H₅ with optically active olefins in CH₂Cl₂. The preparation of the intitial complex as well as its application to the separation of several interesting types of enantiomeric olefins is described and discussed. The number and amount of separable diastereomers formed by the above reaction is strongly influenced by sterical effects. By comparison of the chromatographic pattern of either racemic or partly racemic mixtures, it is possible to decide, which peaks belong to one or the other enantiomeric form of the olefin.