Convenient synthesis of multifunctional EDTA-based chiral metal chelates substituted with an S-mesylcysteine

We describe the synthetic route to ethylenediaminetetraacetic acid (EDTA) derivatives that can be attached to surface-exposed thiol functional groups of cysteine residues in proteins, via a methylthiosulfonate moiety that is connected in a stereochemically unique way to the C-1 carbon atom of EDTA. Such compounds can be used to align proteins in solution without the need to add liquid crystalline media, and are, therefore, of great interest for the NMR spectroscopic analysis of biomolecules. The binding constant for the paramagnetic tag to lanthanide ions was determined by measuring luminescence. For the Tb(+3)-ligand complex, a K(b) value of 6.5 x 10(17) M(-1) was obtained. This value is in excellent agreement with literature values for the related EDTA compound. In addition, it could be shown that there is no significant reduction in the luminescence intensity upon addition of a 10(4) excess of Ca2+ ions, indicating that this paramagnetic tag is compatible with buffers containing high concentrations of divalent alkaline earth ions.     

Studies on nucleation from solution of some analytically important metal chelates

The combination of precipitation from homogeneous solution and Vonnegut's droplet technique is employed in the study of nucleation from solution of bis(1,2-cyclohexanedionedioxunato)Ni(II), bis(1,2-cycloheptanedionedioximato)Ni(II), bis(1,2-cyclohexanedionedioximato)Pd(II) and bis(1,2-cycloheptanedionedioximato)-Pd(II). Values of the kinetic constant, surface energy, critical radius and the number of molecules per critical nucleus are calculated and discussed in terms of the limitations of the classical theory of nucleation when applied to crystal nucleation from aqueous solutions of electrolytes.     

Biligand metal chelates of 1,10-phenanthroline and several salicyclic acid derivatives in solution

Summary Mixed ligand complexes of copper(II), zinc(II), nickel(II) and cobalt(II) ions involving 1,10-phenanthroline (phen) as primary and 3,5-dinitrosalicylic acid (dnsa), 5-nitrosalicylic acid (nsa), 5-chlorosalicylic acid (csa) and 3,5-dibromosalicylic acid (dbsa) as secondary ligands in solution have been investigated potentiometrically [25°, µ = 0.1 M [NaClO₄], medium 50% v: v aqueous ethanol]. The stability order of mixed ligand complexes with respect to the metal ions obeys the natural order: cobalt(II) < nickel(II) < copper(II) > zinc(II). The stabilities of the heterometal chelates have been compared with the corresponding homometal chelates of the secondary ligands and have been interpreted in terms of metal-ligand effects and coulombic interactions between various ligand anion species present.     

Chromatography of metal chelates

Summary The chromatographic behavior of metal bis(ethoxyethyl)dithiocarbamate was investigated. The chelates of 14 elements (V, Cr, Co, Ni, Cu, Zn, Se, Mo, Cd, Te, Hg, Tl, Pb and Bi) could be preconcentrated from water with an on-line system and were shown to be suitable for C₁₈-reversed-phase liquid chromatography. A quaternary solvent mixture with admixture of a surfactant was used as eluent, UV-detection was performed at 254 nm. Thermostating the column to 40° C resulted in a significant increase in chromatographic resolution and in a decrease of analysis time. The recovery of the chelates from the aqueous solutions as well as reproducibility of the results are very sensitive to pH changes.

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Chromatographie von MetallchelatenXI. Spurenanalyse von Cadmium, Cobalt, Kupfer, Quecksilber und Nickel in Wasser mittels Bis(ethoxyethyl)dithiocarbamat als Reagens für die RP C₁₈-HPLC mit photometrischer Detektion

Zusammenfassung Das chromatographische Verhalten von Metall-bis(ethoxyl)-dithiocarbamaten wurde untersucht. Die Chelate von 14 Elementen (V, Cr, Co, Ni, Cu, Zn, Se, Mo, Cd, Te, Hg, Tl, Pb und Bi) wurden aus Wasser angereichert und anschließend direkt mittels RP C₁₈-Flüssig-Chromatographie bestimmt. Als mobile Phase diente ein quaternäres Lösungsmittelgemisch, dem ein Tensid zugesetzt wurde; Detektion fand bei 254 nm statt. Eine bemerkenswerte Steigerung der chromatographischen Auflösung sowie eine Verkürzung der Analysenzeit ergab sich aus der Thermostatisierung der Säule auf 40° C. Die Wiederfindungsrate der Chelate in wäßriger Lösung als auch die Reproduzierbarkeit der Ergebnisse wird stark durch Änderungen des pH-Werts beeinflußt.

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Part X: Häring N, Zell M, Ballschmiter K (1981) Fresenius Z Anal Chem 305:285–286

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Herrn Prof. Dr. K. H. Lieser zum 60. Geburtstag gewidmet Partly presented at the 15th International Symposium on Chromatography, Nürnberg, October 1–5, 1984     

Symmetry of metal chelates

Is a metal chelate symmetric, with the motion of the metal described by a single-well potential, or is it asymmetric, in a double-well potential? For hydrogen, this is the familiar question of the symmetry of a hydrogen bond. The molecular symmetry of MLn complexes (M = Li, Na, K, Al, Pd, Rh, Si, Sn, Ge, Sb, etc.; L is the anion of 3-hydroxy-2-phenylpropenal) in solution is now probed with the method of isotopic perturbation of equilibrium. A statistical mixture of 3-hydroxy-2-phenylpropenal-d0, -1-d, and -1,3-d2 was synthesized and converted to various metal complexes. Some complexes show two aldehydic signals, which means that their ligands are monodentate. For LiL, NaL, and KL, the 13C NMR isotope shifts, delta CH(D) - delta CH(H), for the aldehydic CH groups are small and negative, consistent with L- being a resonance hybrid. They are small and positive for AlL3, PdL2, Rh(CO)2L, SiX3L, SiL3+X-, (CF3)3GeL, SbCl4L, (EtO)4TaL, and (EtO)4NbL. The positive isotope shifts are unusual, but since they are small and temperature independent, they are intrinsic and indicate that these metal chelates are symmetric, as expected. Large positive isotope shifts, up to 400 ppb, are observed for Ph3GeL, Me3GeL, Ph2GeL2, Bu3SnL, and Ph4SbL. However, it is likely that these are monodentate complexes undergoing rapid metal migration, as judged from the X-ray crystal structures of Ph3SnL and Ph4SbL. NMR experiments indicate an intermolecular mechanism for exchange, which may be a biomolecular double metal transfer. It is remarkable that the isotope shifts in these five complexes demonstrate that they are asymmetric structures, even though they appear from other NMR evidence to be symmetric chelates.     

The thermal properties of some metal complexes of diethyldithiocarbamic acid new volatile metal chelates

The cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and mercury(II) complexes of diethyldithiocarbamic acid were prepared and their thermal properties determined by TG, DTA, and high temperature reflectance spectroscopy. It was found that the copper(II), nickel(II), and zinc(II) chelates were completely volatile and thus represent a new class of volatile metal chelates. Vapor pressure measurements were made on four of the metal complexes; heats of vaporization ranged from 9.3±0.2 kcal/mole for Na[Co(DDC)₃] to 24.2±0.6 kcal/mole for Zn(DDC)₂.

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Zusammenfassung Es wurden die Komplexe von Kobalt(II), Nickel(II), Kupfer(II), Zink(II), Cadmium(II), Silber(I) und Quecksilber(II) mit Diäthyldithiokarbaminsäure hergestellt und ihre thermischen Eigenschaften durch Thermogravimetrie, Differentialthermoanalyse und Hochtemperatur Reflexions Spektroskopie untersucht. Man fand, daß die Kupfer(II)-, Nickel(II)- und Zink(II)-Komplexe vollständig verflüchtigen. Sie stellen eine neue Sorte flüchtiger Metallchelate dar. Dampfdruckmessungen wurden an vier der Komplexe unternommen. Die Verdampfungswärmen liegen zwischen den Werten von 9.3±0.2 Kcal/Mol für Na[Co(DDC)₃] bis 24.2±0.6 Kcal/Mol für Zn(DDC)₂.

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Résumé On a préparé les complexes de cobalt(II), nickel(II), cuivre(II), zinc(II), cadrnium(II), argent(I) et mercure(II) avec l'acide diéthyle-dithiocarbaminique et étudié leurs propriétés thermiques par TG, ATD et spectroscopie de reflexion à haute température. On a trouvé que les complexes de cuivre(II), nickel(II) et zinc(II) volatilisent parfaitement; ils représentent une nouvelle sorte de chélates métalliques volatiles. On a fait des mesures de pression de vapeur sur quatre de ces complexes. Les valeurs des chaleurs de vaporisation s'étalent de 9.3±0.2 kcal/mole pour Na[Co(DDC)₃] jusqu'à 24.2±0.6 kcal/mole pour Zn(DDC)₂.

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[II], [II], [II], [II], [II], [I] [II] , . , [II], [II] — . ë -; 9,3±0,2 / Na[Co(DDC)₃] 24,2±0,6 / Zn[DDC]₂.

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The partial support of this work by the U. S. Air Force, Air Force Office of Scientific Research, through Grant No. AF-AFOSR 69-1620, is gratefully acknowledged. One of us (G. D'A.) wishes to thank the National Research Council of Italy, Rome, Italy, for financial support.     

Mass-spectrometric determination of metal chelates

Summary A method has been developed for the determination of copper as copper acetylacetonate, making use of the copper-65 labelled chelate as internal standard. The accuracy and reproducibility in the nanogram range are comparable with those of the ligand labelling method (2% relativ). The method can be easily extended to the determination of other polyisotopic metals of which an enriched stable isotope is obtainable.

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Massenspektrometrische Bestimmung von MetallchelatenII. Quantitative Bestimmung von ng-Mengen Kupfer mit Hilfe der Isotopenverdünnungsmethode

Zusammenfassung Ein Verfahren zur Bestimmung von Nanogramm-Mengen Kupfer als Kupfer-Acetylacetonat unter Verwendung der Isotopenverdünnungsmethode mit angereichertem Kupfer-65 als Leitisotope wird beschrieben. Genauigkeit und Reproduzierbarkeit sind vergleichbar mit dem Ligandenmarkierungsverfahren (2% relativ). Das Verfahren kann leicht ausgebaut werden zur Bestimmung anderer Metalle, falls mehr als ein stabiles Isotop vorhanden ist.

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This investigation was supported in part by the Netherlands Foundation for Chemical Research (S.O.N.) with financial aid from the Netherlands Organization for the Advancement of Pure Research (Z.W.O.).     

The chromatography of metal chelates

Summary The acyl substituents of N,N-disubstituted N'-acylthioureas have a significant influence on the polarity of the chelates formed. A considerable decrease in the stability of the complexes is observed changing from aromatic to aliphatic acyl substituents. In order to separate the acylthiourea complexes, high performance thin-layer chromatography (HPTLC) methods have been used, whereby both standard methods, adsorption chromatography on silicagel layers and RP-chromatography are applicable. The strong UV-absorption properties of acylthiourea chelates allow a very sensitive detection of the separated complexes. By the method described several metals can be determined simultaneously on a migration distance of 2 to 5 cm.     

Mass-spectrometric determination of metal chelates

Zusammenfassung Aus digitalisierten Raman- und Infrarotspekten von 70 Steroiden wurden die Summenspektren der Substanzen mit übereinstimmenden Strukturmerkmalen berechnet. In diesen Spektren sind Banden geringer Standardabweichung dann charakteristisch für ein Strukturmerkmal, wenn sie bei anderen Strukturmerkmalen fehlen. Sie sind dann für die Strukturaufklärung von Substanzen unbekannter Struktur geeignet.

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Raman spectroscopy and molecular structureIII. Selection of characteristic bands of polyatomic molecules by means of a computer

Digitized Raman and infrared spectra of 70 steroids are used for the calculation of summarized spectra of all substances with the same structural details. In these spectra bands with low standard deviation are characteristic for the structural detail if they are absent in the other groups of spectra. They can be used for the elucidation of unknown structures.

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Wir danken Herrn Dipl.-Phys. H. Barentzen für die Aufstellung des Computerprogramms sowie Frl. G. Pannek und Frau E. von Bühlow für die Hilfe bei der Verschlüsselung und Aufbereitung der Daten. — Der Deutschen Forschungsgemeinschaft und dem Landesamt für Forschung, Nordrhein-Westfalen, danken wir für Sachbeihilfen.     

手性氨基酸钛螯合物的合成

用L-对甲苯磺酰氨基酸分别与四氯化钛反应,首次合成了五种L-对甲苯磺酰氨基酸钛化合物。NMR、IR和元素分析数据表明这五种手性钛化合物的结构分别是2a-2d和4,对甲苯磺酰氨基酸钛化合物在惰性气氛中可以保存数周。     

ESR of ortho-dimesitoylbenzene-alkali earth metal chelates

The ESR spectra of rigid glass solutions of biradicals of ortho-dimesitoylbenzene anion and alkali earth ions, were recorded. The zero field splitting parameter D is compared with theoretical values calculated for different interionic distances. The results show that the biradical species should be of the contact type with metal to oxygen distance very close to the sum of the van der Waals radii of oxygen and metal ions.     

Vapor pressure-temperature data for various metal β-diketone chelates

Vapor pressure-temperature data, molar heats of sublimation, and sublimation temperatures are given for 29 metal β-diketone chelates. The chelatcs studied were these of Be(II), Al(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) with acetyl-acetone, acetyltrifluoroacctone, benzoylacetone, benzoyltrifluoroacetone, 2-furoyl-trifluoroacetone, and 2-thenoyltrifluoroacetone. The observed difference in volatilities of the various metal chelatcs of a given ligand is the basis for a suggestion that various mixtures of metal ions can be resolved by a fractional sublimation scheme.     

Annihilation electrogenerated chemiluminescence of mixed metal chelates in solution: modulating emission colour by manipulating the energetics

We demonstrate the mixed annihilation electrogenerated chemiluminescence of tris(2,2′-bipyridine)ruthenium(ii) with various cyclometalated iridium(iii) chelates. Compared to mixed ECL systems comprising organic luminophores, the absence of T-route pathways enables effective predictions of the observed ECL based on simple estimations of the exergonicity of the reactions leading to excited state production. Moreover, the multiple, closely spaced reductions and oxidations of the metal chelates provide the ability to finely tune the energetics and therefore the observed emission colour. Distinct emissions from multiple luminophores in the same solution are observed in numerous systems. The relative intensity of these emissions and the overall emission colour are dependent on the particular oxidized and reduced species selected by the applied electrochemical potentials. Finally, these studies offer insights into the importance of electronic factors in the question of whether the reduced or oxidized partner becomes excited in annihilation ECL.     

Synthesis, chiroptical properties, and solid-state structure determination of two new chiral dipyrrin difluoroboryl chelates

Two new types of optically active BODIPY fluorophores bearing chiral phenyl substituents either at the meso-position or at both external alpha-positions have been synthesized. Their chiroptical properties are strongly dependent both on the position of the chiral group and on the protonation of the chromophore. The solid-state structures of one of the difluoroboryl chelates bearing the chiral phenyl substituent at the meso-position (9a) as well as of the corresponding ligand (8a) and its perchlorate have been determined by X-ray diffraction analysis. These are, to the best of our knowledge, the first crystal structures of a dipyrrin free base and of a dipyrrin salt which have been obtained by X-ray diffraction analysis. Hence, for the first time, the helical structure of a protonated dipyrrin chromophore has been proved experimentally.     

Thermal analysis of some metal n-benzoyl-n-phenylhydroxylamine chelates

The preparation and thermal analysis of the metal chelates of N-benzoyl-N-phenylhydroxylamine (BPHA) with Al(III), Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II) and Zn(II) is discussed. The differential thermal analysis apparatus is described in detail. DTA and TGA curves of BPHA arid the chelates from 25 to 700° in oxygen and in nitrogen are presented.     

Fractional sublimation of various metal b-diketone chelates

The vacuum fractional sublimation of various metal β-diketone chelates was compared with the fractional sublimation of the metal acetylacetonates reported earlier. Characteristic recrystallization temperature zones are reported for a number of metal acetylacetonates, acetyltrifluoroacetonates, hexafluoroacetylacetonates, benzoylacetonates, and benzoyltrifluoroacetonates. The substitution of a trifluoromethyl for a methyl group in the ligand molecule increased the volatility of the corresponding metal chelates, but this increased volatility did not lead to improved separations by fractional sublimation. In particular, the hexafluoroacetylacetonates tended to recrystallize as microcrystals in diffuse zones which extended over much of the sublimation tube and the benzoyltrifluoroacetonates tended to distill rather than sublime, with the liquids flowing down the wall of the tube. The best separations were achieved among the metal acetylacetonates. The chelates studied are generally stable and can be recovered from the sublimation apparatus in near quantitative yields. Separations of mixtures of Be, Mg, and Cr ; Fe, Mg and Al ; and Fe and Al were studied critically. Although the separations were not complete, they compared favorably with some reported gas-chromatographic separations.     

Photoacoustic spectra of some biological metal chelates

Photoacoustic spectra of Ni2+ in three new chelates containing azolo-2,4 pentanedione derivatives have been recorded and analysed in the visible region. The approximate symmetry of Ni2+ has been found to be octahedral. The d-d transitions in the red region show some similarity with those of nickel chloride and nickel acetate. In each case two charge-transfer bands appear in the violet region.