On the relationship between the structures of Cu(II) complexes and their chemical transformations

The experimental activation energies (E ^*) of dehydration of Cu(NH₃)₄(H₂O)SO₄, Cu(en)₂(H₂O)X₂ (X=Cl^?, Br^?), Cu(en)(H₂O)₂SO₄, Cu(py)₂(H₂O)₂SO₄, CuCl₂ · 2H₂O and M ₂ ^I CuCl₄ · 2H₂O (M ^I =NH₄, K, Rb) were obtained from their non-isothermal thermogravimetric curves using the Coats-Redfern method. TheseE ^* values were compared with known data on the structures of the Cu(II) coordination polyhedra in the above complexes. No dependence of theE ^* values was found on either the central atom — released ligand bond length, or the number and lengths of the hydrogen bonds formed by the released water molecules. However, it was found that it is justified to seek some relationship between theE ^* values and the anisotropic temperature factors of the donor atoms of the ligands split off.     

On the relationship between the structures of Cu(II) complexes and their chemical transformations

The thermal dehydration of pentacoordinate complexes [Cu(maleinate)(H₂O)] (I), [Cu₂(citrate) (H₂O)₂] (II) and [Cu(phenoxyacetate)₂(H₂O₃] (III) was investigated and correlated with the structural changes occurring during the dehydration. It was found that the activation parameters of the reactions do not follow the lengths of the split Cu?OH₂ bonds. The lowestE _a and lgA values were found for compound I, the highest ones for compound III. The most expressive changes of the anionic ligand binding mode take place during the dehydration of this compound.     

On the relationship between the structures of Cu(II) complexes and their chemical transformations

The paper deals with the relationship between the crystal and molecular structures of CuSO₄.5 H₂O, CuSO₄.3 H₂O and CuSO₄.H₂O on the one hand, and the stoichiometries of their thermal decompositions on the other. With the use of methods of X ray powder diffractograms, i.r. and electronic spectra, evidence is provided that the intermediates of the thermal decomposition of CuSO₄.5 H₂O have the same crystal and molecular structures as CuSO₄.3 H₂O and CuSO₄.H₂O prepared by other procedures. It is also shown that at temperatures near that of the thermal decomposition, certain, not further identified structural changes take place in CuSO₄.5 H₂O.

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Zusammenfassung Es wird einerseits der Zusammenhang der Kristall- und Molekularstruktur von CuSO₄ · 5H₂O, CuSO₄ · 3H₂O und CuSO₄ · H₂O behandelt und andererseits die Stöchiometrie ihrer thermischen Zersetzung. Mit der Auswertung der Röntgen-Pulverdiffraktogramme, der IR- und Elektronenspektren wurde der Beweis erbacht, da\ die Zwischen-produkte der thermischen Zersetzung von CuSO₄ · 5H₂O dieselben Kristall- und Molekül-strukturen besitzen, wie auf anderen Wegen hergestelltes CuSO₄ · 3H₂O bzw. CuSO₄ · H₂O. Ferner wurde gezeigt, da\ bei Temperaturen in der NÄhe der thermischen Zersetzungstemperatur gewisse, jedoch noch nicht identifizierte StrukturÄnderungen in dem CuSO₄ · 5H₂O stattfinden.

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Résumé L'article examine la corrélation entre les structures cristallines et moléculaires de CuSO₄.5 H₂O, CuSO₄.3 H₂O et CuSO₄.H₂O d'une part et la stoechiométrie de leur décomposition thermique de l'autre. En se servant des méthodes des diffraction des rayons X sur poudre et des spectres infra-rouges et électroniques on montre que les produits intermédiaires de la décomposition thermique de CuSO₄.5 H₂O ont les mÊmes structures cristallines et moléculaires que celles de CuSO₄.3 H₂O et de CuSO₄.H₂O préparées par d'autres procédés. On montre également qu'à des températures proches de celle de la décomposition thermique de CuSO₄. 5H₂O des changements structuraux non encore identifiés ont lieu.

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uSO₄ · 5₂, uSO₄ · ₂ uSO₄ · ₂, — . , , , uSO₄ · 5₂ uSO₄ · ₂ uSO₄ · ₂, . , , uSO₄, · 5₂ , .

     

The relationship between the structures of Cu(II) complexes and their chemical transformations

The paper reports an attempt to correlate the structures of hydrates of copper(II) sulphate with some characteristic features of the kinetics of their thermal decompositions. Non-isothermal thermogravimetric measurements were employed to obtain values of experimental activation energy and entropy for the dehydration of CuSO₄ · 5 H₂O, CuSO₄ · 3 H₂O and CuSO₄ · H₂O. The values ofE ^* andΔS ^* for the dehydration of CuSO₄ · 3 H₂O were found to be only little affected by the mode of preparation of this compound. On the other hand, the values ofE ^* andΔS ^* for the dehydration of CuSO₄ · ·H₂O are strongly dependent on whether this compound was prepared by thermal decomposition of CuSO₄ · 5 H₂O or CuSO₄ · 3 H₂O, or by crystallization from solution. As regards the crystalline hydrates of copper(II) sulphate, the greatest energetic hindrance for dehydration was observed for CuSO₄ · 3 H₂O. The experimental results are also discussed with respect to the present opinions concerning the possibilities of using thermal analyses to obtain information on the relationship between the structures and reactivities of solids.     

The relationship between the structures of Cu(II) complexes and their chemical transformations

The study of the thermal dehydration of the compounds CuX2.nH₂O, where X^– were formate, salicylate or phtalate anions, was performed, including the observations of structural changes of compounds during their decomposition. It is shown that the dehydration of copper(II) formate tetra- and dihydrates is accompanied by significant changes in the bonding of the formato groups and remaining water molecules. Two structurally different modifications of Cu(HCOO)₂.2H₂O were prepared, the structure differences are clearly demonstrated in their decomposition stoichiometry. The dehydration of copper formate hydrates was found to be controlled by chemical reaction on the phase boundary. The dehydration of the copper salicylate tetrahydrate and copper phtalate monohydrate is accompanied by the structural changes of the whole compounds, as well, however these processes are diffusion or nucleation controlled.

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Zusammenfassung Es wurde die thermische Dehydratation der Verbindungen CuX₂.nH₂O mit dem Formiat-, Salicylat- und Phthalatanion als X^– unter gleichzeitiger Beobachtung eventueller Strukturveränderungen dieser Verbindungen während der Dehydratation untersucht. Es wird gezeigt, dass die Dehydratation von Kupfer(II)-formiat Tetrabzw. Dihydrat von einer eindeutigen Veränderung der Bindungsverhältnisse der Formiatgruppen und der verbleibenden Wassermoleküle begleitet wird. Es wurden zwei strukturell verschiedene Modifikationen von Cu(HCOO)₂.2H₂O hergestellt, die Strukturunterschiede zeigen sich deutlich in der Stöchiometrie ihrer Zersetzung. Die Dehydratation von Kupferformiathydraten wird durch die chemische Reaktion an der Phasengrenze kontrolliert. Die Dehydratation von Kupfersalicylat Tetrahydrat und Kupferphthalat Monohydrat wird von einer Strukturveränderung des ganzen Moleküles begleitet, unabhängig davon, ob der Vorgang durch die Diffusion oder Kernbildung bestimmt wird.

     

The relationship between the structures of Cu(II) complexes and their chemical transformations

The paper presents the results of a study of M ₂ ^I M ^II(SO₄)₂ compounds withM ^I= K, Rb, Cs or Tl, andM ^II=Cu or Ni, in the interval from room temperature to the melting temperature. All the compounds studied show endo- or exothermic excursions in their DTA curves, corresponding to phase transitions connected with colour changes of the compounds. For M ₂ ^I Cu(SO₄)₂, whereM ^I is K or Tl, several modifications could be prepared at laboratory temperature, probably distortion isomers. No modifications of this type could be prepared, however, for M ₂ ^I Ni(SO₄)₂ compounds.

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Zusammenfassung Die Ergebnisse einer Untersuchung von M ₂ ^I M ^II(SO₄)₂-Verbindungen Cs, Tl;M ^II=Cu, Ni) im Temperaturbereich von Raum- bis Schmelztemperatur werden beschrieben. Alle untersuchten Verbindungen zeigen in ihren DTA-Kurven mit Farbänderungen einhergehende, durch Phasenumwandlungen bedingte endo- und exotherme Peaks. Bei Laboratoriumstemperatur konnten verschiedene Modifikationen von M ₂ ^I Cu(SO₄)₂ (mitM ^I gleich K oder Tl) hergestellt werden, wobei es sich wahrscheinlich um Distorsionsisomere handelt. Keine Modifikationen dieses Typs konnten jedoch für M ₂ ^I Ni(SO₄)₂ erhalten werden.

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M ₂ ^I M ^II(SO₄)₂, ¹-, Rb, Cs Tl, aM ¹¹-Cu Ni, . - -, , . M ₂ ^I Cu(SO₄)₂, ¹- l, , , , . , M _i ² Ni(SO₄)₂ .

     

The relationship between the structures of Cu(II) complexes and their chemical transformations

The thermal dehydration of the compounds M ₂ ^I [M^II(H₂O)₆](SeO₄)₂, where M^I=NH₄, K, Rb, Cs and Tl, and M=Cu and Ni, was studied in order to correlate the course of the decomposition with the known crystal structures. It was found that the stoichiometry of the reactions is the same as that established for the analogous sulphato compounds of Cu(II) and Ni(II), respectively. Because of the discrepancies between the room-temperature crystal structures and the observed decomposition stoichiometries, high-temperature powder diffractograms were taken. These indicated structural changes of the copper(II) compounds during heating. The powder patterns for different structure changes were calculated and compared with the experimental ones. It was shown that during the heating two axial CuH₂O bonds are shortened and two equatorial bonds are lengthened. The observed decomposition stoichiometry is compatible with the formation of four nearly equal Cu-H₂O bonds. The activation energies (E^*) and pre-exponential factors (log A) for the first dehydration reaction of the Cu(II) compounds display the following sequence of M^I: Tl > Rb > NH₄ > K, and they are the higher, the shorter the split equatorial Cu(II) bonds. For the compounds of Ni(II) the sequence of E^* and log A values is K > Tl > NH₄ > Rb > Cs.

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Zusammenfassung Zur Aufklärung des Zusammenhanges zwischen dem Zersetzungsweg und der bekannten Kristallstruktur wurde die thermische Dehydration der Verbindungen M ₂ ^I [M^II(H₂O)₆](SeO₄)₂ mit M^I=NH₄, K, Rb, Cs and Tl sowie mit m^II=Cu und Ni untersucht. Man fand für diese Reaktion die gleiche Stöchiometrie wie für die analogen Sulfatverbindungen von Cu(II) bzw. Ni(II). Wegen des Widerspruches zwischen der Kristallstruktur bei Raumtemperatur und der festgestellten Stöchiometrie der Zersetzungsreaktion wurden auch Pulverdiffraktionsaufnahmen bei höheren Temperaturen angefertigt. Bei Cu(II)-Verbindungen konnte während des Erhitzens eine Strukturänderung festgestellt werden. Für verschiedene Strukturänderungen wurden Pulveraufnahmen berechnet und mit den experimentellen verglichen. Es konnte gezeigt werden, da sich während des Erhitzens zwei axiale Cu-H₂O-Bindungen verkürzen und zwei äquatoriale Bindungen strecken. Die beobachtete Zersetzungsstöchiometrie entspricht der Bildung von vier anänhernd gleichen Cu-H₂O-Bindungen. Die Aktivierrungsenergie (E^*) und der präexponentielle Faktor (log A) und der ersten Dehydratationsreaktion der Cu(II)-Verbindungen sinken in folgender Reihenfolge für M^I:Tl, Rb, NH₄, K und sind umso größer, je kürzer die gespaltenen äquatorialen Cu(II)-Bindungen sind. Für Ni(II)-Verbindungen nehmen E^* und log A in folgenden Reichenfolge ab: K, Tl, NH₄, Rb, Cs.

     

The relationship between the structures of Cu(II) complexes and their chemical transformations

The structures of compounds M ₂ ^I M^II(SEO₄)₂ (M^I=K, Tl; M^II=Cu and Ni), were studied using IR, electronic and EPR spectra. The results indicate a hexacoordination of both central atoms, and a bridging function of selenato groups, the mode of their coordination varies with M^I and M^II. The compound Tl₂Cu(SeO₄)₂ was prepared also in the amorphous glassy form, although with partial decomposition. It is presumed that in the homogeneous smaragd-green material -Cu-O-Cu-, -Cu-OSeO₂-Cu- and -Cu-OSeO₃-Cu- bridges are present simultaneously. The course of the thermal decomposition of the studied compounds depends on the nature of the M^I and M^II cations. According to powder X-ray patterns, the decomposition products do not contain individual oxides. Nearly complete removal of selenium was observed in the decomposition of hydrated ammonium double selenates of Ni(II) and Cu(II).

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Zusammenfassung Mittels IR-, Elektronen- und EPR-Spektren wurden die Strukturen der Verbindungen M ₂ ^I M^II (SeO₄)₂ mit M^I=K und Tl sowie M^II=Cu and Ni bestimmt. Die Ergebnisse zeigen eine Hexakoordination beider Zentralatome und eine Brückenfunktion der Selenatgruppen, deren Koordination sich mit M^I und M^II ändert. Die Verbindung Tl₂Cu(SeO₄)₂ wurde, wenn auch unter geringen Zerfalles, auch in einer amorphen Glasform hergestellt. Es wird angenommen, daß in den Smaragdgrün-Stoffen gleichzeitig-Cu-O-Cu-, -Cu-OSeO₂-Cu- und -Cu-OSeO₃-Cu- Brücken vorkommen. Der Verlauf der thermischen Zersetzung der untersuchten Verbindungen hängt von der Art der M^I und M^II-Kationen ab. In Bezugnahme auf Röntgenpulverdiffraktionsaufnahmen enthalten die Zersetzungsprodukte keine getrennten Oxide. Beim Zerfall von hydratierten Ammoniumdoppelselenaten von Ni(II) und Cu(II) wurde eine fast vollständige Abgabe von Selen beobachtet.

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M ₂ ^I Mⁱⁱ(SeO₄)₂, ⁱ — , , ⁱⁱ , - , . , - ^{i ii}. Tl₂Cu(SeO₄)₂ , . , ----, --OSeO₂- -Cu-OSeO₃-u-. ^{i ii}. , . .

     

The relationship between the structures of Cu(II) complexes and their chemical transformations

The paper presents the results of a study of the course of thermal decomposition of complexes Cu(NCO)₂L₂ and Cu(LNCO)₂, withL=pyrazole, 3,5-dimethylpyrazole, 3,4,5-trimethylpyrazole and indazole. The DTA curves of Cu(NCO)₂L₂ show exothermic excursions somewhat below the decomposition temperatures, corresponding to an inner complex nucleophilic addition of a carbon atom (from an NCO group) to the imine nitrogen atom of a pyrazole ligand. In this reaction the carbamoylpyrazolate anion is formed, coordinated to Cu(II). For these reactions the DSC method yielded the followingH values: –12.80 kJ mol^–1 (L=pyrazole), –8.15 kJ mol^–1 (L=3,5-dimethylpyrazole), –19.49 kJ mol^–1 (L=3,4,5-trimethylpyrazole) and –11.59 kJ mol^–1 (L=indazole). The course of thermal decomposition for Cu(NCO)₂L₂ after the nucleophilic addition is the same as for Cu(LNCO)₂. The structure differences between the distortion isomers of Cu(NCO)₂L₂ and Cu(LNCO)₂ were manifested in the decomposition temperatures and, in some cases, also in the stoichiometry of the decomposition reactions.

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Zusammenfassung Der Verlauf der thermischen Zersetzung der Komplexe Cu(NCO)₂L₂ und Cu(LNCO)₂ mitL= Pyrazol, 3,5-Dimethylpyrazol, 3,4,5-Trimethylpyrazol und Indazol wurde untersucht. Die DTA-Kurven von Cu(NCO)₂L₂ zeigen etwas unterhalb der Zersetzungstemperaturen exotherme Effekte, die einer inneren komplexen nukleophilen Addition eines Kohlenstoffatoms (von einer NCO-Gruppe) an das Iminstickstoffatom eines Pyrazol-Liganden entsprechen. In dieser Reaktion wird das an Cu(II) koordinativ gebundene Carbamoylpyrazolat-Anion gebildet. Für diese Reaktionen wurden mit der DSC-Methode folgendeH-Werte erhalten: –12,80 kJ· mol^–1 (L= Pyrazol), –8,15 kJ·mol^–1 (L= 3,5-Dimethylpyrazol), –19,49 kJ·mol^–1 (L=3,4,5-Trimethylpyrazol) und –11,59 kJ·mol^–1 (L= Indazol). Nach der nukleophilen Addition zeigt Cu(NCO)₂L₂ den gleichen thermischen Zersetzungsverlauf wie Cu(LNCO)₂. Die Strukturunterschiede zwischen den Distortionsisomeren von Cu(NCO)₂L₂ und Cu(LNCO)₂ manifestieren sich in der Zersetzungstemperatur und, in einigen Fällen, auch in der Stöchiometrie der Zersetzungsreaktion.

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Cu(NCO₂L₂ Cu(LNCO)₂, L=, 3,5- , 3,4,5- . Cu(NCO)₂L₂ , ( NCO) . -, . H: : –12,80 /, 3,5- — –8,15 /, 3,4,5- –19,49 / — – 11,59 /. , Cu(LNCO)₂. — .

     

The relationship between the structures of Cu(II) complexes and their chemical transformations: VII

The thermal decompositions of Cu(en)₂(NCS)X. where X^–=Cl^–, Br^–, NO ₃ ^– , BF ₄ ^– and ClO ₄ ^– , have been studied in comparison with the courses of Cu(en)₂(SCN)₂ and Cu(en)₂X₂ decomposition. It is shown that the presence of the thiocyanate group in the complexes Cu(en)₂(NCS)X is the most important factor in the decomposition course, in agreement with the fact that the anions X^– are not coordinated. or are only semicoordinated. Significant differences were found in the courses of thermal decomposition of two forms of Cu(en)₂(NCS)(BF₄) differing in the structure of their coordination polyhedra.

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Zusammenfassung Die thermische Zersetzung von Cu(en)₂(NCS)X (X=Cl Br, NO₃, BF₄ und ClO₄) wurde untersucht und mit der von Cu(en₂(SCN)₂ und Cu(en)₂X₂ verglichem. Der den Verlauf der Zersetzung entscheidend bestimmende Faktor isi die Anw esenheit der Thiocyanat-Gruppe in den Cu(en)₂(NCS)X-Komplexen, was in Übereinstimmung damit steht,. daß die Anionen X nicht oder nur teilweise koordiniert sind. Es wurden signifikante Unterschiedeim Verlauf der thermischen Zersetzung von zwei sich in der Struktur ihrer Kordinationspolyeder unter-, heidenden Formen von Cu(en)₂(NCS)(BF₄) gefunden.

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Cu(en)₂(NCS)X (X^–=Cl^–, Br^–, NO ₄ ^– , NO ₃ ^– , BF₄ ClO₄, Cu(en)₂(SCN)₂ Cu(en)₂(X)₂. , Cu(en)₂(NCS)X X Cu(en) (NCS)BF₄ i .

     

The relationship between the structure of Cu(II) complexes and their chemical transformations: VI

Data on the activation energies of dehydration of the complexes [Cu(en)₂(H₂O)]X₂, [Cu(, -bipy)₂(H₂O)]S₂O₆ and [Cu(o-phen)₂(H₂O)]X₂ were gained by means of dynamic TG, and theH values of the same reactions by DSC. The results were correlated with known data on the crystal structures of the studied complexes. No significant differences betweenE and/orH values were found for tetragonal pyramidal and trigonal bipyramidal complexes. For complexes with sufficiently exactly solved crystal structures, the activation energies increase with decreasing values of the anisotropic temperature factors (in the Cu-OH₂ bond directions). Activation energy values are also influenced by the type of structural changes accompanying the formation of the intermediate of thermal decomposition.

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Zusammenfassung Werte für die Aktivierungsenergien bzw.H-Werte der Dehydratisierung der Komplexe [Cu(en)₂(H₂O)]X₂, [Cu(,-bipy)₂(H₂O)]S₂O₆ und [Cu(o-phen)₂(H₂O)] wurden durch dynamische TG bzw. DSC erhalten. Die Ergebnisse wurden mit bekannten Daten über die Kristallstruktur der untersuchten Komplexe verglichen. Keine signifikanten Unterschiede zwischenE ^*- und/oderH-Werten wurden für tetragonal-pyramidale und trigonal-bipyramidale Komplexe gefunden. Die Untersuchung von Komplexen mit genügend genau bekannter Kristallstruktur hat ergeben, daß die Aktivierungsenergie mit abnehmenden Werten des anisotropen Temperaturfaktors (in der Cu-OH₂-Bindungsrichtung) abnimmt. Die Aktivierungsenergie wird auch durch den Typ der die Bildung von intermediären thermischen Zersetzungsprodukten begleitenden strukturellen Veränderungen beeinflußt.

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H [u()₂(H₂O)]X₂, [Cu(, -)₂(H₂O)]S₂O₆ [Cu(o-)₂(₂)]₂. - . - - - E H. - - Cu-OH₂. - , - .

     

On the relationship between the structures of CuII complexes and their chemical transformations

The thermal decomposition of the complexes M ₂ ^I Cu(SO₄)₂ · 6 H₂O and M₂Ni(SO₄)₂ · · 6 H₂O (M^I=NH₄, K, Rb, Tl) containing the complex cation M^II(H₂O)₆ ²+ (M^Il = =Cu, Ni) was studied. The values of the experimental activation energyE obtained for the dehydration reactions of both complex cations were found to be influenced in different ways by the outer-sphere cations present. It was therefore concluded that the activation energy of the decomposition of Cu(H₂O)₆ ²⁺ depends on the degree of tetragonal distortion of this cation, which increases with the ionic radius of cation M^I. TheΔH values of the studied reactions depend less on the structures of the coordination polyhedra.     

On the relationship between the structures of Cu(II) complexes and the course of their thermal decomposition

Thermal decomposition of [Cu₄O(Cl+Br)₆(OPPh₃)₄], starts at temperatures about 200°C. The decomposition proceeds in several steps. The intermediate formed in the first decomposition step (weight loss 2–4%) is a new crystalline phase with slightly different structure but with preserved central unit Cu₄O. The only crystalline phases found in the further decomposition products was CuBr in all cases when the bromine atoms were present, the presence of CuCl was only observed at the decomposition of the hexachlorocomplex.     

X-ray and solution structures of Cu(II) GHK and Cu(II) DAHK complexes: influence on their redox properties

The Gly‐His‐Lys (GHK) peptide and the Asp‐Ala‐His‐Lys (DAHK) sequences are naturally occurring high‐affinity copper(II) chelators found in the blood plasma and are hence of biological interest. A structural study of the copper complexes of these peptides was conducted in the solid state and in solution by determining their X‐ray structures, and by using a large range of spectroscopies, including EPR and HYSCORE (hyperfine sub‐level correlation), X‐ray absorption and ¹H and ¹³C NMR spectroscopy. The results indicate that the structures of [Cu^II(DAHK)] in the solid state and in solution are similar and confirm the equatorial coordination sphere of NH₂, two amidyl N and one imidazole N. Additionally, a water molecule is bound apically to Cu^II as revealed by the X‐ray structure. As reported previously in the literature, [Cu^II(GHK)], which exhibits a dimeric structure in the solid state, forms a monomeric complex in solution with three nitrogen ligands: NH₂, amidyl and imidazole. The fourth equatorial site is occupied by a labile oxygen atom from a carboxylate ligand in the solid state. We probe that fourth position and study ternary complexes of [Cu^II(GHK)] with glycine or histidine. The Cu^II exchange reaction between different DAHK peptides is very slow, in contrast to [Cu^II(GHK)], in which the fast exchange was attributed to the presence of a [Cu^II(GHK)₂] complex. The redox properties of [Cu^II(GHK)] and [Cu^II(DAHK)] were investigated by cyclic voltammetry and by measuring the ascorbate oxidation in the presence of molecular oxygen. The measurements indicate that both Cu^II complexes are inert under moderate redox potentials. In contrast to [Cu^II(DAHK)], [Cu^II(GHK)] could be reduced to Cu^I around ?0.62 V (versus AgCl/Ag) with subsequent release of the Cu ion. These complete analyses of structure and redox activity of those complexes gave new insights with biological impact and can serve as models for other more complicated Cu^II–peptide interactions.     

Phenyl-cyclohexyl enaminoketone ligands and their Cu(II) complexes

The liquid crystalline properties of 1-(alkylamino)-3-[(4'-hexyl-trans-cyclohexyl-4'-phenyl]-prop-1-en-3-one-s, from methyl to octadecyl, and their copper (II) complexes have been examined by optical, DSC, X-ray and EPR methods. The compounds are enantiotropic nematogens except those having the shortest and the longest terminal chains. Short chains promote the S_A phase in both ligands and complexes, whereas long chains promote S_C and crystal H phases for the ligands or S_A and S_C phases for the complexes. A partly bilayer smectic A_d phase is observed from ligands terminated with short non-polar substituents. Direct isotropisation from the crystal H phase for some of the compounds, as well as other phase transitions have been studied. The molecular shape of the complexes and the organization of their mesomorphic phases are discussed, based on the refractive indices and X-ray data.     

The relationship between the structures of Cu(ii) coordination compounds and their thermal decomposition

A study was made of the influence of the composition of the Cu(II) coordination sphere on the course of the thermal decomposition of the complexes Cu₄O(X+Y)₆L₄, whereX andY were Cl and Br, andL was piperidine or morpholine. The tetrahedral unit Cu₄O with the oxygen atom in its centre was found to be the thermally weakest part of the complex. The decomposition temperatures of the complexes were strongly influenced by the anionsX andY and by the ligandL. The temperature at which decomposition started was found to be the lower, the more chloride anions were substituted by bromide anions. The complexes containing piperidine as ligandL exhibited higher decomposition temperatures than those with morpholine as ligand. The decompositions of all the studied complexes were accompanied by redox reactions. The only compounds identified among the decomposition intermediates by X-ray diffraction were copper(I) halides. Copper(I) bromide underwent oxidation on further heating and a mixture of CuO and CuBr was obtained as the final decomposition product.

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Zusammenfassung Bei der thermischen Zersetzung von Komplexen der Formel Cu₄O(X+Y)₆L₄ mitX,Y=Cl bzw. Br undL= Piperidin oder Morpholin wurde der Einfluß der Zusammensetzung der Cu(II)-Koordinationssphäre auf den Verlauf der thermischen Zersetzung untersucht. Als thermisch schwächstes Glied des Komplexes wurde die tetraedrische Einheit Cu₄O mit dem Sauerstoffatom im Zentrum befunden. Die Zersetzungstemperaturen der Komplexe werden durch die AnionenX undY sowie durch die LigandenL wesentlich beeinflußt. Die Temperatur, bei der die Zersetzung einsetzt liegt um so niedriger, je mehr Chloridanionen durch Bromidanionen ersetzt werden. Komplexe mit Piperidin als Ligand zeigen höhere Zersetzungstemperaturen als mit dem Ligand Morpholin. Die Zersetzung aller Komplexe ist von Redoxreaktionen begleitet. Die einzigen Verbindungen, die unter den Zersetzungsprodukten mittels Röntgendiffraktion identifiziert wurden, waren Kupfer(I)-halogenide. Kupfer(I)-bromid unterliegt bei weiterem Erhitzen einer Oxidation und man erhält letztendlich ein Gemisch aus CuO und CuBr als Zersetzungsprodukt.

     

Phenyl-cyclohexyl enaminoketone ligands and their Cu(II) complexes

Abstract

The liquid crystalline properties of 1-(alkylamino)-3-[(4″-hexyl-trans-cyclohexyl-4′-phenyl]-prop-1-en-3-one-s, from methyl to octadecyl, and their copper (II) complexes have been examined by optical, DSC, X-ray and EPR methods. The compounds are enantiotropic nematogens except those having the shortest and the longest terminal chains. Short chains promote the S_A phase in both ligands and complexes, whereas long chains promote S_C and crystal H phases for the ligands or S_A and S_C phases for the complexes. A partly bilayer smectic A_d phase is observed from ligands terminated with short non-polar substituents. Direct isotropisation from the crystal H phase for some of the compounds, as well as other phase transitions have been studied. The molecular shape of the complexes and the organization of their mesomorphic phases are discussed, based on the refractive indices and X-ray data.     

Mixed salicylaldehydato-acetato complexes of Cu(II) and their reactivity

Bis(salicylaldehydato) Cu(II), Cu(sal)₂, reacts with haloacetic acids RCO₂H(RCF₃, CCl₃, CHCl₂ or CH₂Cl) to give the mixed ligand complexes (RCO₂)Cu(sal). They have subnormal magnetic moments with the exception of the complex with RCHCl₂. The reaction of the mixed ligand complexes with acetylacetone, monobenzoylacetone, and oxine led to the replacement of the coordinate (sal). The coordinated (sal) in the stable (CHCl₂CO₂)Cu(sal) could be condensed with the amino group of 2-aminophenol or 8-aminoquinoline (1 : 1 molar ratio) to produce the mixed five coordinate (CHCl₂CO₂)Cu(Schiff-base) complexes. The structures of these metal complexes are tentatively suggested on the bases of analytical, spectral, and magnetic data.     

Synthesis of ditopic ligands for the selective extraction of copper(II) nitrate and crystal structures of their Cu(II) complexes

We have synthesized two ditopic ligands for selective extraction of copper(II) nitrate. We also synthesized one cation-only binding analog for comparison. All three ligands were characterized by conventional techniques. Competitive two-phase metal ion solvent extraction experiments were performed at 25 °C over a period of 24 h. These ligands showed significant selectivity for Cu(II) ions, having the ditopic ligands extract 81 and 73% of the Cu(II) ions in a solution of different metal ions {Ni(II), Co(II), Cu(II), Zn(II), Cd(II), Pb(II)} at pH 5.09. Competitive transport experiments (water/chloroform/water) were undertaken employing each ligand separately as the ionophore in the membrane (chloroform) phase. No metal ion transport was observed, but a large concentration of Cu(II) was present in the membrane phase. Competitive anion extraction and transport were carried out with the ditopic ligands, yielding selective extraction and transport of nitrate. Furthermore, a pH isotherm of the best ditopic ligand (H₂L²) with Cu(II) was determined from pH 1.0 to 6.0, producing a pH_½ value of approximately 2.6. Finally, crystal structures of the ditopic ligands complexed with Cu(II) were determined and refined. The coordination geometry around the metal centers are distorted square planar and the Cu(II)-donor bond lengths fall within the normal range.     

Crystal structures of Cu(II) complexes of pyridine-2,6-dithiocarbomethylamide

The crystal structures of three copper(II) complexes of pyridine-2,6-dithiocarbomethylamide (P DT A) were determined by X-ray crystallographic methods. The structure of the bromide CuP DT ABr₂ · H₂O (2) is isomorphous to the known crystal structure of the chloride CuP DT ACl₂ · H₂O (1). The iodide CuP DT AI₂ ·D M F (3) is non-isomorphous to the other two halogenides, but shows a very similar square-pyramidal 5-coordination of the copper atom. In contrast to the halogenides, the crystal structure of the nitrate CuP DT A (H₂O)₂ · (NO₃)₂ (4) shows a square planar metal coordination by theP DT A ligand and one water molecule. If one includes the second water molecule and one oxygen atom of a nitrate ion, the metal coordination becomes distorted octahedral.