21882-07-5Relevant articles and documents
Electrochemical Synthesis and Characterization of Copper(II) and Zinc(II) Coordination Compounds with Nicotinic and Picolinic Acids
Andriychenko, E. O.,Bespalov, A. V.,Bovyka, V. E.,Bukov, N. N.,Zelenov, V. I.
, p. 1697 - 1705 (2021/11/01)
Abstract: New methods for the electrochemical synthesis of copper(II) and zinc(II) coordination compounds with pyridinecarboxylic acids (nicotinic and picolinic) have been developed. The resulting compounds were characterized by quantitative analysis and IR spectroscopy. The vibrational frequencies of the synthesized compounds were calculated by a DFT quantum-chemical method, and the experimental IR spectra were interpreted on this basis. It was found that pyridinecarboxylate ions in all cases are coordinated both at the nitrogen atom and at the carboxylate group, however, in the case of nicotinic acid, this leads to the formation of coordination polymers, whereas for picolinic acid, the formation of mononuclear complexes is typical.
Access to a CuII-O-CuII motif: Spectroscopic properties, solution structure, and reactivity
Haack, Peter,Kaergel, Anne,Greco, Claudio,Dokic, Jadranka,Braun, Beatrice,Pfaff, Florian F.,Mebs, Stefan,Ray, Kallol,Limberg, Christian
supporting information, p. 16148 - 16160 (2013/11/19)
We report a complex with a rare CuII-O-CuII structural motif that is stable at room temperature, which allows its in-depth characterization by a variety of spectroscopic methods. Interest in such compounds is fueled by the recent discovery that a CuII-O-Cu II species on the surface of Cu-ZSM-5 is capable of oxidizing methane to methanol, and this in turn ties into mechanistic discussions on the methane oxidation at the dicopper site within the particulate methane monooxygenase. For the synthesis of our Cu2O complex we have developed a novel, neutral ligand system, FurNeu, exhibiting two N-(N′,N′-dimethylaminoethyl) (2-pyridylmethyl)amino binding pockets connected by a dibenzofuran spacer. The reaction of FurNeu with CuCl yielded [FurNeu](Cu2(μ-Cl))(CuCl 2), 1, demonstrating the geometric potential of the ligand to stabilize Cu-X-Cu moieties. A CuI precursor with weakly coordinating anions was chosen in the next step, namely [Cu(NCCH3) 4]OTf, which led to the formation of [FurNeu](Cu(NCCH 3))2(OTf)2, 3. Treatment of 3 with O 2 or PhIO led to identical green solutions, whose UV-vis spectra were markedly different from the one displayed by [FurNeu](Cu)2(OTf) 4, 4, prepared independently from FurNeu and Cu(OTf)2. Further investigations including PhIO consumption experiments, NMR and UV-vis spectroscopy, HR-ESI mass spectrometry, and protonation studies led to the identification of the green product as [FurNeu](Cu2(μ-O))(OTf) 2, 5. DOSY NMR spectroscopy confirmed its monomeric character. Over longer periods of time 5 decomposes to give [Cu(picoloyl)2], formed through an oxidative N-dealkylation reaction followed by further oxidation of the ligand. Due to its slow decomposition reaction, all attempts to crystallize 5 failed. However, its structure in solution could be determined by EXAFS analysis in combination with DFT calculations, which revealed a Cu-O-Cu angle that amounts to 105.17. Moreover, TDDFT calculations helped to rationalize the UV-vis absorptions of 5. The reactivity of complex 5 with 2,4-di-tert- butylphenol, DTBP, was also investigated; the initially formed biphenol product, TBBP, was found to further react in the presence of excessive O2 to yield 2,4,7,9-tetra-tert-butyloxepino[2,3-b]benzofuran, TBOBF, via an intermediate diphenoquinone. It turned out that 5, or its precursor 3, can even be employed as a catalyst for the oxidation of DTBP to TBBP or for the oxidation of TBBP to TBOBF.
One-dimensional copper(II) compound with a double out-of-plane carboxylato-bridge - Another polymorphic form of Cu(pyridine-2-carboxylate)2
Zurowska, Bogumi?a,Mroziński, Jerzy,Ciunik, Zbigniew
, p. 1251 - 1258 (2008/10/09)
The crystal and molecular structure of a blue-violet copper(II) compound of the formula Cu(2-pic)2 (2-pic = 2-picolinate or pyridine-2-carboxylate ion) was determined. Its structure consists of a copper atom lying in the centre of symmetry, trans square-planar coordinated via two pyridine nitrogens and the carboxylate oxygen atoms of the two picolinate anions. The bonding interaction between the copper and the oxygen of carboxylate atoms of neighboring planes completes the square-planar coordination to a strongly tetragonally distorted octahedral stereochemistry (CuN2 O2 O2′ chromophore), when long axial Cu-O bond distances are included. This intermolecular interaction, with the Cu?Cu distance of 5.163 ?, is weak, but permits to define the structure as a one-dimensional chain with a double out-of-plane carboxylate bridge. The magnetic behavior of the compound can be explained as a result of magnetic exchange within the chain through long Cu-O axial bonds (J = -0.73 cm-1) and a superexchange pathway through the hydrogen bond network between adjacent molecules (zJ′ = -0.06 cm-1). The magnitude and the nature of the exchange coupling are explained on the basis of the structural data results.
