Structural study of copper(II) sulfate solution in highly concentrated aqueous ammonia by x-ray absorption spectra

π–π Stacking Interaction in an Oxidized CuII–Salen Complex with a Side‐Chain Indole Ring: An Approach to the Function of the Tryptophan in the Active Site of Galactose Oxidase

“…The pre‐edge of [ 1 ]PF 6 was slightly shifted to the higher region than that of 1 , but the shift was rather small for the valence‐state change of the central copper(II) ion . In general, the edge and pre‐edge in K‐edge XANESs depend on the symmetry of the complexes; square‐planar Cu II complexes exhibit a shoulder in the edge, whereas square‐pyramidal complexes do not show a corresponding shoulder . The present observation of [ 1 ]PF 6 could be considered as being due to the perturbation by the close contact of the indole ring with the central copper ion.…”

“…[47,58] In general, the edge and pre-edge in K-edge XANESs depend on the symmetry of the complexes;s quare-planar Cu II complexes exhibit as houlder in the edge, whereas square-pyramidalc omplexes do not show ac orresponding shoulder. [59] The present observation of [1]PF 6 could be considered as being due to the perturbation by the closec ontact of the indole ring with the central copper ion. Actually,t he spectralc hange has also been observed in the case of the close contact of the counter anion to the Cu III ion in the square-planar geometry.…”

Cuii in Liquid Ammonia: An Approach by Hybrid Quantum‐Mechanical/Molecular‐Mechanical Molecular Dynamics Simulation

“…Solution X-ray diffraction yielded a CuÀN distance of 1.93 ä, which is certainly too short compared to various EXAFS measurements, and X-ray single-crystal data for similar structures supplied bond lengths in the range of 2.00 ± 2.05 ä. [10,11,14,15,46] DV-Xa calculations [9] have been utilized to claim that the octahedral and trigonal bipyramidal model could be discarded and Valli et al have thus concluded that the coordination number of Cu II ions in liquid ammonia should be five (with a square pyramidal structure in which the copper ion is lifted above the average nitrogen plane). The obtained [2 4] configuration from our QM/MM simulation leads to experimental results similar to those observed for the common [4 2] structure, most probably showing different intensities of the corresponding peaks in the spectra.…”

“…The structure of copper II complexes in ammonia has been studied by X-ray absorption fine structure (EXAFS) [9,10] and X-ray diffraction (XRD). [11] The EXAFS results concluded that the Cu II ion was coordinated by five ammonia ligands at equal distances. However, the use of a single scattering plane wave approximation in the data analysis has prevented to resolve a possible difference in ™equatorial∫ and ™axial∫ distances and thus, as stated by the authors, the EXAFS investigation is not suitable for supplying a proof of equal or unequal bond lengths.…”

Density functional study of Cu2+-phenylalanine complex under micro-solvation environment

“…However, the solid Cu 2+ complexes with aliphatic amines, pyridines [36] or ammonia [37][38][39] have been recognized to show a variety of different coordination: square planar (fourfold) [40,41], square pyramidal (fivefold) [42,43] and distorted square bipyramidal (sixfold) [44,45]. Rulisek and Vondrasek [46], who have exploited several metalloproteins and transition metal complexes from the Protein Data Bank (PDB) and the Cambridge Structure Database (CSD), ascertained that the Cu 2+ metal ion mostly prefer a square planar structure, although a few complexes also exhibit trigonal bipyramidal geometries.…”