Synthetic, Crystallographic, and Computational Study of Copper(II) Complexes of Ethylenediaminetetracarboxylate Ligands

Copper(II) complexes of hexadentate ethylenediaminetetracarboxylic acid type ligands H4eda3p and H4eddadp (H4eda3p = ethylenediamine-N-acetic-N,N′,N′-tri-3-propionic acid; H4eddadp = ethylenediamine-N,N′-diacetic-N,N′-di-3-propionic acid) have been prepared. An octahedral trans(O6) geometry (two propionate ligands coordinated in axial positions) has been established crystallographically for the Ba[Cu(eda3p)]·8H2O compound, while Ba[Cu(eddadp)]·8H2O is proposed to adopt a trans(O5) geometry (two axial acetates) on the basis of density functional theory calculations and comparisons of IR and UV−vis spectral data. Experimental and computed structural data correlating similar copper(II) chelate complexes have been used to better understand the isomerism and departure from regular octahedral geometry within the series. The in-plane O−Cu−N chelate angles show the smallest deviation from the ideal octahedral value of 90°, and hence the lowest strain, for the eddadp complex with two equatorial β-propionate rings. A linear dependence between tetragonality and the number of five-membered rings has been established. A natural bonding orbital analysis of the series of complexes is also presented.

Chelating properties of EDTA-type ligands containing six-membered backbone ring toward copper ion:Structure, EPR and TD-DFT evaluation

The P-APC ligands (EDTA-like aminopolycarboxylate ligands comprising 1,3-propanediamine backbone) H(4)pdta, H(4)pd(3)ap, H(4)pddadp and H(4)pdtp (H(4)pdta = 1,3-propanediamine-N,N,N',N'-tetraacetatic acid; H(4)pd(3)ap = 1,3-propanediamine-N,N,N'-triacetic-N'-3-propionic acid; H4pddadp = 1,3-propanediamine-N,N'-diacetatic-N,N'-di-3-propionic acid; H(4)pdtp = 1,3-propanediaminetetra-3-propionic acid) were investigated. The chelating ligands coordinate to copper(II) via five or six donor atoms affording distorted trigonal-bipyramid and octahedral structures that were verified by X-ray analysis for Ba[Cu(pd(3)ap)]center dot 6H(2)O (1) and trans(O-6)-Ba[Cu(pddadp)]center dot 8H(2)O (2) complexes respectively. The impact of counter-ions on the P-APC complexes is shown in detail together with the analysis of another strain parameters. EPR spectral results confirm the penta-coordination of 1 and hexa-coordination of 2 in aqueous solution, even if several Cu(II) species with different protonation degree exist as a function of pH, and indicate that a hexa-coordinated structure is favored when the two axial COO- donors close five-membered chelate rings. We also present here the results of molecular mechanics (LFMM) calculations based on our previously-developed force field along with results of DFT (Density Functional Theory). On the basis of extensive DFT and TD-DFT calculations the B1LYP/6-311++G(d,p) level has been seen as an accurate theory for calculating and predicting the UVVis spectra in case of copperP-APC compounds. (C) 2016 Elsevier Ltd. All rights reserved

Crystal structure, configurational and DFT-NEDA analysis of nickel(II) complexes with pentadentate ed3a-type ligands

<p>The O-O-N-N-O-type pentadentate ligands H(3)ed3a, H(3)1,2-pd3a, H(3)eda2p and H(3)ed3p (H(3)ed3a stands for ethylenediamine-N,N,N'-triacetic acid; H(3)1,2-pd3a stands for 1,2-propanediamine-N,N,N'-triacetic acid; H(3)eda2p stands for ethylenediamine-N-acetato-N,N'-di-3-propionic acid and H(3)ed3p stands for ethylenediamine-N,N,N'-tri-3-propionic acid) and the corresponding novel octahedral nickel(II) complexes have been prepared and characterized. H(3)ed3a, H(3)1,2-pd3a, H(3)eda2p and H(3)ed3p ligands coordinate to nickel(II) ion via five donor atoms (three deprotonated carboxylate atoms and two amine nitrogens) affording octahedral geometry in case of all investigated Ni(II) complexes. A sixth place within octahedra has been occupied by the molecule of water. A six coordinate, octahedral geometry has been established crystallographicaly for the [Ni(H2O)(6)][Ni(ed3a)(H2O)](2)center dot 2H(2)O complex. Structural data correlating similar chelate Ni(II) complexes have been used to carry out an extensive configuration analysis. This is discussed in relation to information obtained for similar complexes. The infra-red and electronic absorption spectra of the complexes are discussed in comparison with related complexes of known geometries. Molecular mechanics and density functional theory (DFT) have been used to model the most stable geometric isomer yielding, at the same time, significant structural data. The results from density functional studies have been compared with X-ray data. Natural Energetic Decomposition Analysis (NEDA) has been done for the LNi center dot center dot center dot OH2 unit. (C) 2012 Elsevier Ltd. All rights reserved.</p>