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

Abstract

The O-O-N-N-O-type pentadentate ligands H3ed3a, H 31,2-pd3a, H3eda2p and H3ed3p (H 3ed3a stands for ethylenediamine-N,N,N′-triacetic acid; H 31,2-pd3a stands for 1,2-propanediamine-N,N,N′-triacetic acid; H3eda2p stands for ethylenediamine-N-acetato-N,N′-di-3- propionic acid and H3ed3p stands for ethylenediamine-N,N,N′- tri-3-propionic acid) and the corresponding novel octahedral nickel(II) complexes have been prepared and characterized. H3ed3a, H 31,2-pd3a, H3eda2p and H3ed3p 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)]2·2H2O 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⋯OH2 unit. © 2012 Elsevier Ltd. All rights reserved.