Dimeric versus polymeric coordination in copper(ii) cationic complexes with bis(chelating) oxime and amide ligands

Abstract

A series of copper(ii) complexes with earlier reported ligands N,N'-bis(2-hydroxyiminopropionyl)-1,2-diaminoethane (H(2)pen) and 1,3-diaminopropane (H(2)pap) and novel open chain oxime and amide ligands, N,N'-bis(2-hydroxyiminopropionyl)-1,5-diaminopentane (H(2)papt), 1,6-diaminohexane (H(2)pah) and 1,7-diaminoheptane (H(2)pahp), were prepared and characterized by a variety of spectroscopic methods and X-ray structure analysis. Although a pH-potentiometric study revealed only monomeric species in solution, formation of both binuclear dimeric and 1D-polymeric topologies was found in solid state. In all complexes ligands provide bis-bidentate coordination to Cu(2+) ions via the nitrogen atoms of the oxime groups and the oxygen atoms of the amide groups to form CuN(2)O(2) planar fragments. Compound [Cu(Hpap)(ClO(4))(H(2)O)](x) was isolated in both dimeric (x = 2) and polymeric (x = n) state, representing an example of supramolecular isomerism. All the complexes are additionally stabilized by short intramolecular hydrogen bonds =N-O-H...O-N= between cis-arranged oximato-groups. Stabilization is more effective in the case of dimeric complexes compared to 1D-polymeric chain, which appears to be the reason of preferable dimerization versus polymerization in the studied set of compounds. The effect of polymethylene linker length on the conformation of the dimers is described.

Alkyl linker effects on the coordination topology of ditopic di(2-pyridylmethyl)amine carboxylate ligands with ZnIIand CuII: polymersvs.macrocycles

“…The longer alkyl chain length ligands are more entropically unfavourable for coordination interactions 7 and ligand solubility is limited in the polar solvents most compatible with metal salt precursors. 9 Accordingly, the attainment of X-ray diffraction-quality crystals of complexes from long alkyl ligands is a challenging problem; nevertheless we report success in this endeavour. Moreover, our X-ray crystal structure data of these complexes reveals topological variation beyond the 1D chains observed for C 3 COOH, C 4 COOH and C 5 COOH, in particular structures involving metallomacrocycles.…”

“…Zn II macrocycles (7)(8)(9). In contrast to the polymeric Zn II complexes of the short chain ligands (C n COOH, n ≤ 5), the structures with the longer analogues C 7 COOH, C 10 COOH and C 11 COOH are dominated by metallomacrocycles.…”

Cu(II), Ni(II) and Zn(II) mononuclear building blocks based on new polynucleating azomethine ligand: Synthesis and characterization

“…The C=N and N-O bond lengths are typical for the non-coordinated nondeprotonated oxime groups in the nitroso form. [22][23][24][25][26] In both ligand molecules of [Cu 2…”

“…Also EPR parameters strongly support the model based on monomeric and dimeric species ( Figure S6 Figure7). [22] To distinguish between the two geometries, geometric parameters τ (Equation 2) and R (Equation 3) were calculated:…”

Synthesis, crystal structures and tautomerism in novel oximes based on hydroxyalkylpyrazolones

“…3 Almost one fifth of the total world production of copper is obtained every year in solvent extraction processes that use phenolic oximes. 3 There are however, other areas of coordination chemistry where oximes are the subject of continuous research, such as molecular magnetism, [4][5][6] coordination polymers and molecular clusters 5,6 or biological modeling. [5][6][7][8] Probably the most straightforward way to obtain oximes is the condensation of a ketone or aldehyde with hydroxylamine.…”