Structural Evidence for an Unusual Conformation and Weak Interligand Interactions in Two Copper Chelates with (o‐Nitrophenyl)ethylenediaminediacetic Acid

• Published in: European Journal of Inorganic Chemistry Vol. 2009; no. 11; pp. 1488 - 1494
• Main Authors: Allali, Mustapha, Jaud, Joël, Habbadi, Nouzha, Dartiguenave, Michèle, Beauchamp, André L., Benoist, Eric
• Format: Book Review Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag 01-04-2009
• Subjects: Aromaticity; Copper; N ligands; O ligands; Solid‐state structures; Stacking interactions
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200801201

Two mixed‐ligand copper(II) complexes, [Cu(L1)(H2O)]·H2O (1) and [Cu(L1)(bipy)]·2H2O (2), containing the title N‐substituted iminodiacetate (IDA) derivative (L12–) as primary ligand with and without 2,2′‐bipyridine as auxiliary ligand, have been synthesised. Both have been fully characterised by means of IR spectroscopy, mass spectrometry, elemental analysis and conductimetry, as well as X‐ray crystallography. The dominant structural feature of these complexes is the presence of a flexible coordinating arm on the IDA skeleton which controls the conformation of the resulting complexes. The CuII centre in complex 1 exhibits a distorted square‐pyramidal [4+1] coordination in which the apical site is unexpectedly occupied by the N(2) atom of the coordinating arm instead of a water molecule. The IDA skeleton adopts a tridentate mer‐O2N arrangement in 1, whereas in 2 it exhibits an unusual fac‐O2N(apical) configuration, which is observed for the first time for a tridentate IDA unit bearing a flexible arm containing a coordinating atom. The o‐nitro aromatic group in the flexible arm gives rise to different inter‐ and/or intramolecular stacking interactions. Classic intermolecular “nitrophenyl‐nitrophenyl” π‐π stacking interactions are observed between pairs of complex molecules in crystals of 1, whereas intramolecular “nitrophenyl‐pyridyl” interactions alternate with unprecedented interligand π‐π “nitrophenyl–metal chelate ring” interactions in crystals of 2.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Two mixed‐ligand copper(II) complexes bearing a flexible coordinating arm have been synthesised and fully characterised, and the impact of this arm on the structural features of these complexes has been evaluated. Both compounds display unusual inter‐ and/or intramolecular π‐π stacking interactions.