Heterometallic metallacyclophanes constructed from side-off bicompartmental ligands

Abstract

Two metallacyclophanes have been assembled by self-assembly processes involving the trianionic compartmental ligand (L^3-), nickel(II) and sodium or potassium ions: [LNiNa]₂·C₂H₅OH·2H₂O (1) and [LNiK]₂·C₂H₅OH·2H₂O (2) (the Schiff-base proligand, H₃L, is obtained by condensation of o-vanillin and DL-2,3-diaminopropionic acid). The structures of 1 and 2 can be viewed as resulting from two enantiomeric fragments, {LNiNa/K} connected to each other by the two carboxylato groups. The intramolecular distance between the phenyl rings is 3.64 Å. The sodium/potassium ions are coordinated by five oxygens in a planar pentagon. Weak intermolecular sodium/potassium···CH interactions are observed in the packing diagrams of the two compounds. The intra- and intermolecular non-covalent interactions are analyzed through several methods based on electron density, Bader’s QTAIM, non-covalent interactions index and natural bond orbitals. They confirm the in-plane five coordination of the alkali ion, which is of an electrostatic, non-covalent nature and the intermolecular interaction with σ C-H orbitals as well. The diffuse reflectance spectra of the two compounds show characteristic features of square-planar nickel(II) chromophores.

Graphical Abstract

Keywords:

• Heterometallic complexes
• metallosupramolecular chemistry
• Schiff-base ligands

Acknowledgements

The use of the HPC infrastructure at the Institute of Physical Chemistry of the Romanian Academy for performing the quantum chemical calculations is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Financial support from UEFISCDI (Grant PN-III-P4-ID-PCCF-2016-0088) is gratefully acknowledged.