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Updated: Jul 5, 2026
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Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry
Published on: June 8, 2022
Three overcrowded zinc(II) complexes with potentially hexadentate polypyridyl ligands
Alan Hazell1, Ole Mønsted, Jens Christian Rasmussen
1Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Arhus C, Denmark. ach@chem.au.dk
Summary
This study examines zinc complexes with varying pyridyl and quinolyl ligands. Increasing quinolyl groups systematically alters the zinc atom's coordination geometry, shifting it from octahedral towards pentagonal bipyramidal structures.
Area of Science:
- Coordination chemistry
- Inorganic chemistry
- Supramolecular chemistry
Background:
- Zinc complexes with polydentate nitrogen ligands are crucial in catalysis and materials science.
- Understanding the precise coordination geometry around metal centers is key to predicting their reactivity and properties.
- Ligand design offers a powerful tool to tune the electronic and steric environment of metal ions.
Purpose of the Study:
- To synthesize and characterize three novel zinc(II) complexes with N-donor ligands featuring varying numbers of pyridyl and quinolyl moieties.
- To investigate the impact of ligand structure, specifically the incorporation of quinolyl groups, on the coordination geometry of the central zinc(II) ion.
- To establish a structure-property relationship by analyzing systematic changes in geometry as ligand overlap increases.
Main Methods:
- Single-crystal X-ray diffraction was employed to determine the solid-state structures of the three zinc(II) complexes.
- Detailed crystallographic analysis was performed to describe the coordination environment around the zinc(II) center in each complex.
- Comparative analysis of the geometric parameters (bond lengths, angles, and deviations from ideal geometries) was conducted.
Main Results:
- Three zinc(II) complexes, [Zn(L1)](ClO4)2, [Zn(L2)](ClO4)2, and [Zn(L3)](ClO4)2, were successfully synthesized and characterized.
- The coordination geometry around the zinc(II) ion in complex (I) is intermediate between octahedral and pentagonal bipyramidal.
- Complexes (II) and (III), with increasing numbers of quinolyl groups, exhibit coordination geometries closer to pentagonal bipyramidal, with quinolyl groups occupying equatorial positions.
Conclusions:
- The number of quinolyl groups in the N-donor ligand systematically influences the coordination geometry of the zinc(II) center.
- An increase in quinolyl substituents leads to a greater deviation from ideal octahedral geometry towards a pentagonal bipyramidal arrangement.
- This study highlights the utility of ligand design in controlling the coordination sphere and potential reactivity of metal complexes.
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