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Electronic effects in 12-metallacrown-3 complexes. A theoretical and experimental study
Marie-Line Lehaire1, Axel Schulz, Rosario Scopelliti
1Institut de Chimie Moléculaire et Biologique, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
Inorganic Chemistry
|May 28, 2003
Summary
This study reveals metallamacrocycles exhibit greater negative charge on oxygen donors than organic crown ethers. Electron-withdrawing groups on metallacrowns significantly decrease guest binding affinity.
Area of Science:
- Supramolecular Chemistry
- Organometallic Chemistry
- Computational Chemistry
Background:
- Metallamacrocycles, specifically 12-metallacrown-3 complexes, are investigated for their electronic properties.
- Comparison with organic analogues, 12-crown-3, provides a baseline for understanding charge distribution.
Purpose of the Study:
- To determine Mulliken charges in a 12-metallacrown-3 complex using Hartree-Fock (HF) level calculations.
- To synthesize and evaluate the impact of electron-withdrawing chloro-substituents on metallacrown structure and host-guest properties.
Main Methods:
- Single-point analysis at the HF level for Mulliken charge determination.
- Mulliken population analysis for comparative study with organic crown ethers.
- Synthesis of a chloro-substituted 12-metallacrown-3 complex.
Main Results:
- The oxygen donor atoms in the 12-metallacrown-3 complex possess larger partial negative charges compared to the organic 12-crown-3.
- Chloro-substituents on the pyridonate ligand exert minimal influence on the metallacrown's structure.
- Binding affinity for lithium chloride (LiCl) and sodium chloride (NaCl) is reduced by approximately two orders of magnitude in the presence of chloro-substituents.
Conclusions:
- Metallamacrocycles demonstrate distinct electronic characteristics compared to their organic counterparts.
- Electron-withdrawing groups can be used to modulate the host-guest properties of metallacrown receptors, specifically reducing binding affinity.