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Density functional theory study on the bridge structure in dimeric aluminum (III) water complexes
Qiang Miao1, Qing Cao, Shuping Bi
1State Key Laboratory of Coordination Chemistry, Department of Chemistry, Nanjing University, Nanjing 210093, People's Republic of China.
The Journal of Chemical Physics
|August 31, 2004
Summary
Density-functional theory reveals that electrostatic repulsion between hydroxyl groups influences polyaluminum structures. While aluminum-hexaaquo complexes dominate, hydroxyl ligands can stabilize five-coordinate configurations.
Area of Science:
- Computational Chemistry
- Inorganic Chemistry
- Materials Science
Background:
- Aluminum (III) ions are prevalent in aqueous solutions and biological systems.
- Understanding the structure of aluminum-water complexes is crucial for various chemical and environmental processes.
Purpose of the Study:
- To investigate the structural preferences of dimeric aluminum (III) water complexes.
- To explore the role of different bridging ligands (oxygen, water, hydroxyl) and their arrangements on complex stability.
Main Methods:
- Density-functional theory (DFT) calculations were employed.
- Various structural configurations, including cis/trans isomers, were analyzed.
Main Results:
- Electrostatic repulsion between hydroxyl ligands significantly impacts polyaluminum structure.
- Aluminum-hexaaquo complexes are the predominant species.
- Species with fewer charges or more hydroxyl ligands favor a five-coordinate trigonal bipyramidal configuration.
- Water as a bridge ligand is insufficient for stabilizing two Al(III) ions due to its neutral charge.
Conclusions:
- The stability and structure of aluminum-water complexes are sensitive to the nature and arrangement of bridging ligands.
- Hydroxyl-bridged aluminum complexes exhibit low energy barriers for interconversion, suggesting dynamic behavior at room temperature.