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1H and 17O NMR relaxometric and computational study on macrocyclic Mn(II) complexes
Gabriele A Rolla1, Carlos Platas-Iglesias, Mauro Botta
1Dipartimento di Scienze e Innovazione Tecnologica, Università del Piemonte Orientale Amedeo Avogadro, Viale T. Michel 11, 15121, Alessandria, Italy.
Inorganic Chemistry
|February 27, 2013
Summary
This study investigated manganese(II) complexes with cyclen-based ligands, revealing varying coordination numbers and water molecule interactions. The Mn(II)-DO1A complex exhibits the fastest water exchange rate ever recorded for a Mn(II) complex.
Area of Science:
- Inorganic Chemistry
- Coordination Chemistry
- Nuclear Magnetic Resonance Spectroscopy
Background:
- Manganese(II) complexes with cyclen-based ligands are crucial in various applications.
- Understanding their coordination environment and water dynamics is key to optimizing their function.
Purpose of the Study:
- To conduct a detailed relaxometric investigation of Mn(II) complexes with cyclen-based ligands.
- To elucidate the structural properties and water exchange dynamics of these complexes in solution.
- To compare the properties of different Mn(II) complexes with varying ligand denticity.
Main Methods:
- 1H and 17O relaxometry to study Mn(II) complexes.
- Density Functional Theory (DFT) calculations (B3LYP model) for structural and electronic property determination.
- Analysis of hyperfine coupling constants and NMR chemical shifts.
Main Results:
- Mn(II) complexes with DO3A and 1,7-DO2A ligands exhibit no inner sphere water molecules (q=0), indicating seven- and six-coordinate metal ions, respectively.
- The [Mn(1,4-DO2A)] complex predominantly exists as a species with one coordinated water molecule (q=1).
- The [Mn(DO1A)(H2O)]+ complex demonstrates the highest water exchange rate (k(ex)298 = 60 × 10^8 s^-1) reported for any Mn(II) complex.
Conclusions:
- Ligand structure significantly influences the coordination number and water molecule presence in Mn(II) complexes.
- The [Mn(DO1A)(H2O)]+ complex exhibits exceptionally fast water exchange, offering potential for novel applications.
- DFT calculations provide valuable insights into the structure-property relationships of these Mn(II) complexes.
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