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(Alpha-diimine)chromium complexes: molecular and electronic structures; a combined experimental and density
Meenakshi Ghosh1, Stephen Sproules, Thomas Weyhermüller
1Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
Inorganic Chemistry
|May 31, 2008
Summary
This study synthesizes novel chromium complexes, [Cr(1L)2] and [Cr(III)(2L*)(acac)2], revealing their unique electronic structures and magnetic properties. These findings advance the understanding of chromium-based radical systems and their potential applications.
Area of Science:
- Inorganic Chemistry
- Organometallic Chemistry
- Materials Science
Background:
- Chromium complexes with diiminato ligands are of interest due to their diverse electronic and magnetic properties.
- Understanding the electronic structure of these complexes is crucial for designing new materials with tailored functionalities.
Purpose of the Study:
- To synthesize and characterize novel chromium complexes with alpha-diiminato ligands.
- To investigate the electronic structure and magnetic properties of these newly synthesized chromium complexes.
- To explore the impact of ligand modifications on the properties of chromium complexes.
Main Methods:
- Synthesis of chromium complexes via reactions involving chromium(III) precursors and diiminato ligands in tetrahydrofuran.
- Characterization using X-ray crystallography to determine molecular structures.
- Magnetic susceptibility measurements to determine ground state spin (S).
- Density Functional Theory (DFT) calculations, including broken symmetry (BS) DFT, to confirm electronic structures.
Main Results:
- Synthesis of [Cr(1L)2] (S=1), featuring a high-spin Cr(II) ion coupled antiferromagnetically with two anionic alpha-diiminato(1-) ligand pi radicals.
- Structural analysis of [Cr(1L)2] revealed a distorted tetrahedral, nearly square-planar geometry with a C-N imine bond length indicative of a pi radical anion.
- Synthesis of [Cr(III)(2L*)(acac)2] (S=1) and its oxidized form [Cr(III)(2L(ox))(acac)2](PF6) (S=3/2), with octahedral geometries.
- DFT calculations confirmed the electronic structures of the synthesized complexes, describing [Cr(1L)2] as [Cr(II)(1L*)2].
Conclusions:
- The electronic structure of [Cr(1L)2] is best described as a Cr(II) center with two ligand pi radicals, [Cr(II)(1L*)2].
- The study demonstrates the formation of chromium(II) radical complexes and chromium(III) complexes with distinct electronic configurations.
- Ligand structure and oxidation state significantly influence the properties of these chromium complexes, offering pathways for tuning their magnetic behavior.
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