Ab initio calculation of the magnetic exchange coupling in linear oxo-bridged heterobinuclear complexes of titanium (III), vanadium (III), and chromium (III)
✍ Scribed by Ch. Kolczewski; K. Fink; V. Staemmler
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 328 KB
- Volume
- 76
- Category
- Article
- ISSN
- 0020-7608
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✦ Synopsis
Quantum chemical ab initio calculations have been performed for the magnetic exchange coupling in three linear oxo-bridged heterobinuclear transition-metal Ž . Ž . complexes of the form L M III -O-M III L with M , M s Ti, V, Cr. In order to 5 1 2 5 1 2 simplify the calculations, the terminal ligands L are chosen as He-like model ligands with -donor properties. The metal cations in the complexes L TiOVL and L TiOCrL are 5 5 5 5
found to be ferromagnetically coupled at the complete active space self-consistent field Ž . Ž . CASSCF and valence configuration interaction CI levels, with exchange integrals J of q 13 and q12 cm y1 , respectively. Inclusion of correlation effects preserves the ferromagnetic coupling but enlarges the J values to q31 and q24 cm y1 . The L VOCrL 5 5 complex, on the other hand, is antiferromagnetic with J s y46 cm y1 at the valence CI level and y106 cm y1 after inclusion of electron correlation. A detailed analysis is performed in order to decompose J into a ''potential exchange'' and a ''superexchange'' contribution and to rationalize the different magnetic behavior of the three complexes.
The strong influence of electron correlation and relaxation effects on the numerical values of J is analyzed as well.