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A New Class of Ferromagnetically-Coupled Mixed Valence Vanadium(IV/V) Polyoxometalates
- Source :
- Chemistry-A European Journal, Chem.Eur.J.
- Publication Year :
- 2003
- Publisher :
- Wiley, 2003.
-
Abstract
- Reaction of [V(VI)OCl(2)(thf)(2)] with a bidentate nitrogen-donor ligand (L: phen=1,10-phenanthroline, 5-mephen=5-methyl-1,10-phenanthroline, bipy=2,2'-bipyridine, 5,5'-me(2)bipy=5,5'-dimethyl-2,2'-bipy) in methyl alcohol, in the presence of triethylamine, leads to the formation of hexameric [V(2) (IV)V(4) (V)] oxo-alkoxo-vanadates of the general formula [V(6)O(12)(mu(2)-OCH(3))(4)(L)(4)].x H(2)O [L=phen (1.4 H(2)O), 5-mephen (2.6 H(2)O), bipy (3.4 H(2)O), 5,5'-me(2)bipy (4.H(2)O)]. X-ray structure analysis of 1.2 H(2)O and 4.8 CH(3)OH revealed a pair of V(3)O(13)N(4) trimeric units sharing two corners, with a centrosymmetric planar V(6)-core. In addition, a fully oxidized V(V) species [V(V) (4)O(8)(OCH(3))(2)(mu(3)-OCH(3))(2)(5,5'-me(2)bipy)(2)].3 CH(3)OH (5.3 CH(3)OH) was isolated from the reaction mixture used for the synthesis of 4.H(2)O. The crystal structure of 5.3 CH(3)OH revealed a dicubane-like framework with two missing vertices. Electron paramagnetic resonance (EPR) and variable temperature magnetic susceptibility studies for the hexamers 1.4 H(2)O and 3.4 H(2)O showed the complete localization of the single 3d electrons on the V(IV) ions and unusual ferromagnetic interaction between the two paramagnetic vanadium(IV) ions separated by a distance of about 5.1 A. Furthermore, intermolecular antiferromagnetic interactions through pi-contacts of phenyl rings were observed for these species below 8 K. The ferromagnetic exchange coupling observed in the hexanuclear compounds 1.4 H(2)O and 3.4 H(2)O is also discussed using ab initio UHF calculations on a model compound. The value of the exchange coupling constant (3.7 cm(-1)) for this model compound, calculated using the broken symmetry approach, is in good agreement, both in sign and magnitude, with the experimental J values (6.00 cm(-1) for 1.4 H(2)O and 8.54 cm(-1) for 3.4 H(2)O).
- Subjects :
- chemical reaction
2,2' bipyridine
Denticity
Ab initio
Crystal structure
X ray analysis
ligand
Catalysis
law.invention
Magnetic susceptibility
Paramagnetism
phenanthroline derivative
Computational chemistry
law
Intermolecular interaction
Antiferromagnetism
Electron paramagnetic resonance
Reaction kinetics
Paramagnetic resonance
methanol
ab initio calculation
Valence (chemistry)
Chemistry
Polyoxometalates
electron spin resonance
Organic Chemistry
article
ferromagnetic material
temperature
Vanadium
General Chemistry
vanadium derivative
1,10 phenanthroline
2,2' bipyridine derivative
structure analysis
triethylamine
Vanadium compounds
Crystallography
UHF calculations
Synthesis (chemical)
magnetism
metal derivative
molecular interaction
Coupling constants
Ferromagnetism
Ferromagnetic materials
Subjects
Details
- ISSN :
- 15213765 and 09476539
- Volume :
- 9
- Database :
- OpenAIRE
- Journal :
- Chemistry - A European Journal
- Accession number :
- edsair.doi.dedup.....16ef48b5a9d646b631b66bebdd21b2ad