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SM ISO690:2012 OGURŢOV, Ivan; TIHONOVSKY, Andrei. Ab initio study of the exchange interactions in binuclear V3+ complex [V2O(Bipy)4Cl2]2+. In: Physical Methods in Coordination and Supramolecular Chemistry. XVII, 27 septembrie  1 octombrie 2006, Chişinău. Chisinau, Republic of Moldova: 2006, p. 161. ISBN 9789975620666. 
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Physical Methods in Coordination and Supramolecular Chemistry XVII, 2006 

Conferința "The XVth International Conference Physical Methods in Coordination and Supramolecular Chemistry : The XVIIth Reading in memory of Acad. A.Ablov" Chişinău, Moldova, 27 septembrie  1 octombrie 2006  


Pag. 161161  


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The binuclear as well as other polynuclear transition metal complexes are of great interest due to the wide variety of their magnetic properties. The magnetic behavior of these complexes could change from diamagnetic to paramagnetic in dependence on the metal nature, the bridging ligand(s), the bridging geometry and the temperature, manifesting the antiferromagnetic or ferromagnetic interactions between localized metal spins, respectively. However, the nature of magnetic interaction is usually not known and the interpretations of the magnetic properties are based on the formal application of the Heisenberg approach. This work is devoted to the ab initio study of the exchange interactions in the [V2O(bipy)4Cl2]2+ (bipy = 1,1’bipyridine) complex of V(III). The geometry of this molecular system has been optimized in the C2 symmetry using ab initio gradient method realized in PC GAMESS version of the GAMESS (US) QC package. In all calculations the STO 6G atomic orbital basis set has been used. Geometric optimization was performed using ROHF gradient methods in the states with the total spin values S= 0, 1, 2 and also using the UHF gradient method in the spin state with S=2. The geometry data obtained theoretically are in a good accordance with the experimental Xray data. In the equilibrium geometry the ROHF+CI calculations were performed assuming 200 frozen core molecular orbitals (MO) and 9 active MO’s occupied by 14 electrons. In this approximation of the CI calculations the 1296 electron configurations with Sz = 0 are taken into consideration. The calculated ground state of this complex is the state with the total spin S = 2. In the first and second excited states the values of the total spin S are 1 and 0, respectively. These results are in an accordance with the experimental magnetic data interpreted in the suggestion of the ferromagnetic interaction between two spins S=1 localized on the V3+ ions. The gaps between the energy values of the ground and two excited states satisfy the Lande rule. This confirms the applicability of the Heisenberg approach used in the interpretation of the exchange interactions in the [V2O(bipy)4Cl2]2+ system. 

