Localization and Delocalization of Spin Density in Mixed‐Valence (V IV /V V ) [(V 2 O 3 ) 2 (PhPO 3 ) 4 ⊂F] – n ( n = 1, 2): Theoretical and Experimental Studies

Based on XRD and optimized structures of the cage compound [(V 2 O 3 ) 2 (PhPO 3 ) 4 ⊂F] – n in singlet ( n = 1) and doublet ( n = 2) states DFT calculations were carried out to determine the energies and spin density distribution for the symmetries D 2 d , C 2 v , and C s . It turned out, that the cage with C s symmetry not only represents the energetically more stable doublet system (with respect to D 2 d and C 2 v ‐symmetries) but also corresponds to the real compound under study. The SOMO of the S = 1/2 cage represents an antibonding state and the volume of the cage in this state is larger than that in the S = 0 state. The calculated ESR hyperfine coupling constants are in acceptable agreement with those determined by ESR. Experimentally the localization/delocalization of spin density was determined via ESR as a function of temperature and adsorption of the cage on Al 2 O 3 , respectively. A proposal is given for the localization/delocalization of spin density based on thermally driven changes of the cage symmetry in combination with the hopping of the unpaired electron inside the cage.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)