TRINUCLEAR FRAGMENTS AS NUCLEATION CENTERS - NEW POLYOXOALKOXYVANADATES BY (INDUCED) SELF-ASSEMBLY

The presence of pentaerythritol (C(CH2OH)(4)) in an aqueous vanadate s olution leads-depending on the pH value and other specific reaction co nditions-to the formation of (CN3H6)(4)Na-2 [(H4V6P4O30)-P-IV{(CH2)(3) -CCH2OH2]. 14H(2)O (1), Na-6[(H4V6P4O30)-P-IV{(CH2)(3)CCH2OH}(2)]. 18 H2O (2), (NH4)(7)[(H7V12V7O50)-V-IV-O-V (CH2)(3)CCH2OH]. 11.5 H2O . (3 ), (CN3H6)(4)[(V3V4O19F)-V-IV-O-V(CH2)(3)CCH2OH] . 5.25 H2O (4), Na-6[ (V10V2O30F2)-V-IV-O-V{(CH2)(3)CCH2OH}(2)]. 22- H2O (5) or N3H6)(4)[(V2 V8O28F2)-V-IV-O-V-{(CH2)(3)CCH2OH}(2)] . 4 H2O (6). The corresponding anions contain as basic structural elements trinuclear {V3O13} or {V3O 12F} units, which are stabilized by the organic substituent acting as a tripod ligand. It can be assumed in principle that these units act a s nucleation centres during the formation processes of the cluster ani ons. In this context it is remarkable that the trinuclear units can ev en occur in a quasi-isolated state, as in the anions of 1 and 4, The c ompounds were characterized by IR, UV/Vis/NIR and EPR spectroscopy as well as by magnetochemical investigations and single-crystal X-ray str ucture determinations. Susceptibility data are especially useful for i dentifying the trinuclear units as well as the nature of their magneti c coupling with the rest of the structure.