title: Influence of steric and electronic properties of the defect site, lanthanide ionic radii, and solution conditions on the composition of lanthanide(III) alpha1-P2W17O6110- polyoxometalates.
abstract: This study identifies the principles that govern the formation and stability of Ln complexes of the (alpha(1)-P(2)W(17)O(61))(10-) isomer. The conditional stability constants for the stepwise formation equilibria, K(1cond) and K(2cond), determined by (31)P NMR spectroscopy, show that the high log K(1cond)/log K(2cond) ratio predicts the stabilization of the 1:1 Ln/ (alpha(1)-P(2)W(17)O(61))(10-) species. The value of log K(1cond) increases as the Ln series is traversed, consistent with the high charge/size requirement of the basic alpha(1) defect site. The conditional stability constants, K(2), are very low and are highly dependent on the countercations in the buffer. The source of the instability is understood from the crystal structures of the early-mid lanthanide analogues, where the close contact of the (alpha(1)-P(2)W(17)O(61))(10-) units result in severe steric encumbrance. The electronic properties of the alpha(1) defect along with the lanthanide ionic radii and countercation composition are important parameters that need to be considered for a rational synthesis of lanthanide polyoxometalates.
authors.affiliation: Department of Chemistry, Hunter College and the Graduate School of the City University of New York, New York, 10021, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhang
authors.forename: Robertha C
authors.initials: RC
authors.lastname: Howell
authors.forename: Qun-Hui
authors.initials: QH
authors.lastname: Luo
authors.forename: Heidi L
authors.initials: HL
authors.lastname: Fieselmann
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Todaro
authors.forename: Lynn C
authors.initials: LC
authors.lastname: Francesconi
mesh_terms: D018360:Crystallography, X-Ray; D028581:Lanthanoid Series Elements / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D010759:Phosphorus Isotopes; D017973:Tungsten Compounds / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D028581:Lanthanoid Series Elements; D010759:Phosphorus Isotopes; D017973:Tungsten Compounds