H-shaped oxalate-bridging lanthanoid-incorporated arsenotungstates
Hanhan Chen1, Zikang Xiao1, Bing Yan1
1Henan Key Laboratory of Polyoxometalate Chemistry, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, P. R. China. mpt@henu.edu.cn jyniu@henu.edu.cn.
Abstract:
Three oxalate-bridging lanthanide-based polyoxometalates (Ln-POMs) K17Na2H5[{(As2W19O67(H2O))Ln(H2O)2}2(C2O4)]·50H2O. [Ln = Sm3+ (1), Pr3+ (2), and Ce3+ (3)] were successfully synthesized. The structures were further characterized by single-crystal X-ray diffraction analyses, Raman spectroscopy, elemental analyses, powder X-ray diffraction (PXRD), IR spectra, UV/vis diffuse reflectance spectroscopy, and thermogravimetric analysis (TGA). The structural characterization study reveals that Ln-POMs 1-3 crystallize in the form of the triclinic space group P1[combining macron] and consist of an oxalate bridging di-Ln3+-incorporated H-shaped dimer, which can also be viewed as a combination of two half-units {Ln(As2W19O67(H2O))(H2O)2}222- related by an inversion center. It is worth noting that the opening angle (33.01°) from the [As2W19O67(H2O)]14- fragment in 1-3 is less than that of the [As2W19O67(H2O)]14- precursor (40.99°). Furthermore, the stability of 1-3 in aqueous solution and their solid-state photoluminescence properties have also been investigated in this work.
Related Concept Videos
00:43Complexometric Titration: Ligands
02:42Valence Bond Theory
02:51Metal-Ligand Bonds
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
01:19Complexation Equilibria: The Chelate Effect