Synthesis, structures and properties of a series of novel left- and right-handed metal coordination double helicates with chiral channels

摘要

The reactions of LnCl_3 (Ln = lanthanide cations), L- or D-tartaric acid and molybdate in acidified aqueous solutions gave rise to the enantiopure left-or right-handed double helical coordination metal compounds, {A[Mo_2~(VI)O_2Ln~(III)(H_2O)_6(C_4H_2O_6)_2]·4H_2O}_n (Ln = Sm, Eu, Gd, Ho, Yb, Y; C_4H_2O_6 = L- or D-tartaric acid; A = NH_4 or H_3O; MoLn represent all complexes), which have been characterized by single X-ray crystal structure analyses, IR, FT-Raman, TGA, XRPD, electric conductivity, EPR and magnetic susceptibility studies. The TGA and XRPD studies for compound MoGd suggest that the backbone is "collapsed" with the removement of aqua ligands and crystallization water molecules. However, it is easily reverted to the original compound after being immersed in water, as confirmed by similar XRPD patterns. The electric conductivity studies for these compounds reveal they are semiconductors. As aforementioned, the conductivity behaviors for the dry sample and reversed sample of MoGd are also very similar, in line with the XPRD results. Study of the magnetic susceptibilities reveal that the magnetic behaviors for MoGd, MoDy, MoHo and MoYb obey the Curie-Weiss law.