Multifunctional chiral metal hydrogen-bonded organic frameworks constructed from lanthanide ions with a trigonal prismatic coordination environment

Abstract

Two pairs of chiral enantiomers D/L-Dy(PMP)₃·2H₂O (D-1/L-1) and D/L-Yb(PMP)₃·2H₂O (D-2/L-2) were synthesized by the introduction of enantiomerically pure D/L-PMP (PMP = (phosphonomethyl)proline) ligands into lanthanide coordination chemistry. The chiral characteristics of these products were confirmed by single crystal X-ray diffraction, second harmonic generation (SHG) measurements and circular dichroism (CD) spectroscopy. These complexes are composed of 1D chains constructed from lanthanide ions with a trigonal prismatic coordination geometry and PMP ligands. The assembly of the 1D chains led to the formation of a lanthanide hydrogen-bonded organic framework with 1D water chains filled in the channels. Zero-field slow relaxation of magnetization was detected in L-1, whereas L-2 showed field-induced single-molecule magnet (SMM) behavior. Complexes D-1, L-1 and L-2 show proton conductive ability and their conductivity values reach the order of 10⁻⁵ S cm⁻¹ at 90 °C and 98% relative humidity.