Chiral Ca–Mn-frameworks with double helical chains and one-dimensional channels constructed from enantiomorphous lactate synthons

Abstract

Under solvothermal synthetic condition, lactate derivatives (R)-5-(1- carboxyethoxy)isophthalic acid ((R)-H₃CIA) and (S)-5-(1-carboxyethoxy)isophthalic acid ((S)–H₃CIA) assembled with Ca(Ⅱ) and Mn(Ⅱ) ions to obtain enantiomers {[MnCa_0.5((R)-CIA)(H₂O)]·((CH₃)₂NH₂CH₃CO₂)_0.5(H₂O)}_n (HU21-R) and {[MnCa_0.5((S)-CIA)(H₂O)]·((CH₃)₂NH₂CH₃CO₂)_0.5(H₂O)}_n (HU21–S), respectively. Complexes HU21-R and HU21–S belong to orthorhombic crystal system with chiral space group I2₁2₁2₁. Single crystal X-ray diffraction analysis revealed that all oxygen atoms of synthons (R)-CIA^3- and (S)-CIA^3- participated in the coordination with metal ions. Thus, semi-rigid (R)-CIA^3- and (S)-CIA^3- anions become rigid linkers in HU21-R and HU21–S. Fragments of (R)-CIA^3- anion are connected by Ca(Ⅱ) ions to build right-handed double helical chains in HU21-R, while the enantiomeric left-handed double helixes are constructed by (S)-CIA^3- fragments and Ca(Ⅱ) ions in HU21–S. Additionally, Mn(Ⅱ) centers and CIA³⁻ anions resulted in a rare 4,4,4-connected net with point symbol of (4².6².8²)₃(4².6⁴). Ca(Ⅱ) ions were further filed into Mn-CIA-framework to form a three dimensional structure with one dimensional channel. Moreover, magnetic test indicates that the framework has a canted antiferromagnetic behavior.