Structural modulation of Co(II)-based helical coordination polymers with lactic derivatives via N-donor co-ligands

Chirality and helicity are closely related and important phenomena in nature. In this work, enantiomers (R)-H2cma and (S)-H2cma, obtained by coupling lactate with an aromatic carboxylic acid module, were employed as chiral ligands. Under hydrothermal conditions, using nitrogen-containing auxiliary ligands 1,4-di(1H-imidazol-1-yl)naphthalene (1,4-din) and 2,5-di(1H-imidazol-1-yl)pyridine (2,5-dip) as structure-directing agents, two pairs of chiral coordination polymers (CCPs) rich in helical chains were successfully prepared through self-assembly with Co2+: [Co((R)-cma)(1,4-din)(H2O)]·H2O (HU30-R), [Co((S)-cma)(1,4-din)(H2O)]·H2O (HU30-S), [Co((R)-cma)(2,5-dip)] (HU31-R) and [Co((S)-cma)(2,5-dip)] (HU31-R). All complexes crystallize in space group P212121 and exhibit enantiomeric helixes, where the central chirality of molecule is transferred into helical chirality of supramolecule. Moreover, structural differences from Co-ligands significantly influenced the final topology and dimensionality of complexes. Property characterization indicated that the complexes exhibit good thermal stability, semiconductor behavior and antiferromagnetic interactions.