Chiral Ni(Ⅱ)-Based coordination polymers with helixes and dinuclear clusters constructed from lactate synthons

Abstract

Chiral coordination polymers [Ni((R)-ceba) (1,3-dpp) (H2O)0.5] (HU15-R), [Ni((R)-ceba) (1,3-dpp) (H2O)0.5] (HU15–S), [Ni((R)-ceba) (4,4′-dib) (H2O)0.5] (HU16-R) and [Ni((S)-ceba) (4,4′-dib) (H2O)0.5](HU16–S) were prepared from lactate-derived synthons and different N-donor linkers under hydrothermal conditions (H2ceba = 4-(1-carboxyethoxy)benzoic acid, 1,3-dpp = 1,3-di(pyridine-4-yl)propane, 4,4′-dib = 4,4′-di (1H-imidazole-1-yl)-1,1′-biphenyl). Structural analysis confirmed that that all complexes are three-dimensional frameworks containing dinuclear [Ni2(CO2)2(H2O)]2+ clusters. In addition, four types of helical structures were also obtained though chiral transfer and asymmetric induction from chiral synthons among them. (R)-ceba2- anions and Ni(Ⅱ) ions were bridged together to construct right-handed (R)-ceba-Ni chains in HU15-R and HU16-R, while (S)-ceba2- anions were linked by Ni(Ⅱ) ions to build right-handed (S)-ceba-Ni chains in HU15–S and HU16–S. Apart from chiral synthons, achiral linkers 1,3-dpp and 4,4′-dib assembled with Ni(Ⅱ) ions to form single 1,3-dpp-Ni chains in HU15-R and HU15–S and double 4,4′-dib-Ni chains in HU16-R and HU16–S, respectively. Meanwhile, the introductions of N-donor ligands resulted in varied topological structures. HU15-R and HU15–S are 4-connected dia nets, while HU16-R and HU16–S are 8-connected frameworks. Moreover, magnetic experiments indicated that antiferromagnetic interactions exist in these complexes.