Homochiral Zn(Ⅱ) coordination polymers with helixes constructed from semirigid lactate deriatives for circular polarization luminescence and fluorescent prober

Abstract

In the presence of nitrogen heterocyclic compound 2,5-di(1H-imidazole-1 -yl)pyridine (2,5-DIP), luminescent chiral synthons (R)-H₃CTA and (S)–H₃CTA assembled with Zn²⁺ ions to obtain enantiomers [Zn((R)-HCTA) (2,5-DIP)]_n (HU14-R) and [Zn((S)-HCTA) (2,5-DIP)]_n (HU14–S)) under hydrothermal condition, respectively. Partially deprotonated (R)-HCTA^2- anions were bridged by Zn²⁺ ions to form small left-handed (R)-HCTA-Zn chain in HU14-R, while (S)-HCTA^2- anions and Zn²⁺ ions were connected together resulting in enantiomeric right-handed chain in HU14–S. Moreover, larger left-handed (R)-HCTA-Zn-2,5-DIP chain and right-handed (S)-HCTA-Zn-2,5-DIP chain were found in HU14-R and HU14–S, respectively. These helical building blocks were joined together to create a pair of 3D frameworks with dia net, which show strong fluorescent characteristic and circular dichroism response. Further tests proved that HU14-R and HU14–S have circularly polarized light (CPL) activity and their luminescence anisotropy factors (g_1um) at 358 nm are +0.00346 and −0.00157, respectively. Moreover, as fluorescent probes, they have high stability, reliability and interference detection rate, and detection limits are up to 2.80 × 10⁻⁶ M for Cr₂O₇²⁻ and 6.19 × 10⁻⁶ M for MnO₄⁻.