Construction of four 3d-4f heterometallic pillar-layered frameworks containing left-and right-handed helical chains and a I- chemosensor

Four new heterometallic coordination complexes, namely, {[Zn(4)Ln(2)(imdc)(4)(SO4)(H2O)(8)]center dot 4H(2)O}(n) [Ln = Nd (1), Sm (2), Eu (3), Gd (4); H(3)imdc = imidazole-4,5-dicarboxylic acid], were hydrothermally synthesized by the reactions of Ln(2)O(3) with imidazole-4,5-dicarboxylic acid and ZnSO4 center dot 7H(2)O and characterized by single-crystal X-ray diffraction, infrared spectroscopy (IR), elemental analysis (EA), thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). The single-crystal X-ray diffraction analyses reveal that these polymers are isostructural and possess an interesting 3D pillar-layered architecture with 4(24)center dot 6(4) topology, in which 2D layers constructed by alternately arranged 1D right-/left-handed helical chains of [Zn-2(mu(5)-imdc)](n) bridged via dimeric Eu-2 units are pillared by mu(2)-SO42- and mu(3)-imdc(3-) anions. The liquid fluorescence of compounds 1-3 at room temperature shows that these complexes are very good chemosensors for I- ion, and the response of the sensor is based on fluorescence quenching of Zn-Ln MOFs by iodine ions.