A series of coordination compounds containing rigid multi-pyridine based ligands: syntheses, structures and properties

Abstract

A series of coordination compounds Htpim (1), {[Zn(Htpim)₂(H₂O)₂]·(NO₃)₂·7.5H₂O}_n (2), {[Zn(Htpim)₂(H₂O)₂]·(CH₃COO)₂·5H₂O}_n (3), {[Cd(Htpim)₂(NO₃)₂]·9H₂O}_n (4), {[Cd(Htpim)₂(CH₃COO)(H₂O)]·(CH₃COO)·3H₂O}_n (5) were assembled from different metal(II) ions (Zn^II for compounds 2 and 3, and Cd^II for compounds 4 and 5) and a building block of 2,4,5-tri(4-pyridyl)-imidazole (Htpim). All the compounds were fully characterized by single crystal X-ray diffraction analysis. Compounds 2, 3, 4 and 5 possess a 1D chain structure. The compounds herein exhibit interesting piezochromic properties. Their emission colors are blue-shifted by grinding. On the basis of the PXRD patterns, the piezochromic behavior is due to a conversion from the crystalline to the amorphous state by changes in the molecular arrangement and in the intermolecular π–π interactions. Moreover, compound 1 exhibits positive solvatochromism, and could behave as a luminescent sensor for the detection of the Cu²⁺ ion.