Organic acid effect on the structures of Cd(II) metal-organic complexes based on 2-(3-pyridyl)imidazo[4,5-<Emphasis Type="Italic">f</Emphasis>]-1,10-phenanthroline

Three new Cd(II) complexes consisting of phenanthroline derivative and organic acid ligands, formulated as Cd₃(3-PIP)₂(L¹)₆] (I), Cd(3-PIP)(L²)] · H₂O (II), and Cd(3-PIP)(L³)] (III) (3-PIP = 2-(3-pyridyl)imidazo4,5-f]-1,10-phenanthroline, HL¹ = 3,5-dinitrobenzoic acid, H₂L² = oxalic acid, H₂L³ = benzene-1,3-dicarboxylic acid), have been synthesized via the hydrothermal reaction and characterized by single-crystal X-ray diffraction, elemental analyses and FT-IR spectra. Complex I is a trinuclear structure. Complex II features a 1D zigzag chain. Complex III shows a twisted double chain of binuclear units sustained by double carboxylate bridges. Three complexes are further extended into 3D supramolecular frameworks by hydrogen bonding and π-π-stacking interactions. The structural differences among I–III show that the organic carboxylates have important effects on the structures. Furthermore, the supramolecular interactions are the critical factors in determining the final structures of the complexes. In addition, the thermal stabilities and luminescent properties of complexes I and II are also investigated.