Three interdigitated metal–quinolone complexes from self-assembly of mixed ligands and cadmium salts

Three interdigitated metal–quinolone complexes, [Cd2(cfH)2(btec)(H2O)2]·6H2O (1), [Cd2(ppaH)2(1,3-bdc)2]·4.25H2O (2) and [Cd2(LevofH)(1,3-bdc)2(H2O)2] (3) (cfH = ciprofloxacin, ppaH = pipemidic acid, LevofH = levofloxacin, btec = 1,2,4,5-benzenetetracarboxylate, 1,3-bdc = 1,3-benzenedicarboxylate) have been synthesized and characterized by elemental analyses, IR spectra, X-ray powder diffractions, TG analyses and single crystal X-ray diffraction. Compound 1 exhibits a (2D → 3D) interdigitated architecture that is first assembled from 2D wavelike (6,3) nets with side arms. Compound 2 is the first example of (2D → 3D) interdigitated metal–ppaH complex, which is constructed from sidearm-containing 2D layers of (4,4) topology. Compound 3 is built from 1D double chains with dangling levofloxacin ligands protruding from one side of the chain, and each pair of these double chains are interdigitated with each other to generate a perfect molecular zipper. By inspection of the structures of 1–3, it is believed that the short aromatic polycarboxylate ligands are important for the construction of interdigitated metal–quinolone complexes. The photoluminescent properties of compounds 1–3 have also been investigated.