Rationally designed, polymeric, extended metal-ciprofloxacin complexes

Reactions of the antimicrobial fluoroquinolone ciprofloxacin (cfH) with metal salts in the presence of aromatic polycarboxylate ligands or under basic conditions produce fourteen new metal-cfH complexes, namely, Ba2(cf)2(1,4-bdc)(H2O)2] x H2O (1), Sr6(cf)6(1,4-bdc)3(H2O)6] x 2H2O (2), M2(cfH)2(bptc)(H2O)2] x 8H2O (M = Mn3 and Cd4), M(cfH)(1,3-bdc)] (M = Mn5, Co6, and Zn7), Zn2(cfH)4(1,4-bdc)](1,4-bdc) x 13H2O (8), Ca(cfH)2(1,2-Hbdc)2] x 2H2O (9) and M(cf)2] x 2.5H2O (M = Mn10, Co11, Zn12, Cd13, and Mg14) (1,4-bdc = 1,4-benzenedicarboxylate, bptc = 3,3',4,4'-benzophenonetetracarboxylate, 1,3-bdc = 1,3-benzenedicarboxylate, 1,2-bdc = 1,2-benzenedicarboxylate). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. The structures of 1 and 2 consist of unique two-dimensional arm-shaped layers. Compounds 3 and 4 are isostructural and feature one-dimensional structures formed from the interconnection of M2(cfH)2(H2O)2] dimers with bptc ligands. Compounds 5-7 are isostructural and contain double-chain-like ribbons constructed from M2(cfH)2(CO2)2] dimers and 1,3-bdc. Compound 8 consists of a pair of Zn(cfH)2]2+ fragments bridged by a 1,4-bdc into a dinuclear dumbbell structure. Compound 9 is a neutral monomeric complex. To the best of our knowledge, compounds 1-9 are the first examples of metal-quinolone complexes that contain aromatic polycarboxylate ligands. Compounds 10-14 are isostructural and exhibit interesting two-dimensional rhombic grids featuring large cavities with dimensions of 13.6x13.6 A. Up to now, polymeric extended metal-cfH complexes have never been reported.