Three coordination polymers of 5-aminoisophthalic acid with similar benzimidazole derivative ligands: synthesis, structure and DNA-binding studies

Three novel coordination polymers, [Co(NH2-Aip)(H(2)Bibim)](n) (1), [Co(NH2-Aip)(HBibimop)](n)center dot nH(2)O (2) and [Mn(NH2-Aip)center dot H2O](n)center dot 2nH(2)O (3) with NH2-Aip and similar benzimidazole derivative ligands (NH2-Aip 5-aminoisophthalic acid, H(2)Bibim = 2,2'-bibenzimidazole and HBibimop = 1,3-bis(benzimidazol-2-yl)-2-oxapropane), have been synthesised under hydrothermal conditions and structurally characterised by single-crystal X-ray diffraction analysis, elemental analysis and IR spectroscopy. 5-Aminoisophthalic acid ligand adopts mu(2)-, mu(3)- and mu(4)-bridge coordination fashion and benzimidazole derivatives exist as terminal-and bridge-mode in complexes 1-3. The intricate hydrogen bonds and pi-pi stacking interactions in supramolecular framework are discussed. Using the combination of ultraviolet-visible absorption titration and fluorescence spectra, the experimental results show that complexes 1 and 2 bind to DNA in an intercalative mode and their DNA-binding constants (K-b) are also found.