Five water-soluble zwitterionic copper(II)-carboxylate polymers: role of dipyridyl coligands in enhancing the DNA-binding, cleaving and anticancer activities.

Five water-soluble zwitterionic copper-carboxylate polymers were prepared from the reaction of N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide (H3CmdcpBr) with Cu(NO3)2 in the presence of NaOH by modulating the temperature, solvent and ancillary dipyridyl ligands. These complexes include a 1D ladder-shaped polymer {[Cu3(Cmdcp)2(OH)2(H2O)2]·H2O}n () formed in H2O at room temperature, and a 2D network polymer {[Cu(Cmdcp) (H2O)2]·2H2O}n () isolated in H2O at 135 °C. At 100 °C in H2O/DMF, the same reaction in the presence of an additional 2,2'-bipyridine (bipy) gave a 2D zwitterionic complex {[Cu(Cmdcp)(bipy)]·3H2O}n () together with a 1D double-stranded polymer {[Cu(Cmdcp)(H2O)2]·H2O}n () as a minor product. The replacement of bipy with phenanthroline (phen) afforded a 1D zigzag polymer chain {[Cu(Cmdcp)(phen)(H2O)]2·9H2O}5 (). All these complexes were characterized by IR, elemental analyses and single crystal X-ray crystallography. Agarose gel electrophoresis (GE) and ethidium bromide (EB) displacement experiments indicated that complex exhibited the highest pBR322 DNA cleaving ability with the catalytic efficiency (kmax/KM) of 14.80 h(-1) mM(-1) and the highest binding affinity toward calf-thymus DNA. The MTT assay indicated that complex showed significant inhibitory activity toward the proliferation of several tumor cells. Its IC50 value was at micromolar level and lower than those of cisplatin and complexes , especially toward resistant lung adenocarcinoma cell A549.