This study was aimed to synthesize and characterize two new copper(II) complexes, [Cu(phen)(Br-impi)](2+) (1) and [Cu(phen)(M-impi)](2+) (2) (where phen is 1,10-phenanthroline; Br-impi is 2-(2-(4-bromophenyl)-4- (pyridin-2-yl)-4,5-dihydro-1H-imidazol-5-yl)pyridine, andM-impi is 2-(2-(4-methoxyphenyl)-4-(pyridin- 2-yl)-4,5-dihydro-1H-imidazol-5-yl)pyridine), and to study their DNAbinding activity and cytotoxic activity. The interaction of complexes with ds-DNA has been investigated by spectroscopic methods, viscosity measurements, and agarose gel electrophoresis. The results indicate that complex 1 can bind to ds-DNA better than doescomplex 2 with binding constants 1.9 x 10(5)M(-1) and 3.9 x 10(4)M(-1), respectively.According to the UV titration method, complex 1 is capable of extractingethidium bromide molecules from DNA base pairs at lower concentrations than complex 2. In oxidative medium, both complexes produce complete degradationof plasmid DNA. Thecomplexes were screened against five human cell lines, namely A 549, PC-3, BEAS-2B, HCT-116 and MDZ-MB-231, and it was found that copper(II) complexes of trisubstituted imidazoleexhibited cytotoxic activity.