Synthesis, DNA binding, nuclease activity and cytotoxic studies of a wheel‐shaped octanuclear copper(II) complex based on 1,2,4‐triazole

The antitumor activity shown by many platinum complexes has produced a strong interest in research of new organometallic compounds . Among the metal compounds synthesized and tested, copper compounds have received considerable attention because of their cytotoxic activity against solid tumors. A novel wheel‐shaped octanuclear copper(II) complex with a 1,2,4‐triazole derivative ligand formulated as [Cu 8 L 4 ](ClO 4 ) 8 ⋅11H 2 O ( 1 ) (L = 3,5‐bis((bis(2‐hydroxylethyl)amino)methyl)‐4  H ‐1,2,4,‐triazole‐4‐amine) has been synthesized and structurally characterized. In 1 , eight Cu atoms are linked through 1,2,4‐triazole units and alkoxide bridges to form a centrosymmetric octanuclear Cu(II) metallomacrocycle. The interaction of complex 1 with calf thymus DNA has been studied using UV absorption, fluorescence and circular dichroism spectroscopies, viscosity measurements and cyclic voltammetry. The apparent binding constant ( k app ) value for 1 is 1.59 × 10 5  M −1 . Furthermore, complex 1 displays efficient oxidative cleavage of supercoiled DNA in the presence of external agents, the rate constant for the conversion of supercoiled to nicked DNA being 2.67 × 10 − 5  s −1 . Interestingly, cytotoxicity studies on the MCF‐7 human breast cancer cell line show that the IC 50 value of 1 is less than that of cisplatin for the same cell line, revealing that it has the potential to act as an effective metal‐based anticancer drug. Copyright © 2016 John Wiley & Sons, Ltd.