Spectral, electrochemical and DFT studies of a trimetallic Cu II Derivative: Antimycobacterial and cytotoxic activity

The trimetallic Cu II derivative, [Cu 3 (L) 2 (ClO 4 ) 2 ] (1) [where H 2 L = N,N′-bis(salicylidene)-1,3-propanediamine] has been synthesized and characterized by different spectral techniques. In 1, the two terminal Cu II atoms are linked to the central Cu II atom by perchlorato anions and doubly phenoxido bridging. Both the square-pyramidal and octahedral geometries are observed in the two different types of Cu II centers which form the linear trimetallic unit. The EPR spectra in solid state reveal that there exists an exchange coupling among the Cu(II) atoms in the trinuclear unit having the two absorptions at g z = 2.204 and g x = g y = 2.032. We also conduct the DFT computational study which is in good accordance with EPR experimental data. The cyclic voltammogram of 1 shows a redox couple in the negative potential region, which is assigned to the possible reduction of Cu(II) to Cu(I) and further reduction of Cu(I) to Cu(0). Complex 1 exhibits anti-mycobacterial activity and considerable efficacy on M. tuberculosis H 37 Ra (ATCC 25177) and M. tuberculosis H 37 Rv (ATCC 25618) strains. The biological effect of 1 on the viability of human carcinoma cells has been evaluated using the MTT assay and the results indicate that the Cu(II) complex induces a decrease in cell-population growth with apoptosis.