Synthesis and biological evaluation of copper(ii) pyrenethiosemicarbazone

Abstract

Pyrenethiosemicarbazone (PyTSC) and its copper(II) complex (CuPyTSC) have been synthesized and characterized by elemental analysis, ¹H-NMR, IR, ESI-MS, cyclic voltammetry, UV-Visible and fluorescence spectroscopy. Both the compounds interact with calf thymus (CT) DNA via intercalation with apparent binding constants, K_b, of the order of 10⁵. CuPyTSC shows better photo-induced DNA cleavage of plasmid pBR322 DNA (74%) than PyTSC (14%). Mechanistic investigations revealed the involvement of singlet oxygen species in the DNA cleavage by both the compounds. DFT calculations demonstrated more efficient generation of singlet oxygen by CuPyTSC with a decreased HOMO–LUMO gap (0.332 eV) than PyTSC (0.629 eV). The protein binding ability has been monitored using Bovine Serum Albumin (BSA). The compounds show green fluorescence revealing their uptake by the cells under a fluorescence microscope. CuPyTSC displayed better cytotoxic activity on photoexposure to B16F10 melanoma cells.