Comprehensive structural {single crystal X-raydiffraction, spectroscopic & DFT computational simulation} and biological {in vitro DNA binding & antibacterial} studies of polymeric copper(Ⅱ)-based imidazole drug entity

Abstract

A polymeric tetrakis N-imidazole copper(II) sulphate complex [Cu(imidazole)4(SO4)]n1, was synthesized and thoroughly characterized by various spectroscopic techniques, elemental analysis and single crystal X-ray crystallography. X-ray diffraction analysis confirmed that polymer complex 1 crystallized in a monoclinic C2/c space group possessing the lattice constants, a = 9.2213(1) Å, b = 17.6062(3) Å, c = 10.5710(2) Å, α = γ = 90˚ and β = 93.561˚ (1) per unit cell. Hirshfeld surface and DFT calculations were executed to simulate the electronic ground state energies in gas phase which showed that the HOMO and HOMO–1 were distributed on the axially coordinated SO42– moiety and considerable amount of electron density was present on Cu(II). Absorption and emission spectroscopic techniques were used to investigate the binding interaction of the copper(II) imidazole complex with the therapeutic target ct-DNA. The results suggested that the complex 1 binds to the ct-DNA through an electrostatic mode. The gel electrophoresis experiments of 1 were carried out with plasmid pBR322 which revealed that the polymer complex could unwind the plasmid DNA at 30 μM micromolar concentration via discernible oxidative cleavage pathway. Molecular docking studies were also carried out to support the results of DNA binding experiments. In addition, the antimicrobial potential of polymer complex was evaluated against various key pathogens viz., B. subtilis, E. coli, K. pneumonia and S. aureus. Antibiofilm behaviour of the complex 1 was examined against E. coli and S. aureus. The results demonstrated that 1 could act as an active antibacterial agent as it inhibited the bacterial growth in agar plates very efficiently.