Effect of the Thermal Decomposition and In Vitro Antimicrobial Activity of Mixed Ligand Copper(II) Complexes

Abstract

The author aimed to determine the activation energy for the thermal decomposition on mixed ligand copper(II) complexes of the type [Cu(Lⁿ)(CQ)(H₂O)₂].xH₂O (where L¹ = 2-bromo-7-hydroxy-10,11-dihydroindeno[5,4-c]chromen-6(9H)-one, L² = 2-bromo-7-hydroxy-9,10,11,12-tetrahydro-6H-naphtho[2,1-c]chromen-6-one, L³ = 5-bromo-14-hydroxy-7,8-dihydro-1H-phenanthro[2,1-c] chromen-1-one, and x = 4, 5, 3) were studied at room temperature. All the compounds have been characterized by elemental analysis, magnetic susceptibility, FT-IR, ¹H-NMR, ¹³C-NMR, electronic spectra and FAB-mass spectrometry. Electronic spectra and magnetic susceptibility measurements indicate octahedral stereochemistry. TGA and DSC determined thermal stability, order of kinetics, heat capacity, and activation energy of thermal degradation for these complexes. Order of stability of complexes was found to be [Cu(L¹)(CQ)(H₂O)₂].4H₂O > [Cu(L²)(CQ)(H₂O)₂].5H₂O > [Cu(L³)(CQ)(H₂O)₂].3H₂O. The ligands, metal salts, complexes, control, and standard drug were tested for their in vitro antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, and Bacillus substilis. The metal complexes exhibit good activity against bacterial strains compared with parental compounds and moderate compared with the standard drug (Clioquinol).

Keywords:

• copper(II) complexes
• FTIR
• in vitro antibacterial
• kinetic parameters
• mass spectrometry
• TGA
• thermal studies

Acknowledgments

The author is grateful to Prof. K. D. Patel, chemistry department, V. P. and R. P. T. P. Science College, Sardar Patel University, for providing the necessary laboratory facilities. Analytical facilities provided by the Sophisticated Instrumentation Centre for Applied Research and Testing (SICART), Vallabh Vidyanagar, Gujarat, India are gratefully acknowledged.