Palladium(II) complexes of thiobenzamide derivative ligands: Synthesis, crystal structure, supramolecular architecture, Hirshfeld surface analysis, and in vitro antibacterial and antifungal activities

Abstract

Three thiobenzamide derivative ligands and their palladium complexes were synthesized. The synthesized compounds were characterized by several instrumental methods, such as 1H NMR, 13C NMR, and FT–IR. Additionally, the appropriate crystal of the [PdIICl2(L3H)2] complex was analyzed to determine the molecular structure. The single–crystal X–ray diffraction (SC–XRD) revealed that [PdIICl2(L3H)2] complex has a monoclinic crystal system, C2/c space group, a = 12.2969(11) Å, b = 18.7618(16) Å, c = 16.899(2) Å, β = 97.875(4)°. The intramolecular and intermolecular interactions in the crystal structure led to the formation of two synthon systems. In addition, a quantitative investigation of the noncovalent interactions in the structure was carried out through the utilization of Hirshfeld surface and 2D–fingerprint plot analyzes. Analysis of [PdIICl2(L3H)2] using 2D fingerprint analysis revealed a range of intermolecular interactions responsible for its stabilization. Among these interactions, intermolecular H···H (51.90%), Br···H/H···Br (16.00%), and Cl⋯H/H···Cl (10.40%) were found to be the most prominent types of interaction. The 3D layout of the crystal packing was evaluated during the energy framework computations, demonstrating that the electrostatic energy framework had a significant impact over the dispersion energy framework. Antibacterial and antifungal activities of the thiobenzamide derivative palladium complexes were also tested against Gram–positive (E. faecalis, S. aureus, B. subtilis, and S. pneumonia) and Gram–negative (P. aeruginosa and E. coli) bacterises and against fungi (C. glabrata and C. albicans). Palladium complexes exhibited to be more effective against fungi than against bacteria according to the MIC values. Particularly, [PdIICl2(L2H)]2 complex showed an excellent antifungal effect among the other palladium complexes, with low MIC values of 3.90 and 7.81 μg/mL against C. glabrata and C. albicans fungi, respectively.