Palladium(II) complexes bearing N,O-bidentate Schiff base ligands: Experimental, in-silico, antibacterial, and catalytic properties

Abstract

Two N,O-bidentate ligands (1, 2), and their Pd(II) complexes, (1a, 2a) were synthesized and characterized via elemental analysis, IR, 1H and 13C NMR, magnetic moment and UV-Visible spectroscopy. Single crystal X-ray diffraction revealed that 1a crystallized as a monoclinic system in P2(1)/c space group, where two ligand 1 moieties coordinate to one palladium(II) centre through imine N and phenolic O donor atoms in a bis-bidentate manner, manifesting in a square planar geometry. The experimental spectral data of 1 and 1a were in good agreement with the calculated ones obtained in gas phase and polarizable continuum model (PCM) at the B3LYP/LANL2DZ level of theory. The experimental spectroscopic and Z-matrix data were also well reproduced with high correlation coefficients. The intercontact between 1a complex units was determined through Hirshfeld surface analysis and electrostatic potentials (ESP) maps, showing that the most predominant interactions were H…H (53.4%), C…H (25.3%) and O…H (12.6%). 1 and 1a were screened in-vitro to evaluate their antibacterial activity against two Gram-positive (S. aureus, S. haemolyticus) and two Gram-negative (P. aeruginosa, S. sonnei) bacteria. The antibacterial results revealed that 1a exhibited slight activity against Gram-negative bacteria, while the free ligand displayed no activity. The catalytic efficiency of 1a and 2a was evaluated in Mizoroki-Heck reaction of iodobenzene and methyl acrylate, and Suzuki-Miyaura reaction of iodobenzene and phenylboronic acid. Both catalysts resulted in good conversion percentages with 1a showing a more superior performance.