Molecular docking-assisted investigation of Pd(II) complexes carrying "SNS" pincer-type pyridine-thioether ligand as potential drug candidates against COVID-19.

The coronavirus disease 2019 (COVID-19) pandemic has posed a threat to public health throughout the world since the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) was discovered in late 2019. Since the beginning of the pandemic, scientists have done a tremendous amount of work in this area. However, among these studies, the investigation of the effect of newly synthesized compounds against coronavirus is rather weak. Examining the newly synthesized compounds with a computer-assisted molecular docking study provides quite an advantage in terms of the estimation and analysis of the biochemical activity and binding affinity of existing synthesized compounds against a biological target in a labor, time, and cost-saving way. In this study, the SNS pincer type 2,6-bis[[(4-methylphenyl)thio]methyl]pyridine ligand(L) (1) and its novel Pd(II) complexes ([Pd(κ2-L)(OAc)2]·3H2O (2) and [Pd(κ2-L)Cl2]·3H2O (3)) were synthesized and characterized by using FT-IR, UV-Vis, NMR, mass and elemental analysis techniques. The synthesized Pd complexes exhibited a square planar structure. The compounds were found to have non-electrolytic behavior. In the meantime, in silico investigations have defined and justified interaction processes between these molecules and Pd(II) at the atomic level. Furthermore, using molecular docking against target proteins of SARS-CoV-2, the efficiency of the SNS pincer type ligand and its Pd (II) complexes produced was studied and discussed for the first time. The experimental data has been supported and illuminated using computational visual methods and molecular docking, and the findings produced indicate compatibility. The binding energy values of the relevant compounds on the four protein model structures of SARS-CoV-2 (Main Protease, Papain-like protease, RdRp without RNA, and RdRp with RNA) are represented. Compound 2 ([Pd(κ2-L)(OAc)2]·3H2O) is the structure that exhibits the highest biochemical activity. According to all of the docking studies, Papain-like protease is the SARS-CoV-2 protein with which the three compounds exhibit mutual interaction. The compound 2 structure, in particular, is the most effective in terms of structural and interaction with the targets, as well as binding orientations.

Synthesis of novel chiral metal complexes derived from chiral thiosemicarbazide ligands as potential antioxidant agents.

Two new chiral thiosemicarbazide ligands and their Cu (II), Ni (II), Pd (II), and Zn (II) complexes were synthesized and characterized by nuclear magnetic resonance (NMR) (only for ligand), Fourier transform infrared (FT-IR), ultraviolet visible (UV-Vis), mass, and elemental analysis. The antioxidant activity of ligands and their metal complexes was examined. It was found that the antioxidant activity of metal complexes was better than their ligands. In addition, the antioxidant activity, as reflected by free radical scavenging, was evaluated. Besides, Pd (II) complexes exhibited better antioxidant activity than Ni (II), Cu (II), and Zn (II) complexes. Therefore, complexes (3a-Pd and 3b-Pd) can be used as an antioxidant agent or antioxidant test standard.

Palladium nanoparticles decorated on amine functionalized graphene nanosheets as excellent nanocatalyst for the hydrogenation of nitrophenols to aminophenol counterparts.

We reported the improved catalytic property of Pd (0) nanoparticles decorated on amine-functionalized graphene nanosheets (Pd/GNS-NH2) for the hydrogenation of nitrophenol derivatives in the presence of NaBH4 at moderate conditions. Pd/GNS-NH2 nanocatalyst was synthesized by the deposition-reduction method. Sundry techniques such as ICP-OES, P-XRD, XPS, TEM, HR-TEM and EDX have been applied to explain the structure and morphology of the Pd/GNS-NH2 nanocatalyst. The results show that the Pd (0) nanoparticles are perfectly dispersed on the surface of the GNS-NH2 support material (dmean = 1.38-2.63 nm). The catalytic activity of the Pd/GNS-NH2 nanocatalyst was tested in the hydrogenation of nitrophenol derivatives in water in the presence of NaBH4 as reductant and the excellent activity of nanocatalyst have been detected against 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,4,6-trinitrophenol derivatives with 116.8, 65.9, 42.8 and 11.4 min-1 initial TOF values, respectively. Another important point is that the nanocatalyst has very high reusability performance (at 5th reuse between 71.5 and 91.5%) for the hydrogenation of nitrophenols. Finally, catalytic studies have been carried out at various temperatures to calculate the Ea, ΔH≠ and ΔS≠.