Trinuclear nickel (II) string complexes and copper (II) coordination polymer with pyrazine modulated unsymmetrical dipyridylamino ligand: Synthesis, structure and bioactivity properties with molecular docking

The unsymmetrical pyrazine-modulated ligand, N-(pyridine-2-yl)pyrazin-2-amine (Hppza) (1), its 1D straightchain copper (II) coordination polymer [Cu2(Hppza)2 center dot(NO3)4]n (2) and trinuclear metal string [Ni3(mu 3ppza)4Cl2] (3) and [Ni3(mu 3-ppza)4(NCS)2] (4) complexes have been successfully synthesized and structurally characterized. The free ligand Hppza (1) exhibits anti-syn conformation. In an asymmetric unit of 2, there are two kinds of Cu(II) atoms, both of which have elongated octahedral coordination geometry, and the copper(II) centers are linked by oxygen atoms of one nitrate anion. There are only minor differences in Ni...Ni bond lengths between pyrazine-modulated ligand complexes of [Ni3(mu 3-ppza)4x2] (X = Cl-(3), NCS- (4)) and their unmodulated analogs, while the distances between the terminal nickel atoms and the axial ligands 3 and 4 are shorter. The results of magnetic susceptibility measurements showed an antiferromagnetic exchange constant (J) of about J = -199.2 cm-1 for 3 and J = -178.0 cm-1 for 4. The electrochemical properties of nickel strings of Hppza differ significantly from their unmodulated counterparts. The activities of ligands and their metal complexes against various proteins that are AChE (PDB ID: 4M0E), BChE (PDB ID: 5NN0), alpha-Gly (PDB ID: 1UAS), hCA I (PDB ID: 2CAB), and hCA II (PDB ID: 3DC3) were compared, and then the ADME/T properties of molecules were examined. Afterward, the interactions occurring in the docking calculation were examined in detail with the Protein-Ligand Interaction Profiler (PLIP) service. These complexes were inhibitors of BChE, hCA I and II, alpha-glycosidase and AChE enzymes for complex 3 and 5 with Ki values of 12.65 and 42.95 mu M for hCA I, 3.64 and 15.84 mu M for hCA II, 5.44 and 50.07 mu M for BChE, 15.85 and 4.77 mu M for alpha-glycosidase and 8.58 and 86.24 mu M for AChE, respectively.