Manganese(II), Zinc(II) and Cadmium(II) complexes of 2 Aminopyridine and N Phenylanthranilic acid: synthesis, structural investigation and biological screening

Abstract

One of the objectives in coordination chemistry is the synthesis of molecules of various topologies that can exhibit interesting properties in several fields. Thus, three new supramolecular coordination compounds: [Mn(2-Apy)2(dca)2] (bis(2 aminopyridine)bis(𝜇1,5-dicyanamido)manganese(II)), [Zn3(H2O)2(NPA)6] (hexakis(μ2-2-anilinobenzoato)diaquatrizinc(II)) and [Cd(2-Apy)2(dca)2] (bis(2-aminopyridine)bis(𝜇1,5-dicyanamido)cadmium(II)) were synthesised in a water-ethanol mixture (1:5) and characterised by physico-chemical methods. The complexes obtained have different melting temperatures ranging from 162 to > 300 °C, temperatures different from those of the precursors used. This indicates that new compounds have been obtained. The results of elemental analysis show that the elemental contents present in the complexes are very close to the theoretical values, confirming the expected formulas of the complexes and purity.The IR spectra of the ligands and the complexes indicate good cohesion: the functional groups present on the spectra of the ligands are also present on those of the complexes, thus indicating that the ligands have been coordinated, notably the metal-nitrogen and metal-oxygen bonds.The X-ray diffractometry shows that the complexes of [Mn(2-Apy)2(dca)2] and [Cd(2-Apy)2(dca)2] are in a 1-D polymeric chain structure which crystallise in the monoclinic system with space group Cc. The complex of [Zn3(H2O)2(NPA)6] is a 3D trinuclear structure which crystallises in a triclinic crystal system with space group 𝑃1̅. The crystal structures obtained confirm the results of the elemental analysis, conductance measurements, and IR spectroscopy.Thermal analyses show that the complexes decompose in various steps in the temperature range of 50 – 650 °C with the loss of various fractions.The Hirsfeld surface analysis shows that C–H…π, H…H, and N…H/H…N intermolecular interactions for [Mn(2-Apy)2(dca)2] and [Cd(2-Apy)2(dca)2] constitute 82.0 % and 84.1 % respectively for the packing arrangement of the supramolecular crystal structure, while for [Zn3(H2O)2(NPA)6] C–H…π, H…H, and H…O/O…H interactions, it constitutes 96.4 %.DFT calculations show that [Zn3(H2O)2(NPA)6] possesses the lowest electronegativity value and that it is the best electron acceptor on one hand, and on the other hand, [Cd(2-Apy)2(dca)2] has been found to have the highest chemical reactivity amongst all due to its highest softness value. In vitro antimicrobial analyses show that globally, there is an enhanced biological activity of the complexes synthesised as compared to the ligands, which would mean that the coordination would increase the biological potency of the ligands. Both [Zn3(H2O)2(NPA)6] and [Cd(2-Apy)2(dca)2] complexes have shown activities against all microbial strains. [Mn(2-Apy)2(dca)2] shown no activity against the gram-negative bacteria S. typhi.Docking studies show that [Zn3(H2O)2(NPA)6] has potential for binding to the main protein in SARS-CoV-2 in a different location from Chloroquine, but with a higher binding strength. Which would indicate that it would be a potential candidate for the inhibition of SARS-CoV-2.