Synthesis, crystal structure, DFT calculations, Hirshfeld surface analysis and molecular docking studies of a new manganese complex

Abstract

• Metal complexes with Schiff base ligands are interesting for biological and pharmacological applications. • A new manganese complex ( 3 ) has been synthesized and characterized. • Interesting hydrogen-bonding supramolecular synthons are present in ( 3 ) • Intermolecular electrostatic interactions play a crucial role in building supramolecular metal complexes. • Complementary experimental and theoretical methods are used for the study of (3) • Schiff base of (3) has an interesting biological activity. Mn II -based coordination compound [Mn II (L) 2 (NO 3 )(H 2 O) 3 ]NO 3 (3) has been synthesized with Shiff’s base N 2 -benzylidenyl isonicotinic acid hydrazide (2) and (Mn(NO 3 ) 2 ⋅4H 2 O). The compound is new and has been fully characterized by FT-IR, UV-visible, 1H and 13 C NMR spectroscopic techniques and single-crystal X-ray diffraction complemented with a quantum chemical study performed with DFT method. The compound crystallized in the monoclinic centrosymmetric P2 1 /n space group. The crystal structure of (3) exhibits a nitrate anion and a non-centrosymmetric complex cation [Mn II (L) 2 (NO 3 )(H 2 O) 3 ] + . In the molecular packing, the different entities are held together through intermolecular strong, weak and non-conventional O/N/C–H ···O hydrogen bonds, that found to be effective in stabilizing the three-dimensional network. Furthermore, the crystal structure of ( 3 ) contains interesting cyclic supramolecular homo and heterosynthons. Moreover, π–π stacking and N lone-pair …C–H intermolecular electrostatic interactions play a crucial role in building a supramolecular layered network. To better understand the contribution of different intermolecular interactions to the supramolecular assembly, Hirshfeld surface analysis was performed. The obtained results indicate that the main contributions are attributed to O—H···O, N—H···O and C—H···O interactions which are the primary giver the stabilisation in the crystal. The theoretical achievements were found in a good relation with the experimental structural analysis. The HOMO and LUMO energies and molecular electrostatic potential surface were derived from the same basis and the natural population Mulliken charge distribution analysis showed the different electron donors which coordinate with manganese. In addition to that, the molecular docking for (2) and (3) investigation with the 2X22 enzyme involved in Mycobacterium tuberculosis H37Rv have been conducted in order to check the biological activity of the Schiff base and its complex.