Synthesis, structural features, antibacterial behaviour and theoretical investigation of two new manganese(III) Schiff base complexes

Two discrete manganese(III) coordination compounds, [Mn(L)(OCN)1](2) (1) and [Mn(L')(H2O)(2)] [DNBA]center dot DMF center dot H2O (2) bearing in situ generated Schiff base ligands H2L [H2L=N,N'-o-phenylenebis(salicylaldimine)] or H2L' [H2L' = N,N'-bis(salicylidene)ethylenediamine], were easily prepared by treating Mn (CH3COO)(2)center dot 4H(2)O with salicylaldehyde and o-phenylenediamine (for 1) or ethylenediamine (for 2), and in the presence of supporting cyanate ligands or 3,5-dinitrobenzoate (dnba) counter anions, respectively. The obtained products were isolated as air-stable crystalline solids and were fully characterized by spectroscopic methods, single-crystal X-ray diffraction, topological analysis, as well as theoretical methods. The X-ray diffraction of the compound 1 reveals that the structure is dimeric with phenolic oxygen atom acting as bridge between two symmetrically equivalent Mn(III) atoms. The structure of 2 contains mononuclear cationic [Mn(L')(H2O)(2)] units along with a 3,5-dinitrobenzoate anion and crystallization DMF molecule. Structural analysis indicates a distorted octahedral geometry for both complexes. Intermolecular hydrogen bonding and pi-pi stacking interactions are present in the lattice and play an important role in cohesion of the structures. Topological analysis of the compound 2 reveals a binodal 3,4-connected underlying 2D net with the 3,4L13 topology. Noncovalent interactions were investigated in terms of energies and geometries using theoretical calculations. Fluorescence and antibacterial properties of 1 and 2 were also investigated and discussed. (C) 2018 Elsevier Ltd. All rights reserved.