A Ni(II) chetale of an unsymmetrical N2O3 donor ligand and its use as flexidentate metalloligand to synthesise heterometallic Ni(II)-Mn(II) complexes: Recurrent CH⋯π and π-stacking motifs in the structures

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An attempt to synthesis complexes of a N2O3 donor unsymmetrical Schiff base ligand, obtained from the condensation of 2,2-dimethyl-1,3-propanediamine with o-hydroxyacetophenone and o-vanillin via modified Edler's method yielded a mononuclear Ni(II) complex, [NiL]·1.5H2O·0.5CH3OH (1), where H2L = N-(α-methylsalicylidene)-N′-(3-methoxysalicylidene)-2,2-dimethyl-1,3-propanediamine. Three heterometallic Ni(II)-Mn(II) complexes, [(NiL)2Mn(H2O)2](ClO4)2·2H2O (2), [(NiL)MnCl2] (3) and [(NiL)Mn(NCS)2(H2O)]·[NiL] (4), have been isolated upon reaction of complex 1 with Mn(II) ions in presence respective co-anions, of which two are discrete complexes while third is a co-crystal. Single crystal X-ray crystallography revealed that Ni(II) centre is four coordinated in square planar environment in all complexes, whereas the geometry of Mn(II) centre is distorted octahedral in complexes 2 and 4, and distorted trigonal bipyramidal in 3. Structural differences have been rationalized by density functional theory (DFT) calculations. All the complexes exhibit recurrent π-stacking and CH⋯π motifs in solid state which have been characterized by molecular electrostatic potential (MEP) surface calculations and non-covalent interaction plot.