Exploration of CH···π interactions involving the π-system of pseudohalide coligands in metal complexes of a Schiff-base ligand

A series of four mononuclear Schiff-base complexes, namely, [Zn(L)(NCS)2] (1), [Zn(L)(N3)2] (2), [Cu(L)(NCS)2] (3) and [Ni(L)(2bpy)(NCS)](ClO4) (4), [where L (9) = N,N-dimethyl-N'-(phenyl-pyridin-2-yl-methylene)-ethane-1,2-diamine and 2bpy = 2-benzoylpyridine] were synthesized with the aim of studying the role of different noncovalent weak interactions responsible for the crystal packing of the complexes. All of them were structurally characterized by x-ray diffraction anal. In addn. to conventional CH3···π and π···π interactions, the importance of unconventional C-H···π interactions in the crystal packing of compds. 1-4 was studied by Hirshfeld surface anal. and DFT calcns. In these unconventional C-H···π interactions, the π-system (electron donor) is provided by the pseudohalide coligands. The interactions formed by the π-system depend on the nature of the pseudohalide (N3, NCO, NCS or NCSe) as demonstrated by mol. electrostatic potential calcns. Addnl., the authors have explored the photophys. properties of these complexes. Finally, the authors have combined a search in the Cambridge Structural Database and DFT energy calcns. to analyze the rare ambidentate behavior of SCN within the same complex. [on SciFinder(R)]