Synthesis, crystallization and Hirshfeld surface analysis of transition metal carboxylate pentapyridines

A new compound 2,6-bis(1,1-di(pyridin-2-yl)ethyl)isonicotinic acid (Py5Me(2)COOH) was successfully synthesised and metalated with nickel, cobalt and copper to give the corresponding complexes [Co(Py5Me(2)COO(-))(OH-)](1+) (1), [Ni(Py5Me(2)COO(-))(H2O)](1+) (2) and [Cu-4(Py5Me(2)COO(-))(2)(H2O)(4)(OH-)(2)](4+) (3). The complexes were characterized through HD-MS, FT-IR and UV-vis spectroscopic methods. Crystals suitable for single X-ray diffraction were successfully grown and reveals complex 1 and 2 maintain the conventional distorted octahedral configuration. Complex 3 resulted in the formation of a square pyramidal tetra-copper di-ligand structure. Hirshfeld surfaces mapped with d(norm) and shape index functions were used to give further information on interaction types within the crystal. Analysis of the 2D fingerprint plots shows the dominant interactions within the crystal packing to be HMIDLINE HORIZONTAL ELLIPSISH and OMIDLINE HORIZONTAL ELLIPSISH contacts, with complex 1 forming a three-dimensional hydrogen bonded polymer. Crystal packing in complex 3 is strongly influenced by fluorine interactions; (HMIDLINE HORIZONTAL ELLIPSISF) and the packing structure of complex 2 is shaped by pi based interactions. The orientation of these contacts reveals the structure directing effects of the carboxylate, with the weaker aromatic interactions arranging to give priority to the stronger and more directional hydrogen bonds.