Steric effect on construction of extended architectures of Ni(II) complexes directed by intermolecular C-H···F and C-H···O interactions

Five new Ni(II) complexes with pyridine carboxamide ligands have been synthesized and the crystal structures of three of the complexes were determined. Strong distortion effects of 6-methyl substitution were observed in the complexes with 6-methyl-substituted pyridyl bpb ligands. The C-H···F and C-H···O hydrogen bond interactions build extended architectures in the crystals studied. This result suggests that the steric effect of 6-methyl substitution plays an important role in the distortion of the structure, and the 6-methyl substitution can facilitate hydrogen bond interactions between methyl hydrogen atoms and O(carbonyl) or F atoms. Twelve Ni(II) complexes, including seven complexes reported previously, show reversible redox behavior, implying that the reduced Ni(I) state of each complex is stable in the time scale of CV measurement. The steric effect of R₁ substituent and the electronic effects of X₁ and X₂ groups were found to be the main factors contributing to the shift of the redox potential of the Ni(II) complexes