Noncoordinating Anions as Key Modulators of Supramolecular Structures, Optical and Electrical Properties in Nickel(II) Complexes

This study explores the synthesis, structural characterization, and examination of two nickel(II) complexes, [Ni(N₃L₁)₂](NO₃)₂ (complex 1) and [Ni(N₃L₁)₂](ClO₄)₂ (complex 2), using the newly synthesized organic heterocyclic chelating ligand N₃L₁ [4-imidazole-2,6-di(pyrazinyl)pyridine]. Through single-crystal X-ray diffraction, we have detailed the crystal structures of these complexes, highlighting their distorted octahedral geometries and diverse supramolecular interactions including π···π stacking, anion···π, and hydrogen bonding. These interactions crucially influence the formation of distinct one- and two-dimensional supramolecular architectures. Density functional theory (DFT) calculations were utilized to probe these noncovalent interactions, revealing insights into their stereoelectronic influence and stability in the solid state. Additionally, the electronic properties of the complexes were explored through their electrical characterizations in Schottky diodes, which suggest the potential of these complexes in Schottky diode based electronic devices applications. Notably, complex 2, incorporating perchlorate anions, exhibited better electrical properties than complex 1. This work aims to elucidate the role of noncoordinating counteranions in the structural integrity and photophysical behavior of these complexes, while also providing a structure–function correlation through detailed theoretical analysis.