Molecular Packing of Group‐10 Metal Complexes of a Thiophene‐Fused Salophen Ligand Bearing a Wide π‐Surface

Naphthodithiophene‐fused salophen ligands and their Zn(II), Ni(II), and Pd(II) complexes were synthesized to investigate the effect of π‐surface extension on intermolecular self‐assembly. Single‐crystal X‐ray diffraction revealed that the Group 10 complexes adopt highly planar molecular structures and form head‐to‐tail π‐stacked dimers in the solid state, whereas the Zn(II) complex exhibits a distinct packing motif owing to its pentacoordinate geometry. Variable‐concentration NMR and UV–vis absorption measurements demonstrated pronounced self‐association of the Ni(II) and Pd(II) complexes in solution, affording dimerization equilibrium constants of 432 and 272 L mol −1 , respectively. In contrast, the corresponding salophen complexes lacking the naphthodithiophene unit showed only weak self‐association, indicating that extension of the π‐conjugated surface markedly enhances intermolecular π–π interactions. Furthermore, introduction of bulky tert ‐butyl substituents effectively suppresses dimer formation through steric hindrance. These results demonstrate that fusion of a naphthodithiophene unit provides an efficient molecular design strategy for controlling the self‐assembly behavior of square‐planar salophen metal complexes.