Presence of edge-to-face aromatic interaction in bis[1,2-bis(4-alkylphenyl)ethanedione dioximato]nickel(II) complexes and evaluation of the fastener effect

Bis[1,2-bis(4-methylphenyl)ethanedione dioximato]nickel(II), [Ni{(C1)2dpg}2] (1), was found to exhibit shift in diffuse reflectance spectra from the corresponding non-methyl species. Characterization by X-ray crystal structural analysis on 1 and bis[1,2-bis(4-n-hexylphenyl)ethanedione dioximato]nickel(II), [Ni{(C6)2dpg}2] (2), revealed the presence of the edge-to-face aromatic interactions caused by the electron-donating effect of the methyl and hexyl groups. The Ni(dpg)2 units of complex 2 stack (staggered by 90°) at alternate intervals of 3.151 Å and 3.253 Å. Thus, the shift in the d–p transition of 2 was found to contain 43% of the effect of the edge-to-face aromatic interaction, together with 57% of the reported fastener effect.