Effect of para-substituents in benzoate ligands on X⋯X and π⋯π interactions governing Schottky behaviour in Cd(II) compounds.

We present the synthesis of two coordination compounds, [Cd2(4-Clbz)4(4-avp)4] (1) and [Cd2(4-Brbz)4(4-avp)4] (2), employing the N-donor ligand 4-[2-(9-anthryl)vinyl]pyridine (4-avp) in combination with the O-donor ligands 4-chlorobenzoate (4-Clbz) and 4-bromobenzoate (4-Brbz), respectively. Structural analysis revealed that X⋯X [X = Cl for (1) and Br for (2)], π⋯π, C-H⋯X, C-H⋯π, and X⋯π interactions play significant roles in directing the supramolecular assembly and stabilizing the crystal lattice. Notably, both compounds 1 and 2 exhibit semiconducting characteristics and operate as Schottky barrier diodes. However, compound 1 shows a superior electrical response and enhanced Schottky diode performance over compound 2, which is associated with lower series resistance and more effective through-space carrier hopping between the active chromophores. Density functional theory (DFT) calculations substantiate the direct-gap semiconducting behavior and demonstrate that the frontier electronic states are dominated by the π-stacked 4-avp ligands, with negligible direct contribution from the 4-halobenzoate (4-Xbz) units. Thus, the 4-Xbz ligands and their secondary contacts (X⋯X and X⋯π) serve as structure directing agents that modulate the spatial orientation of the conjugated 4-avp framework and film organization rather than functioning as direct conducting channels. Molecular DFT analyses, including molecular electrostatic potential (MEP), quantum theory of atoms in molecules (QTAIM), and natural bond orbital (NBO) methods, elucidate the subtle differences in the supramolecular interactions that govern crystal packing. These outcomes highlight the importance of peripheral ligand modification in indirectly altering charge transport and device performance in d10 metal-based systems.