An electrically conductive dinuclear double helicate Al(iii) complex for the fabrication of a Schottky diode

The crystallographic elucidation of a dinuclear aluminium(III) helicate (1) consisting of the biphenyl-derived two-arm-containing amido Schiff base ligand bis(2-hydroxybenzylidene)-[1,1'-biphenyl]-2,2'-dicarbohydrazide (ligand H₄L) is reported. The X-ray single crystal diffraction studies of complex 1 reveal that it crystallizes in the triclinic space group P-1. Each Al³⁺ ion is coordinated to four oxygen and two nitrogen atoms from the two terdentate ligands to form an octahedral geometry. Furthermore, several types of intra-/inter-molecular interactions, including H-bonding, C-H⋯O weak interactions, and π⋯π interactions, stabilize its crystal lattice, leading to a supramolecular polymeric structure. The electrical performances of H₄L and 1 are investigated in a metal-semiconductor (MS) junction. A significant enhancement in electrical conductivity and improved Schottky barrier diode (SBD) parameters are observed for 1 compared to its precursors. The I-V characteristics demonstrated that, upon complexation with the Al(iii) ion, conductivity increased by twice the magnitude (H₄L: 4.02 × 10^-4 Sm^-1; complex 1: 8.70 × 10^-4 Sm^-1) with an improved diode rectification ratio, which can be corroborated to the supramolecular polymeric structure of 1. Measurements of the optical bandgap as well as the HOMO-LUMO gap computed by density functional theory (DFT) calculations confirm the semiconducting properties of 1. Moreover, the theoretical DOS/PDOS plots provide evidence for the Schottky diode function of the complex.