Charge transport and luminescent properties of C6F5Cu(py) and their relationships with cuprophilic interactions: a density functional theory investigation

Weak interactions between copper atoms so called cuprophilic interactions, lead to the supramolecular stacks of C6F5Cu(py), which possess unique luminescent and charge transport properties. First-principle band-structure calculations have been used to investigate the relationship between its charge transport property and cuprophilic interactions for the first time. The valence bandwidth was found three times larger than the conduction bandwidth. Meanwhile, the effective mass of hole is 0.46 m(0), which is only one-third of the electron, and much smaller than that of the pentacene. Thus, C6F5Cu(py) would become a promising candidate for hole transport material. The analysis based on density of states and band structure shows that holes transport mainly along the direction of cuprophilic interactions (c-axis) and cuprophilic interactions are in favor of hole transport. Thus, the cuprophilic interactions play an important role in determining charge transport. By the replacement of copper atoms with silver and gold atoms, the results show that there are close relationships between the metallophilic interactions and transport ability, i.e., the stronger metallophilic interactions are, the better hole transport ability is. The solid state emission of C6F5Cu(py) is attributed to the monomer rather than the dimer. This emission is assigned as the metal-to-ligand charge transfer (MLCT), and combined with some contributions from ligand-to-ligand charge transfer (LLCT).