Metal Complex Molecular Solids Showing Band-like Transport Driven by In Situ Ligand Exchange

Abstract

Transition-metalcomplexes exhibit excellent charge transport propertiesin solid films, rendering them promising for application in modernelectronics. Although the charge transport mechanism of metal complexsolids with multiple redox states is considered to be governed byself-exchange hole hopping, the effect of additives, such as Lewisbases, has not been identified. Herein, we describe the effect of4-tert-butylpyridine (TBP) on the charge transportmechanism and film properties of [Cu(dmbpy)(2)](2+/+) (dmbpy = 6,6 & PRIME;-dimethyl-2,2 & PRIME;-bipyridine)-based molecularsolids. The formation of [Cu(TBP)(4)](2+), excessTBP, and free dmbpy from the ligand-exchange reaction between [Cu(dmbpy)(2)](2+) and TBP increases the film conductivity andchanges the transport mechanism from hopping to band-like transportthrough a combination of chemical composition, film morphology, andcrystallographic changes. These findings advance our understandingof the fundamental properties of molecular metal complex solids andenable optoelectronic applications.