Ultrafast Charge Transfer through Noncovalent Au-N Interactions in Molecular Systems

Charge transfer through noncovalent interactions is crucial to a variety of chemical phenomena. These interactions are often weak and nonspecific and can coexist, making it difficult to isolate the transfer efficiency of one type of bond versus another. Here, we show how core-hole clock spectroscopy can be used to measure charge transfer through noncovalent interactions. We study the model system 1,4-benzenediamine molecules bound on an Au surface through an Au-N donor-acceptor bond as these are known to provide a pathway for electronic conduction in molecular devices. We study different phases of the molecule/Au system and map charge delocalization times from carbon and nitrogen sites on the molecule. We show that charge delocalization across Au-N donor-acceptor bond occurs in less than 500 as. Furthermore, the Au-N bond also enhances delocalization times from neighboring carbon sites, demonstrating that fast charge transfer across a metal-organic interface does not require a covalently bonded system.