Linking molecules to metal surfaces with covalent bonds

Covalent linkage between organic species and metal electrodes is appealing for constructing robust and highly-conducting molecular junctions. Strategies for creating covalent organic/metal contacts often involve chemical reactions, which not only offer tools for circuitry design, but also provide rich information about surface chemistry and reaction mechanism at a molecular and atomic level. This review showcases methods including transmetalation reactions employing chemical structures such as organostannanes and boronic acids, and electrochemical redox approaches using diazonium terminal groups, as well as amines and imine radicals, for forming C-Au and N-Au bonds with Au electrodes. Other novel strategies such as C(sp²)-C(sp²) bond cleavage in cycloparaphenylenes for C-Au bonds, and the well-established thiol and acetylene chemical groups for forming S-Au, S-Ag, C-Au and C-Ag bonds, are also discussed.