Adsorption of TCNQH-functionalized quinonoid zwitterions on gold and graphene: evidence for dominant intermolecular interactions

Abstract

We experimentally investigate the electronic structure of the strongly dipolar, quinonoid-type molecule obtained by TCNQH-functionalization (TCNQH = (NC)2CC6H4CH(CN)2) of (6Z)-4-(butylamino)-6-(butyliminio)-3-oxocyclohexa-1,4-dien-1-olate C6H2(NHR)2(O)2 (where R = n-C4H9) to be very similar after deposition from solution on either graphene or gold substrates. These zwitterion adsorbate thin films form structures that are distinct from those formed by related quinonoid molecules previously studied. We argue that adsorbate–adsorbate interactions dominate and lead to a Stranski–Krastanov ‘island growth’ mechanism.