Coverage-dependent interactions at the organics-metal interface: Quinonoid zwitterions on Au(111)

The large intrinsic electric dipole of about 10 D of a p- benzoquinonemonoimine compound from the class of N-alkyldiaminoresorcinone (or 4,6-bisdialkylaminobenzene-1,3-diones, i.e., C₆H₂(· ·· NHR)₂(··· O)₂, where R = H) zwitterions is reduced considerably upon adsorption on Au(111) substrates. Scanning tunneling microscopy images reveal parallel alignment of adsorbed molecules within extended islands, leading to the formation of polarized domains. This is in contrast to the typical antiparallel alignment found in the bulk. High-resolution images show that the molecules form rows along the âŸ̈1Ì...01âŸ