Self-assembled two-dimensional nanoporous molecular arrays and photoinduced polymerization of 4-bromo-4′-hydroxybiphenyl on Ag(111)

Self-assembled two-dimensional molecular arrays and photoinduced polymerization of 4-bromo-4′-hydroxybiphenyl on Ag(111) were studied using low-temperature scanning tunneling microscopy combined with density functional theory calculations. Square-like self-assembled structures of 4-bromo-4′-hydroxybiphenyl stabilized by intermolecular hydrogen and halogen bonds were transformed into hexagonal nanopores of biphenyl biradicals by 266 nm UV laser irradiation at 80 K. The biradicals further coupled to each other and formed covalently linked polyphenylene polymer chains at room temperature.