Guanine Assemblies on the Au(111) Surface: A Theoretical Study

It was found previously [Small2009, 5, 1952 and Angew. Chem., Int. Ed.2005, 44, 2270] that guanine molecules when assembled in a vacuum on the Au(111) surface at room temperature form a hydrogen-bonded network consisting of guanine quartets of the same chirality; this was supported by ground-state density functional theory (DFT) gas-phase calculations. In this Article, we re-examine this system and show that many more (almost equally stable) both homo- and heterochiral structures are possible; however, the homochiral structure observed experimentally becomes definitely the most favorable only if the vibrational contribution to the free energy is accounted for. Interaction with the gold surf…