Cooperativity in the Self‐Assembly of the Guanine Nucleobase into Quartet and Ribbon Structures on Surfaces

The guanine nucleobase can self‐assemble into tetrameric or ribbon structures on surfaces or in solution. The origin for the occurrence of different aggregation patterns has not yet been investigated. Herein, a quantum chemical study on the different self‐assembled structures of guanine and xanthine by using dispersion‐corrected DFT is presented. Theoretical investigations can be used to explain, from an electronic point of view, the differences between the experimental findings. With quantitative Kohn–Sham molecular orbital theory and the accompanying energy decomposition analysis, the hydrogen‐bonding mechanism within the guanine ribbons can be disclosed and the preferred self‐assembled structures under different experimental conditions can be explained. An important role of the σ‐electronic system in the guanine self‐assembled structures is revealed as the main factor for the switch between different arrangements on surfaces and in crystals. Coming to an arrangement: High‐level density functional analyses explain the preference of the guanine nucleobase for ribbon structures over the quartet arrangement (see figure). Enhancement in the hydrogen bonds, which originates mainly from charge separation in the σ electronic system, favors one particular ribbon structure.