Molecular trapping in two-dimensional chiral organic Kagome nanoarchitectures composed of Baravelle spiral triangle enantiomers

The supramolecular self-assembly of a push-pull dye is investigated using scanning tunneling microscopy (STM) at the liquid-solid interface. The molecule has an indandione head, a bithiophene backbone and a triphenylamine-bithiophene moiety functionalized with two carboxylic acid groups as a tail. The STM images show that the molecules adopt an "L" shape on the surface and form chiral Baravelle spiral triangular trimers at low solution concentrations. The assembly of these triangular chiral trimers on the graphite surface results in the formation of two types of chiral Kagome nanoarchitectures. The Kagome-alpha structure is composed of only one trimer enantiomer, whereas the Kagome-beta structure results from the arrangement of two trimer enantiomers in a 1:1 ratio. These Kagome lattices are stabilized by intermolecular O-H center dot center dot center dot O hydrogen bonds between carboxylic acid groups. These observations reveal that the complex structure of the push-pull dye molecule leads to the formation of sophisticated two-dimensional chiral Kagome nanoarchitectures. The subsequent deposition of coronene molecules leads to the disappearance of the Kagome-beta structure, whereas the Kagome-alpha structure acts as the host template to trap the coronene molecules.