Tuning the self-assembly of 5-amino [6]helicene on solid surfaces

HUGO ASCOLANI; MAARTEN VAN DER MEIJDEN; LUCILA CRISTINA; J. ESTEBAN GAYONE; RICHARD KELLOGG; JAVIER FUHR; MAGALI LINGENFELDER

Congreso; The International Chemical Congress of Pacific Basin Societies 2015; 2015

Over the past 15 years, scanning tunneling microscopy (STM) studies have shown that chiral expression can be explored in great detail for molecules adsorbed on metal surfaces. Particularly interesting model systems are helicenes, compounds with ortho-condensed aromatic rings presenting axial chirality. They have a fascinating chemistry due to their unique screw shaped pi conjugated system. Here we report the investigation of 5-amino[6]helicene (AH) on solid surfaces under ultra-high vacuum (UHV) by a combination of STM and density functional theory (DFT) calculations. AH represents an interesting model system for the study of the interplay of van der Waals (vdW) and H bonding groups and its influence on the chiral footprint of the enantiopure adsorbates on a solid surface. We compare the self-assembly on Cu (100) and Au(111). The chief difference between the two analysed surfaces is found in the origin of the molecule-surface interaction. While the C6 rings-surface interaction dominates in the case of Cu(100), the amino-surface interaction is crucial on Au(111). In both cases, it is significant that the amino group does not induce polar interactions via hydrogen bonding but rather that the maximization of vdW interactions drives the self-assembly. Further studies of (MP)AH on Cu(100), Au(111) and SnCu(100) indicate that vdW interactions also determine the assembly of the racemate.[Reference: H. Ascolani, M. W. Meijden, L. J. Cristina, J. E. Gayone, R. M.Kellogg, J. D. Fuhr, and M. Lingenfelder, Chem. Commun.50,13907 (2014)].