STM observation of molecular chirality and alignment on solid surface

Two-dimensional adlayer of a helically shaped aromatic compound, hexathia[11]heterohelicene ([11]TH), which consists of fused five benzene rings and six thiophene rings, was prepared on Au(1 1 1), Au(1 1 0) and polycrystalline gold under UHV condition. LEED and STM were used for characterization of alignment, ordering and chirality of [11]TH on these An substrates. A [11]TH monolayer on Au(1 1 1) showed the presence of an adlayer lattice with six-fold symmetry, while [11]TH on Au(1 1 0) did align along (1 (1) over bar 0) direction, and [11]TH adsorbed on a step bunching area formed chiral sensitive arrays, being one-dimensionally aligned chains. These observations are discussed in terms of stereoselective interaction among [11]TH's, which is strongly affected by the surface structure of a substrate. (C) 2003 Elsevier Science B.V. All rights reserved.