Molecular Self-Assembly of Enantiopure Heptahelicene-2-Carboxylic Acid on Calcite (101̅4)

• Published in: Journal of physical chemistry. C Vol. 116; no. 7; pp. 4637 - 4641
• Main Authors: Hauke, Christopher M, Rahe, Philipp, Nimmrich, Markus, Schütte, Jens, Kittelmann, Markus, Stará, Irena G, Starý, Ivo, Rybáček, Jiří, Kühnle, Angelika
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 23-02-2012
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Atomic force microscopy; Molecular form; Molecular structure; Carboxylic acids; Calcite; Racemates; Self-assembly; Molecular assembly; Chirality; Enantiomer; Superstructure; Cleavage; Ultrahigh vacuum; Non contact measurement
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp2102258

Chirality can have a decisive influence on the molecular structure formation upon self-assembly on surfaces. In this paper, we study the structures formed by enantiopure (M)-heptahelicene-2-carboxylic acid ((M)-[7]HCA) on the calcite (101̅4) cleavage plane under ultrahigh vacuum conditions. Previous noncontact atomic force microscopy studies have revealed that the racemic mixture of (M)-[7]HCA and (P)-[7]HCA (1:1) self-assembles into well-defined molecular double rows that are oriented along the calcite [011̅0] direction. Here, we investigate the enantiopure (M)-[7]HCA compound, resulting in distinctly different molecular structures upon deposition onto calcite (101̅4). In sharp contrast to the racemate, the (M)-[7]HCA enantiomer forms molecular islands with a (2 × 3) superstructure. Comparison of the results presented here for the enantiopure compound with the results previously obtained from the racemate indicates that heterochiral recognition is responsible for the formation of the unidirectional double row structures formed by the racemate.