Structure of and Competitive Adsorption in Alkyl Dicarbamate Two-Dimensional Crystals

Abstract

The potential for relatively minor structural changes to dramatically impact materials properties is one of the primary obstacles to achieving the rational design of functional materials. For example, having an odd versus an even number of carbons between functional groups in polymers can cause large variation in melting point and mechanical properties. This odd-even effect is especially pronounced in hydrogen-bonded polymers and oligomers. To shed light on the structural basis of this phenomenon, physisorbed monolayers and single crystals of alkyl dicarbamates were investigated by scanning tunneling microscopy and X-ray diffraction, respectively. The related two- and three-dimensional crystal structures both demonstrated a clear odd-even effect in packing geometry. The differing accommodation of intermolecular interactions between odd and even packing motifs was directly related to the melting point trends and further dissected through computation. In addition, these oligomers displayed unusual competitive adsorption behavior; the relative preference for adsorption of a smaller species from a binary solution was increased compared to alkanes. These results were explained in the context of hydrogen bond density effects that arise due to competition for a limited substrate surface area. This study provides a model for understanding oligourethane surface coatings and demonstrates the importance of molecular structure and hydrogen bonding in determining adsorption behavior.

Self-assembly of 2,6-naphthalenedicarboxylic acid and 4,4′-biphenyldicarboxylic acid on highly oriented pyrolytic graphite and Au(111) surfaces

“…Self-assembled monolayers (SAMs) of organic molecules on solid surfaces have been intensively studied in the past decade, due to their potential applications in molecular electronics, biosensors, materials science and host-guest chemistry [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Physisorbed SAMs, defined as SAMs formed by physisorbed molecules, have attracted particular interest recently, because these physisorbed molecules, directed by lateral non-covalent bonds, may form structure-controllable SAMs on single-crystal surfaces [1][2][3][4][5][6][7][8][9][10][11][12].…”

“…Physisorbed SAMs, defined as SAMs formed by physisorbed molecules, have attracted particular interest recently, because these physisorbed molecules, directed by lateral non-covalent bonds, may form structure-controllable SAMs on single-crystal surfaces [1][2][3][4][5][6][7][8][9][10][11][12]. Such kinds of technique for preparing structure-controllable SAMs are able to be used in assemblies of nano-entities and are considered to be the foundation of molecular electronics [1][2][3][4][5][6][7][9][10][11][12]. Up to the present, many physisorbed self-assemblies have been investigated by scanning tunneling microscopy (STM) [1][2][3][4][5][6][7][8][9][10][11][12], infrared spectroscopy (IR) [16][17][18], low energy electron diffraction (LEED), etc.…”

Insights into dynamic covalent chemistry at surfaces

“…7,8 Moreover, the principles beyond competitive adsorption when two or more building blocks are present at the interface, are well understood. 9,10 The above insights were obtained with the help of scanning tunneling microscopy (STM). With this scanning probe microscopy technique, it is possible to visualize very thin films, typically monolayers, at the interface between a liquid and an atomically flat conductive substrate such as HOPG, with submolecular resolution, and to reveal the structural properties of these films.…”

3-Oxapentane-1,5-diyl dicarbamate

“…Recently, self-assembled mono-layers of alkyl carbamates and alkyl dicarbamates have been investigated and characterized (Kim et al, 2003(Kim et al, , 2005a(Kim et al, , 2005b. Further, ligands with two amino moieties demonstrate versatile bonding modes to metal ions and readily form coordination polymers or supramolecular compounds (Xia et al, 2010(Xia et al, , 2011.…”