Odd/Even Effect in Self-Assembly of Chiral Molecules at the Liquid−Solid Interface:  An STM Investigation of Coadsorbate Control of Self-Assembly

Abstract

Manipulation of the self-assembly of chiral 2-bromohexadecanoic acid by templates composed of coadsorbed achiral molecules has been investigated at the liquid-solid interface using scanning tunneling microscopy (STM). The template formed by the odd-numbered saturated fatty acid heptadecanoic acid induces coadsorption of R-2-bromo-hexadecanoic acid and S-2-bromo-hexadecanoic acid within a single domain. Specifically, heptadecanoic acid effects an intra-lamellar alternation of R and S-2-bromo-hexadecanoic acid molecules, which is further confirmed by studies of heptadecanoic acid with pure R-2-bromo-hexadecanoic acid. Templates formed by even-numbered acids such as hexadecanoic acid induce the segregation of R-and S-2-bromohexadecanoic acid into separate (R or S) domains.

Vapor pressures of 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with long alkyl chains

“…33,34,43 Analogous to the observed in the crystal packing for other alkyl series, the orientation of the terminal groups is determinant for the molecular interpretation of the even-odd effect. 62,63 This effect is expected to disappear or be very small in isotropic systems. In fact the appearance of the evenodd effect in ionic liquids is highly relevant as a support for the existence of nanostructuration in the liquid phase as well as an indication that the nanostructuration becomes more significant with the alkyl chain size increase.…”

Asymmetry Induction by Cooperative Intermolecular Hydrogen Bonds in Surface‐Anchored Layers of Achiral Molecules

“…Moreover, producing surfaces with chiral signature is of practical interest due to their selective response when interacting with adsorbed species, whence their stereochemical properties can be exploited for enantio-selective heterogeneous catalysis and ultra-sensitive molecular detection. Several methodologies are exploited for the preparation of chiral surfaces: Using their intrinsic crystallographic symmetry (such as high-index chiral metal surfaces [1][2][3] ); adsorbing chiral [4][5][6][7][8][9][10][11][12] or pro-chiral (two-dimensionally chiral) [13][14][15][16][17][18][19] molecular species, which become chiral by mirror-symmetry breaking upon 2D confinement on a substrate, and by the respective combinations-for example, by molecular asymmetric restructuring of the substrate, [20,21] by coadsorption of achiral and chiral species, [12,22] or by using the electrodeposition technique in the presence of chiral molecular ions. [23] Moreover, chirality can be achieved at the supramolecular level by the assembly of either achiral, prochiral or chiral molecular building blocks in architectures implying symmetry breaking.…”

Self-Assembly of Small Polycyclic Aromatic Hydrocarbons on Graphite: A Combined Scanning Tunneling Microscopy and Theoretical Approach

“…12 The versatility of STM is limited only by its inability to distinguish different chemical groups or atoms; however related techniques such as scanning tunneling spectroscopy and inelastic electron tunneling spectroscopy can in principle provide unique electronic or vibrational signatures for surface atoms and adsorbate functional groups. 12,[22][23][24][25][26][27][28][29][30] Numerous STM studies have focused on understanding the spontaneous self-assembly of molecules on surfaces, including the physisorbed monolayers formed at the liquid-graphite interface 1,[3][4][5][8][9][10]18,21,28,[31][32][33][34][35][36][37][38][39][40][41] and the vacuum-graphite interface. [23][24][25][42][43][44][45][46][47][48][49][50][51][52] Information about the factors that promote twodimensional self-assembly, such as van der Waals forces, electrostatic forces, and hydrogen-bonded...…”