Two-Dimensional Self-Assembly of a Symmetry-Reduced Tricarboxylic Acid

Abstract

ABSTRACT:Investigations of the self-assembly of simple molecules at the solution/solid interface can provide useful insight into the general principles governing supramolecular chemistry in two dimensions. Here, we report on the assembly of 3,4′,5-biphenyl tricarboxylic acid (H 3 BHTC), a small hydrogen bonding unit related to the much-studied 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA), which we investigate using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. STM images show that H 3 BHTC assembles by itself into an offset zigzag chain structure that maximizes the surface molecular density in favor of maximizing the number density of strong cyclic hydrogen bonds between the carboxylic groups. The offset geometry creates "sticky" pores that promote solvent coadsorption. Adding coronene to the molecular solution produces a transformation to a high-symmetry host−guest lattice stabilized by a dimeric/trimeric hydrogen bonding motif similar to the TMA flower structure. Finally, we show that the H 3 BHTC lattice firmly immobilizes the guest coronene molecules, allowing for high-resolution imaging of the coronene structure.

Self-Assembled Monolayers of Oligophenylenecarboxylic Acids on Silver Formed at the Liquid–Solid Interface

“…On metal or graphite surfaces the focus has been on the formation of two dimensional molecular patterns of flat lying molecules through either hydrogen bonding or metal-organic coordination. [1][2][3][4][5][6][7][8][9][10][11][12] Investigations comprise both the ultrahigh vacuum (UHV) environment and the liquid/solid interface, the latter also including the electrochemical interface. [13][14][15][16][17] Compared to these activities only a few studies have focused on the formation of self-assembled monolayers * (SAMs) where, analogous to the extensively studied thiols and silanes [18][19] , molecules adopt an upright configuration with the carboxylate moiety acting as head group to anchor the molecule via coordination bonding.…”

Coronene Molecules in Hexagonal Pores of Tricarboxylic Acids: A Monte Carlo Study

“…The trimeric bonds are found either at higher molecular density 7,29-31 or when foreign molecules are incorporated in pores of a host molecules matrix. 28 In a former case they support the formation of flower phases of TMA molecules. In a latter case the guest (coronene molecule) stimulates the occurrence of hexagonal porous formations in BHTC system which must possess the trimeric bonds in order to build a symmetric structure with similar pore sizes.…”

“…The DFT calculations 28,31 show that the magnitude of e t is lower. This is the most probable reason why the C1 or C2 phases do not occur in the absence of coronene.…”

“…Note, that the ratio of trimeric interaction to the largest dimeric interaction in our DFT calculations was 0.86 (per molecule) in good accordance with previous results. 28 We approximately kept this ratio in our MC calculations. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 …”

“…The BHTC molecules demonstrate very interesting self-assemblies at the solid-liquid interface. 28 The dimeric H-bond interactions, analogous to those observed in honeycomb orderings of TMA and BTB molecules, play a crucial role in formation of ordered porous BHTC structures. Along with the dimeric bonds, a trimeric H-bonding motif similar to that found for TMA flower structure 7,29-31 is experimentally observed in BHTC system 28 when the coronene molecules are added.…”