Versatile Role of Molecule–Surface Interactions for Monolayer Self-Assembly at Liquid–Solid Interfaces: Substrate-Induced Polymorphism, Thermodynamic Stability, and New Polymorphs

Abstract

Self-assembly of supramolecular monolayers at liquid–solid interfaces has matured into an established research field. Numerous studies unveiled crucial influences of solvent, solute concentration, and temperature on the kinetics and thermodynamics of monolayer formation and their specific role for structure selection. Yet, almost all experiments are carried out on highly inert graphite surfaces that are straightforward to prepare. However, the strong focus on graphite leaves the crucial impact of the underlying surface severely underexplored. Here, we show that passivation of Au(111) with a chemisorbed monolayer of iodine atoms renders it sufficiently inert for studies at liquid–solid interfaces, even at elevated temperatures. By using aromatic homologues of benzene tricarboxylic acids as a well-explored model system and by a one-to-one comparison to graphite, we unveil that molecule–surface interactions can cause substrate-induced polymorphism, crucially affect the supramolecular monolayer’s thermodynamic stability, or even result in the emergence of new polymorphs. These experiments underscore a decisive and specific thermodynamic influence of the underlying surface. We expect our study to stimulate further research on the surface influence on interfacial monolayers by employing this accessible and easy-to-prepare surface with the aim to establish a new lever for steering supramolecular self-assembly.

Kinetic versus thermodynamic polymorph stabilization of a tri-carboxylic acid derivative at the solid–liquid interface

“…Accordingly, we propose that SF is a thermodynamically more stable structure in nonanoic acid. This represents a remarkable exception to other tricarboxylic acids like TMA 1 and 1,3,5-tris[4-carboxy(1,10-biphenyl-4-yl)]benzene 2,14 that all exhibit solvent-induced polymorphism in fatty acid solvents, but with the more densely packed polymorphs emerging in the lower chain length fatty acid solvents. Yet, for unsubstituted TMA the solubility trend also goes in the opposite direction, i.e., the solubility monotonically decreases with the chain length of the fatty acid solvents.…”

“…This is remarkable because the binding energy per H-bond of 2-fold cyclic H-bonds is about 3.7 kJ mol −1 larger than that in 3-fold cyclic H-bonds. 14 That is, the phenylalanine substituents of l -BTA give not only rise to additional van der Waals interactions, but also facilitate additional intermolecular H-bonds that are not feasible in the self-assembly of unsubstituted TMA as highlighted in Fig. 1d.…”

“…Controlling the arrangement and binding of molecules in selfassembled monolayers is of primary importance as key properties depend on it. Molecular structure and symmetry, [1][2][3][4][5][6][7] chemical nature of the functional groups 8 and surface properties 3,[9][10][11][12][13][14] have been explored in this context at solidliquid and solid-vacuum interfaces. Self-assembly at solidliquid interfaces is particularly interesting as it offers additional parameters like the nature of the solvent 1,2,7,[15][16][17] and solute concentration, 12,18,19 for controlling the structure formation.…”

Influence of core size on self-assembled molecular networks composed of C3h-symmetric building blocks through hydrogen bonding interactions: structural features and chirality

“…1(b)). [22][23][24][25] TMA is the smallest such molecule that forms honeycomb (chicken-wire) and ower structures at the liquid/graphite interfaces, depending on its concentration and the identity of the solvent. 20,23 In the honeycomb structure, the TMA molecules are connected by complementary-type (R 2 2 (8)) hydrogen bonding interactions between the two carboxy groups, whereas in the ower structure, the TMA molecules are connected by both complementary-type (R 2 2 (8)) and cyclic-type (R 3 3 (12))…”

Steering On-Surface Reactions by Kinetic and Thermodynamic Strategies

“…Note that the establishment of a reversible bond formation is indispensable for efficient thermodynamic control, which has rarely been reported for the synthesis of covalently bonded nanostructures other than graphene on solid surfaces under ultrahigh vacuum conditions. However, the reversible bond formation conditions have been better established in experiments at near ambient pressures , as well as liquid–solid interfaces, , whereby the important role of the molecule–surface interactions has been addressed. These experiments would be the future directions for developing thermodynamic strategies to steer on-surface reactions.…”