Self-Assembly of Patterned Monolayers with Nanometer Features:  Molecular Selection Based on Dipole Interactions and Chain Length

Abstract

Patterned cocrystal monolayers self-assemble on HOPG in contact with solutions containing complementary pairs of 1,5-chain-substituted anthracene derivatives. Monolayer unit cells containing three or four molecules and spanning 9-11 nm are generated. The monolayers consist of alternating aromatic and aliphatic columns. The designs and dimensions of the cocrystal patterns (unit cells) are determined by (i) the preferred packing alignment of identical length side chains, (ii) the selectivity of each side chain for neighboring chains, (iii) the identities of the two side chains on each anthracene, and (iv) the 2D-chirality of 1,5-substituted anthracenes. The aliphatic columns form by interdigitation of identical length side chains arrayed in an antiparallel alignment, with the nth heavy atom of one side chain in registration with the (omega+2-n)th heavy atom of two adjacent chains ((omega <--> 2) packing). Adjacent side chains are attached, alternately, to anthracenes in one of the two flanking aromatic columns. The preference for (omega <--> 2) packing optimizes side-chain van der Waals interactions. The composition and fidelity of patterning in the cocrystal monolayers requires an additional source of "molecular recognition" in addition to side-chain length. Dipolar interactions, both attractive and repulsive, between ether groups in neighboring, (omega <--> 2) packed side chains, constitute a second recognition element needed for cocrystal self-assembly.

Self-assembly of zwitterionic molecules on a Au(232321) surface at low temperature

“…Therefore, the aliphatic part of MSPS is not visible by STM [33,34]. Based on these results, a model of adsorption can be proposed in which MSPS are adsorbed in a ''scorpion shape" with their p-skeleton parallel to the surface and the aliphatic chain pointing out of the plane, as described in Fig.…”

Self-assembly of strongly dipolar molecules on metal surfaces

“…Various examples can be found in published studies of organics under ambient atmospheric conditions, 1 at the liquid-solid interface 2 and under ultrahigh vacuum conditions, [3][4][5][6][7][8] with the molecular dipole aligned perpendicular to the surface 9 or within the surface plane, 3,4 and for various molecule sizes ranging from small molecules such as quinonoid zwitterions 3 and styrenes 4 to larger ones such as anthracene. 10 In reviewing those reported assemblies of dipolar molecules, it becomes evident that most of them do a) Electronic mail: ezurek@buffalo.edu b) Electronic mail: aenders2@unl.edu not correspond to a configuration of lowest electrostatic energy. Instead, molecules of similar dipole moment can repel each other on one surface 9 and attract each other on another.…”

Selective Formation of Bi‐Component Arrays Through H‐Bonding of Multivalent Molecular Modules

“…To this end it is therefore vital to use shape-persistent molecular modules dictating well-defined geometries to the supramolecular ensemble. Hitherto a large variety of interactions have been employed in order to hold together molecular modules forming targeted selfassembled mono-component architectures at surfaces including dipolar forces, [12][13][14][15][16][17] coordination bonds, [18][19][20][21][22][23][24] H-bonds, [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] and more recently covalent interactions. [40][41][42][43][44] Among the proposed approaches, the use of H-bonding [45] is very promising since this type of interaction features very high directionality and selectivity, along with a reversible character, providing access to a vast variety of sophisticated functional assemblies and materials barely accessible through conventional covalent synthesis.…”