G. Moessner

Molecular organization of azobenzene derivatives at the liquid/graphite interface observed with scanning tunneling microscopy

Physisorbed monolayers of azobenzene derivatives were studied with a scanning tunneling microscope at the liquid/graphite interface. Three different compounds, namely, 4,4′-di(dodecyloxy) azobenzene (C12(AZO)C12), 5-[ω-(4′-dodecyloxy-4-azobenzene-oxy)dodecyloxy] isophthalic acid (C12(AZO)C12ISA), and 4,4′-bis(ω-[3,5-bis(carboxylato) phenyl-1-oxy] dodecyloxy) azobenzene (ISAC12(AZO)C12ISA) have been investigated. In all cases monolayers could be observed with submolecular resolution at the liquid/graphite interface, allowing one to identify the azobenzene, as well as the other parts of the molecules. For each monolayer structure a molecular model could be composed with a good correspondence to the experimental data. Differences in the observed monolayer structures could be related to the chemical structure of the investigated compounds. The introduction of an isophthalic acid (ISA) headgroup has a profound influence on the monolayer structure because of its capability of hydrogen bond formation with other ...

Self-assembly of 5-alkoxyisophthalic acids: alkyl chain length dependence for the formation of channel-type and sheet-type structures

The effect of alkyl substituants at the C(5) position of isophthalic acid in the self-assembly of the title compounds is discussed with the aid of seven new crystal structures. The formation of channel-type (6 ⩽ n < 12) and sheet-type (n ⩾ 12) structures from 5-alkoxyisophthalic acids (CnISAs) in the crystal lattice is described. One of the reasons proposed for the formation of the cyclic and sheet-type structures observed in the crystal lattice from the title compound is the length of the alkyl chain (n = number of carbon atoms in the alkyl chain). The tolerance limit of the channel-type crystal lattice towards polar functional groups is also discussed. The cyclic structures that are observed may also be converted into a ribbon-type form under appropriate conditions.