Lopatina Y. Self-organization of Organic Molecules on Atomically-Flat Surfaces.

The purpose of this work is to establish the regularities of self-assembly of organic molecules on atomically-flat surfaces. The main attention is focused on the structure of monolayer films depending on the internal structure of the molecules, functional groups and type of substrate. The structure of monolayers has been investigated by scanning tunneling microscopy (STM) at the liquid-solid interface. The atomically-flat surfaces of graphite and Au(111) were used as substrates. It has been established that n-hexacontane (C60H122) molecules form two types of smectic packing on the Au(111) surface - rectangular and oblique. The oblique packing corresponds to the metastable state, the rectangular – to the stable state. The transition from the metastable state to the stable state occurs with the formation of an intermediate nematic phase. STM revealed the effect of collective rearrangement of the ordered C60H122 monolayer on graphite. It has been suggested that the process starts with the growth of domain with different direction. Defects play a key role in this process. Clusters of the second layer C60H122 on graphite and Au (111) substrates were investigated. The influence of the substrate on the fragmentation of the second C60H122 layer is shown. Thus, the graphite substrate determines the orientation and size of clusters, while the Au (111) substrate determines orientation. Structure of self-assembled monolayers of alklyoxybenzene derivatives has been established on graphite. The transformation of 2-amino-1-dodecyloxy-5-nitrobenzene monolayer was observed. Rearrangement was followed by displacement of laterally extended molecular array. Chemisorbed monolayer films of alkanethiol derivatives SH-(CH2)n-R were investigated. It was found that 11-mercaptoundecanol (–OH) molecules form hexagonal structure. For the molecules with the carboxyl group (11-mercaptodecanoic acid) and dithiols (1,9-nonanedithiol, 1,4-butanedithiol) row structure was observed. The structural difference was explained by the association of molecules, interacting through terminal –COOH or –SH groups. It has been identified that the chemical activity of dithiol monolayers depends on the preparation technology, in particular on the duration of the Au(111) surface in the solution. The observed effect is explained by the formation of a disulfide (S-S) bond between adjacent molecules in the monolayer. The effect can be used in technologies based on the adsorption properties of organometallic interfaces. The monolayers of diamantane-thiols (C14H20-SH) on Au(111) were investigated by the STM for the first time. It was found that the structure and stability of the films depend on the position of SH-group. A polymorphism was revealed in the monolayer of diamantane-1-thiol. It has been established that the nature of adsorption (phys./chemisorption) in the monolayers of 3-arylpropanethiol-1 (3-naphthalene-1-yl-propane-1-thiol and 3-phenanthrene-9-yl-propane-1-thiol) on the Au(111) surface is determined by the size of the aromatic core of the molecule. Two types of packaging have been identified in the trioctyl-triazatriangulen monolayers on Au(111). Polymorphism results from the balance of the interactions of π-electronic systems of molecules and the substrate. It has been suggested that the formation of two structures is governed by a probability factor. A short-range order was found in monolayers of subphthalocyanine. The lack of long-range order is caused by incommensuration between monolayer and substrate. It has been found that the reconstructed surface of Au(111) exerts an orientation effect on the growth of the vacuum-evaporated rubrene films. The preferred direction for film growth is <112>.