| Organic molecules physical adsorb at liquid/solid interface, forming different assemblies, which are dependent on molecular structures, molecule-molecule interaction, molecule-substrate interaction. In the field of molecular assemblies, the modulation and controlof the 2D structure is more important, and bigger challenge. In the self-assembly process, the hydrogen-bond between the molecules is a dominant factor in the formation of 2D nanostructure because it is much stronger than the van der Waals interaction between the substrate and molecules.1) In this dissertation, we attempted to investigate the two-component assemblies of N,N'-dialkyl-substituted quinacridone derivatives with dicarboxylic acids by STM and focused our discussion on whether the supramolecular organization could be modulated by coadsorption of dicarboxylic acids bearing different lengths of alkyl chains. We have demonstrated that the mixture of the quinacridone derivatives and bifunctional acid can form uniform adlayers and the introduction of bifucntional acid can control the 2D structures formed by quinacridone derivatives. No matter how bifunctional acids of long or short alkyl chains are used, the host and guest molecules can adjust their conformations to adapt to each other simultaneously forming energy-favored 2D assemblies. In all the cases investigated, we have observed that the coadsorption of TmQA-C16 and pentadecanedioic acid regularly arrange on the surface with two different conformations. This study provides a new approach for modulating the patterned structure of quinacridone derivatives with strong light-emitting properties.2) We studied the 2D assemblies of the double-substituted series of quinacridone derivatives by STM and attempted to modulate their 2D assemblies by co-adsorbing monofunctional acid and dicarboxylic acid, respectively. Different from the quinacridone derivatives reported, we have demonstrated that a series of double-substituted quinacridone derivatives take contractive conformation for its 2D assemblies on HOPG. Co-adsorption with the monofunctional acid stearic acid by hydrogen bond, D(TFM)QA-C22, bearing two smaller substituted groups of trifluoromethyl takes an extended conformation, while DTBuQA-C22, bearing two larger substituted groups of tert-butyl, still takes a contractive conformation. In the case of co-adsorption with bifunctional dicarboxylic acid, both D(TFM)QA-C22 and DTBUQA-C22 take extended conformations. The larger the double-substituted group, the more quinacridone derivatives tend to take contractive conformation. Clearly, bifunctional dicarboxylic acid can modulate the 2D assemblies of quinacridone derivatives in a more efficient and controlled manner than monofunctional fatty acid. We hope our result can be helpful in understanding the 2D assemblies of quinacridone derivatives and provide valuable information for the design and control of 2D supramolecular assemblies of quinacridone derivatives.3) Among the research of 2D supramolecular assemblies of organic molecule at the liquid/solid interface, halogen bonding is seldom mentioned. Meantime, there is no report on imaging analytical methods such as TEM, SEM, AFM, STM visualizing the structure of halogen bonding directly. For the first time we report the 2D assemblies structure based on the halogen bonding, and observe the subtle structure of the 2D assemblies driven by halogen bonding though STM. We select a pair of building blocks, N-(2,3,5,6-tetrafluoro-4-iodophenyl)hexadecylamine as an acceptor and 1-dodecyl-imidazole as a donor. The result indicate the forming of halogen bonding can enhance the interaction between organic molecules and HOPG substrate, benefit to the forming of its 2D supramolecular assemblies structure. Moreover, this line of research can enrich the family of low-dimensional supramolecular assemblies by introducing another driving force, such as halogen bonds.
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