Investigation Of Supramolecular Coordination And Covalent Nanostructure Confined On Metal Surfaces

Organic molecules have been used as the building blocks for design and fabrication of functional materials/devices in future. In particular, understanding the process of organic material fabrication at a molecular level is highly desirable. This thesis focuses on the design and the fabrication of supramolecular nanostructures via coordination self-assembly, and the organic polymeric nanostructures through on-surface covalent Ullmann coupling as well. We used scanning tunneling microscopy(STM) to characterize the structures of these systems and to investigate the mechanisms of the self-assembly and polymerization processes at a single-molecule level.The results of this thesis consist of three parts as below:1. Supramolecular coordination self-assembly from nonplanar and planar organic building blocks. Two metal-organic coordination networks were respectively prepared by a planar molecular ligands(TPy P) and a nonplanar ligands(TPPM) with Fe atoms via pyridine-Fe coordination on Au(111). We can find on Au(111) square structures composed by TPy P and Fe atom that are stabilized by fourfold coordination. And a small amount of twofold and threefold coordination structure can be seen on the substrate. While TPPM molecules and Fe atoms form a honeycomb structure stabilized by threefold coordination. And we can find some bright dots in TPPM networks, which were attributed to the Fe atoms adsorbed at TPPM molecules nonplanar pyridine end groups. Similar to TPy P-Fe coordination structures, TPPM follows the general protocols of the self-assembly on metal surfaces, forming a two-dimensional network structure; On the other hand, because of its steric structure, TPPM remains some of its functional groups that retain their chemical functions coordination activity and allow the TPPM-Fe networks as a template to guide the formation of three-dimesional structures.2. Global control and local manipulation of two-dimensional Au-pyridyl supramolecular coordination networks. Different nanostructures can be found on different substrates, which means substrates can select and control supramolecular structures. We can obtain pure α1 phase on Au(111) surface after annealing the sample, because of interaction between molecular TPy PB and substrate. In addition, two types of coordination network formed by TPy PB and Au adatom, due to different concentration of Au adatom in distinct location. So we can use tip to increase the Au adatom concentration in small location, which will realize the precision control of self-assembly structure in a small location.3. Covalent nanostructures are controlled by metal substrates. We use STM to study the nano-structure which is formed by TBSF via surface Ullmann reaction on Au(110), Cu(111) and Cu(110) substrates. We found one dimension organometallic chains formed by molecular TBSF on Au(110) surface via STM. Because of Au(110) substrate has special conformation, the chains grow along <1 1? 0> direction on Au(110) surface. Organometallic chains would turn into short covalent chains with the rise of annealing temperature. Due to C-metal-C structure has high flexibility, organometallic chains’ length is much longer than covalent chains’ on Cu(111) substrate. While TPy PB were deposited on Cu(110) surface, we can not find 1D or 2D nanostructure on Cu(110) surface, due to the high reactivity.