| Since firstly synthesized in 1970s by Wudl et al., and stimulated by the discovery of the metallic conductivity of its 1:1 charge transfer complex with TCNQ, tetrathiafulvalene (TTF) has remained the most intensively studied heterocycle. Up to date, the design, synthesis and supramolecular assembly of new types of TTFs is one of the key gateways to achieve the organic functional materials, and the resulting materials have been applied in various organic electronic devices. Compared with the pristine TTF, its derivatives bearing aryl groups through the sulfur bridge are of particular interest, as they show (1) extended π-conjugated system and (2) large rotation/vibration freedom of the periperhal aryls around two C-S bonds. The later makes the TTFs to adopt various conformations according to the environmental variations, and consequently afford aboundant supramolecular structures which can be finely controlled by means of chemical and/or physical stimulations. In the present thesis, we report the design and sysnthesis of a series of sulfur-rich organic electron donor molecules and their supramolecular assembly with various electron acceptor molecules. The mechanism of the supramolecular assembly, the structures of the supramolecular system, and the physical properties of the supramolecular materials have also been disclosed. The main contents of this thesis are as followings:In Chapter 1, we made the brief introduction about the application of TTFs on supramolecular chemistry. We classified TTFs into three different types, that are linear, bent, and peripheral-subtituted ones. Owing to the variations on their molecular geometries, symmetries, rotation/vibrational freedoms, and electrochemical activities, these three types of TTFs show the different supramolecular assembly tendencies, and the supramolecular materials based on them show the different physical properties. The linear and bent TTFs are mostly employed to create organic conductors and magnetic conductors respectively, and the peripheral-substituted TTFs were applied in the molecular switches, sensors, data storage, etc. Finally, we have proposed the hypothesis of the present thesis, including molecule design, supramolecular assembly rationale, and the expected functionalities of the supramolecular materials.In Chapter 2, we reported the supramolecular assembly of aryl substituted TTFs with Keggin-type phosphomobdic acid (PMA). The supramolecular assembly was achieved by virtue of various intermolecular interactions to afford the "organic-inorganic hybrid" multifunctional materials. As a typical example, the thienylthio-substituted TTF (TT-TTF) has afforded the honeycomb supramolecular frameworks with PMA, which shows the one-dimensional nano-scale channels. The process of the supramolecular assembly and the molecular level structures has been thoroughly studied by UV-Vis spectroscopy, electrochemical investigation, dynamic light scattering, SEM, and X-ray single crystal diffraction analysis. On the basis of the above experimental results, we have proposed the mechanism on the supramolecular assembly, which belongs to the typical programmed assembly process as following: (1) the central C=C bond of the central TTF core is protonated to form (TTF1H)+; electron transfer between (TTF1H)+and TTF1 results in (TTF1)+· and (TTF1H)’, because TTF1 is more electron-rich than (TTF1H)+; recovery of TTF 1 from (TTF1H)’ under the oxidation of molecular oxygen, and the electrostatic interactions between (TTF1)+· and (PMonO40)3- afford an organic-inorganic hybrid nanocluster [(TTF1)+·]3[(PMo12O40)3-] as the building block; (2) the strong π-π interactions between (TTF1)+· result in the cluster-based two-dimensional honeycomb nanosheet; (3) the van der Waals forces between the nanosheets lead to the propagation along the third direction to form three-dimensional supramolecular framework possessing nano-sized channels.In Chapter 3, we reported the synthesis, structure, properties, and charge-transfer complexes of aryl-fused TTFs bearing EDO/EDT terminals. Due to intramolecular charge-transfer between the peripheral aryls and TTF core in the excited state, these TTFs there displays a weak absorption band at 400-500 nm. The EDO-terminated TTFs show the relatively lower oxidation waves than the EDT-terminated ones owing to the better electron-donating ability of EDO groups, and the first redox potentials of these TTFs are at around 0.5-0.7 V. The TTFs adopt the boat conformation as proved by the X-ray single crystal diffraction analyses. The morphologies of supramolecular assembled materials of these TTFs, that is the charge-transfer complexes with various electron acceptor molecules, are largely depended on the size, symmetry, and electrochemical activities of the acceptors. The large-sized counter components afforded bulk-crystalline complexes, whereas the small-sized components provided the nano-/micro-sized fibers.In Chapter 4, we reported the preparation, crystal structure and physical properties of the cation radical salts between bent TTF molecules and inorganic counter ions (FeCl4-, FeBr4-, PF6-, AsF6-, and ClO4-). The salts, which have the donor:anion ratio of 2:1, were obtained by the electrochemical oxidation of the bent molecules in the presence of (n-Bu4N)X (X= FeCl4-, FeBr4-, PF6-, AsF6-, and C1O4-). In the crystal structures of the salts, the donor molecules and counter ions formed segregated layers. The organic layers pave the conduction pathway, which makes these salts show the semiconducting behavior with moderate conductivities of 0.6-5.0 S cm-1. The strong spin exchange interactions between the organic cation radicals and the d-electrons on the counter ions are observed in the FeX4- (X= Cl, Br) salts, that is the so-called πc-d interaction. The corresponding salts are thus magnetic conductors to show the antiferromagnetic interactions of d-spins with Weiss temperature θ=-18.4 K. On the other hand, the salts with PF6-, AsF6-, and ClO4- as counter ions are Mott insulators as proved by the band structure calculation and magnetic measurement.In Chapter 5, we reported the supramolecular assembly of H10TTPR with various electron acceptor molecules, such as F4-TCNQ, PMA, and C60.We found that the size, shape, and symmetry of the acceptor showed significant influence on the structures of the resulting supramolecuar materials. The supramolecular assembly of H10TTPR with F4-TCNQ afforded the mixed columnar stacks of donor and acceptors, and the charge-transfer degree was estimated to be 0.3 according to the vibration frequency of CN group on F4-TCNQ. In the structure of ionic salt H10TTPR with PMA, the H10TTPR molecules locate in the void space formed by the PMA ions. In the case of C60 complex, H10TTPR served as the host to encapsulate C60. |
PDF Full Text Request