Synthesis And Characterization Of Acenes And Sulfur-containing Heteroacenes Bridged Bimetallic Ruthenium Complexes

With the microminiaturization of electronic products, designing and developing electronic devices from molecular level has gradually become main research field for many researchers. Molecular wires, as one of the key components in molecular electronic circuits, are the theoretical and technical basis to carry out the micromation of electronic devices. Binuclear metal complexes consisting of conjugated bridge ligands and two redox centers, are widely used model as molecular wires, which were entitled as "organometallic molecular wires". When these complexes located in mixed-valence states, structure and properties of the bridge ligands can directly tune the degree of electronic communication between the two metal centers. Conversely, the degree of electronic transfer also indicates that if the bridge ligands could serve as potential molecular wires.Polycyclic aromatic hydrocarbons (PAH) and sulfur-containing heteroacenes have been widely applied in organic semiconductors because the rich electronic properties associated with their linear delocalized ?-system. However, there are few examples about using them as bridge Iiands in molecular wire models to investigate electronic coupling properties of binuclear or polynuclear metal complexes.With this in mind, by using "RuCl(CO)(PMe3)3-CH=CH-" or "(?2-dppe)(?5-C5Me5)Ru-C=C-as redox-active end groups and polycyclic aromatic hydrocarbons (PAH) or sulfur-containing heteroacenes units serve as bridge ligands, we have synthesized five series of binuclear ruthenium vinyl or alkyl complexes, and their electronic properties were studied by electrochemistry(CV and SWV), UV/vis/NIR and IR spectroelectrochemistry, electron paramagnanetic resonance (EPR), as well as the DFT calculations to investigate roundly the electronic coupling properties of these complexes, the main content of this dissertation is described as follows:1. Four bimetallic ruthenium vinyl complexes II-1-II-4have been designed and synthesized, in which two redox-active metal ends "[(PMe3)3(CO)Cl]Ru-CH=CH-" are attached to different positions (9,10-;1,5-;2,6-;1,8-) of anthracene. The target complexes have been characterized by NMR, elemental analyses, IR, UV-vis, fluorescence spectrum and X-ray crystal diffraction. Crystal structures indicated that complex II-3exhibits better coplanarity than complex II-1. Electrochemistry studies revealed that complexes II-1and II-4have stronger electronic coupling and higher mixed-valence state stability than that of complexes II-2and II-3. IR spectroelectrochemistry, EPR spectroscopy and electron spin density distribution calculation results all indicated that the anthracene vinyl group takes participate in the whole oxidation process, implying clear redox non-innocence ligand character. UV-vis-NIR spectroelectrochemistry associated with TDDFT calculations indicated that NIR absorptions of singly oxidized species [II-2]+~[II-4]+are mainly assigned to metal to ligand charge transfer (MLCT) transitions, and exhibited distinct hole transfer character. In addition, though complexes II-1and II-4have larger AE values, their coplanarity is poor, so complexes II-1and II-4are not propitious to the charge transfer. However, singly oxidized complex [II-3]+displayed the strongest NIR absorption bands and better coplanarity, which demonstrated that complex II-3has higher charge transfer ability and could serve as promising molecular wires.2. In order to maintaining the distance between redox-active centers, and investigating how the conjugation degree changes of bridge ligands in vertical direction affect the electronic coupling between the metal centers, we used1,4-benzene,1,4-naphthalene,1,4-anthracene and5,12-tetracene as bridge ligands respectively, designed and synthesized four bimetallic ruthenium vinyl complexes III-1-III-4. All of these compounds were characterized by NMR, elemental analyses, IR spectrum and X-ray crystal diffraction. Electrochemistry studies indicated that, with the increasing of conjugation degree of bridge ligands in vertical direction, electronic interactions between two metals and the stability of mixed-valence states gradually fall down. IR spectroelectrochemistry, EPR spectroscopy and HOMO composition from DFT calculations all revealed that bridge ligands have main contribution to the oxidation processes of these complexes. In addition, the v(CO) changes upon oxidation revealed that the increasing of conjugation degree of bridge ligands in vertical direction does not favor the charge delocalization. UV-vis-NIR spectroelectrochemistry results displayed that monocation [III-4]+has no absorptions in NIR region, which may be contributable to poor coplanarity in III-4. NIR absorptions of singly oxidized species [III-2]+and [III-3]+can be deconvoluted into three and five Gaussian-shaped sub-bands, respectively. Combined with TDDFT calculation results, these sub-bands can mainly come from MLCT transition absorptions, which features redox non-innocence ligand character of these complexes.3. Utilizing four benzodithiophene somer as bridge gands, and "(?2-dppe)(?5-C5Me5)RuC=C-" as metal terminal group, we designed and synthesized four bimetallic ruthenium alkyl complexes IV-IV-4. All of this compounds were characterized by NMR, elemental analyses, IR spectrum, and molecular structures of complexes IV-1, IV-2and IV-3were further confirmed by X-ray crystal diffraction. Electrochemical results indicated that linear benzo[1,2-b;4,5-b']dithiophene bridged bimetal complex IV-1features the strongest electronic communication and highest mixed-valence state stability. IR Spectroelectrochemical studies revealed that bridge ligands have dominative contributions in the oxidation processes, and feature redox non-innocence ligands character, which were further supported by spin density distribution calculations and EPR experiment results; Besides, according to v (C=C) changes, complex IV-1features the higher charge delocalization degree. UV-vis-NIR spectroelectrochemical studies as well as TDDFT calculations results demonstrated that MLCT transitions have larger contributions to intense NIR absorptions of [IV-1|+, the intense MLCT transition absorptions can illuminate that benzo[1,2-b;4,5-b']dithiophene can serve as better hole transfer materials and its derivatives have potential application in electronic devices.4. Take advantage of benzo[1,2-b;4,5-b']dithiophene with the best charge delocalization ability as bridge ligand to link different redox active terminus "(?2-dppe)(?5-C5Me5)FeC=C-" and=CH-", bimetallic iron alkyl and ruthenium vinyl complexes V-1and V-2were prepared; Besides, Selecting three bridge ligands derivated from benzo[1,2-b;4,5-b']dithiophene and the same metal terminus "(?2-dppe)(?5-C5Me5)RuC=C-", three bimetallic ruthenium alkyl complexes V-3-V-5were designed and synthesized. The target complexes have been structurally characterized by NMR and elemental analyses. Electrochemical studies revealed that metal terminus and bridge ligands both affected half-wave potential and mixed-valence state stability, half-wave potential with complex of Fe redox-active center is lower than that of complex of Ru center; Electron-donating ligands are favorable to increase the electronic interaction between metals and stabilizing mixed-valence states. IR spectroelectrochemical studies indicated that bridge ligands take participate in the oxidation process of these complexes, the phenomenon become more obvious in bimetallic ruthenium vinyl complex V-2and complexes V-4and V-5bridged by electron-donating ligands, aforementioned results were further supported by spin density distribution calculations. In addition, benzo[1,2-b;4,5-b']dithiophene as bridge ligand with different metal terminus all realized the better charge delocalization; electron-donating ligands can enhance the charge delocalization. UV-vis-NIR spectroelectrochemistry experiments and TDDFT calculation results shown that the NIR absorptions of singly oxidized species [V-1]+,[V-2],[V-4] and [V-5] can be assigned mainly to MLCT transitions.5. Six bimetallic ruthenium alkyl complexes V1-1~V1-6, in which oligothiophenes and thienoacenes with rich electronic properties serve as bridge ligands, have been designed and synthesized. The target compounds were characterized by NMR, elemental analyses, IR spectrum, and molecular structures of complexes V1-3, V1-5and V1-6were further confirmed by X-ray crystal diffraction. Electrochemical studies indicated that interactions between two metal centers and stabilities of mixed-valence states are highly dependent on the length and conjugation degree of bridge ligands, thienoacenes with better conjugation as bridge ligands which are propitious to interaction between two metals and stabilizing mixed-valence states. IR spectroelectrochemistry results revealed that singly oxidized species [VI-1]+-[VI-6]+all exhibit bridge-localized ground state characters, this conclusion was further proved by spin density distribution calculations and EPR spectroscopy experiments. According to changes of v (C=C), degree of charge delocalization of monocations gradually reduced with the elongation of bridge ligands. UV-vis-NIR spectroelectrochemistry as well as DFT (TDDFT) calculations results found that NIR absorptions of mono-cations species [VI-1]+~[VI-6]+can be contributable to MLCT transitions which are dominated by the bridging ligands. The absorption bands in visible-light region can be tentatively assigned to vibrationally structured aromatic radical bands, which both implied redox non-innocent character of the bridging ligands, the character can be result from HOMO-inducted hole transport. Therefore, above results all indicated that thienoacenes with rich electronics and coplanarity have strong charge delocalization abilities, and can serve as long-range charge transport materials.