Synthesis And Characterization Of(Benzo-)Thiophthene Bridged Complexes Containing Different Active Terminal Group

As size of devices and components becomes increasingly smaller,research based on molecular devices has been a widely shared concern.Molecular wire is a key part of molecular device,a bridge connecting molecular device and outside world,with advantages of small size,diversity,adjustable performance and etc.,is expected to be used for a broad of applications and has become a new research area.Metal complex formed by using conjugated organic molecule as bridging ligand to connect redox-active metal center is an important model of "molecule wire",i.e.the most common "metal organic molecule wire".Compounds using arylamine unit as redox-active end group can also realize electron transfer through bridging ligand and thus becomes an indispensible object for the research of "organic molecule wire".However,the discussion will be made in the following sections based on classic metal complex for ease of presentation.It is widely reported that electron transfer between active centers is somehow affected by the structure and property of bridging ligand when organic molecule wire is in a mixed-valence state;meanwhile,electron interaction force between active centers of mixed valence system is also the basis for finding the possibility of using bridging ligand as molecule wire.Based on the above,selection of an appropriate bridging ligand is the key to molecule wire research.Furthermore,in recent years,thiophene conjugated compound has been widely used in organic semiconductor research because it is stable and electron-rich.This thesis intends to use(benzo-)thiophthene as bridging ligand to coordinate with metal center or connect with triarylamine end group to design and synthesize a series of new organic molecule wire for studying electron transfer capacity between two redox-active centers.Characterization of target compounds was analyzed by NMR,X-ray single crystal diffraction,electrochemistry(circular and square wave voltammetry),UV-visible-near-infrared and infrared spectrum electrochemistry to study electron coupling inside compound molecules.Specific research has been conducted as follows:1.Cis-and trans-thieno[3,2-b]thiophene bridged bimetal ruthenium acetylene complexes 2-1 and 2-2 and bis(triphenylamine)compounds 2-3 and 2-4 were designed and synthesized.On the basis of comparison of electrochemical and spectroelectrochemical properties of cis-and trans-thieno[3,2-b]thiophene bridged bimetal ruthenium acetylene complexes 2-1 and 2-2,electrochemistry studies show that in terms of the intramolecular electron interaction,cis-configuration complex 2-1 is stronger and has higher mixed-valence state stability than trans-configuration complex 2-2.IR spectrum reflects the redox non-innocence characteristics of both during oxidation process.Change of complexes 2-1 and 2-2 which are oxidized in UV-Vis-NIR further confirms electrochemical experiment results.By comparison of electrochemical and spectroelectrochemical properties of thieno[3,2-b]thiophene bridged bis(triphenylamine)compounds 2-3 and 2-4,we may discover that DE value and Kc value of the two are smaller than corresponding ruthenium compounds.This may be because the benzene ring unit of arylamine and thieno[3,2-b]thiophene unit are not coplanar.Moreover,change of compounds 2-3 and 2-4 which are oxidized in UV-Vis-NIR further confirms the fact that bridging ligand takes part in the oxidation process.2.Trimetal ruthenium acetylene and iron-acetylene complexes 3-1 and 3-2 was synthesized by using benzo[1,2-b:3,4-b0:5,6-b00]trithiophene(BTT)as bridging ligand“(?2-dppe)(?5-C5Me5)Ru-C?C—)" or "(?2-dppe)(?5-C5Me5)Fe-C?C—" as metal end group.According to the analysis of electrochemical test results,there is a great difference in the oxidation potential between compounds 3-1 and 3-2 with different end groups.In addition,the oxidation potential difference for the first two steps of compound 3-1 is larger than compound 3-2,indicating that stability of the oxidation state is relatively stronger.In a word,when the bridging and ancillary ligands are the same,the difference of active metal center has much effect on electronic transmission.According to the analysis of IR spectroelectrochemistry test results,during a sequence of oxidation process of complexes 3-1 and 3-2,change of the absorption intensity and position of C?C bond linked with bridging ligand shows that bridging ligand involves in oxidation,which displays its redox non-innocence features.Based on the analysis of UV-Vis-NIR spectroelectrochemistry test results,change of the absorption band of complexes 3-1 and 3-2 in the oxidation process indicates that bridging ligand gets involved in the process.