Syntheses And Properties Of Extended Heterocyclic Aromatic Semiconductors Having Metal Coordination Sites

Linear aromatic heterocyclic semi-conducting compounds bearing delocalized π-systems, versatile donor-acceptor (D-A) hybrid spacers and certain coordination sites are expected to be valuable advanced functional materials on the applications of organic and polymeric light-emitting devices, field-effect transistors, photoconductive materials and photovoltaic solar cells. The photoelectric properties of these metal-containing semi-conducting compounds can be improved significantly by changing the central metal ions and by increasing the dimensionality of π-conjugated systems and so on. Therefore, it is highly important to design and synthesize novel organic semiconductors with the readily-tailored optical, electrical and magnetic properties. In summary, the thesis consists of three sections as follows:Chapter1A family of novel linear1,10-phenanthroline-based (A-D-A-D-A) heterocyclic aromatic fluorescence compounds having N-containing imidazole and pyridine tails with effective π-conjugated systems, prepared by the combination of carbon-carbon (C-C) bond and carbon-nitrogen (C-N) bond cross-coupling reactions, has been firstly described herein. They have molecular lengths more than2.30nm in the cases of L4, L6, L9, various D-A spacers and certain N-coordination sites (phen, imidazole and pyridine). X-ray single-crystal structures of ten compounds reveal a variety of trans and cis configurations with different dihedral angles between adjacent aromatic heterocycles. Synthetic, computational and spectral studies have been made to reveal the differences between cross-coupling approaches on the C-C bond and C-N bond formation as well as band gaps and energy levels, optical and electrochemical properties for related compounds. The influences of introducing aβ-methyl group to the thiophene ring on reaction activity, solubility and conformation of related compounds have also been discussed. Further studies are being undertaken on the coordination chemistry of this family of linear heterocyclic aromatic fluorescence compounds as well as the dye-sensitized solar cells, field-effect transistor, light-emitting and photoresponsive properties of corresponding coordination complexes, nanowires, nanocomposite films and nanodevices.Chapter2Eight transition metal complexes of3,8-di(thiophen-2’,2"-yl)-1,10-phenanthroline (dtphen) and3,8-bis(3-methylthiophen-2-yl)-1,10-phenanthroline(bmphen), formulated as [Ni(dtphen)2(H2O)2]·(ClO4)2(1),[Zn(dtphen)2(H2O)]·(ClO4)2(2)[Cu(dtphen)2(H2O)]·(ClO4)2(3),[Cu(dtphen)(phen)2]·(ClO4)2(4)(phen1,10-phenanthroline),[Cd(bmphen)·(C10H14O4)]·(CH3OH)(5),[Co2(bmphen)2ˇ(C10H14O4)2]·(H2O)3(6), Ru(bmtphen)·(bpy)2·(PF6)2·(H2O)2(7),[Eu(bmphen)(DBM)3]2·(H2O)3(8) with different metal-to-ligand ratios, were synthesized and characterized herein. The X-ray single-crystal diffraction studies of1-8exhibit that different molecular configurations for the dtphen and bmphen ligand can be observed where the side thiophene rings adopt the trans/trans, trans/cis, trans/disorder and cis/cis conformations relative to the central1,10-phenanthroline unit in different compounds. Some complexes were characterized by uv-vis absorption and fluorescence emission spectra. The results show that complexes7and8have photoluminescence property. The polymers of complex8were an ideal starting material to electroplate as luminescent conducting metallopolymers for a wide range of light-emitting applications.Chapter3Two new linear and V-shaped thiophene-based ditriazole bridging ligands, i.e.2,5-di(1H-1,2,4-triazol-l-yl)thiophene (L19) and3,4-di(1H-1,2,4-triazol-l-yl)thiophene (L20), have been synthesized and characterized. They are used to prepare eleven transition-metal coordination polymeric frameworks (five for L19, six for L20) exhibiting abundant structural diversity, where distinct metal/ligand ratios (1:2,1:1and2:1) and dimensions (ID,2D and3D) have been observed because of the alterations of the coordination modes of central metal ions, the shape and conformation of ligands and the participancy of counterions. They are formulated as{[Co(L19)2(H2O)2](ClO4)2}n (9),{[Zn(L19)2(H2O)2](ClO4)2}n (10),{[Ni(L19)2(H2O)2](ClO4)2}n (11), [Ag(L19)(NO3)]n (12),[Cu(L19)(CN)]n (13),{[Co(L20)2(H2O)2](ClO4)2}n (14),{[Zn(L20)2(H2O)2](ClO4)2}n (15),{[Ni(L20)2(H2O)2](ClO4)2}n (16),[Cd(L20)2(NO3)2]n (17) and [Cu2(L2)(SCN)2]n (18),[Ag(L20)(NO3)]n (19). ID chains have been formed in the cases of12and14-17,19, while2D planes have been built in9-11. In contrast,3D networks have been constructed in13and18due to the further linkage of CN-and SCN-counterions. The most intriguing is that complex12and19exhibit extraordinarily enhanced solid-state conductivity to different extent (1.42×104and2.17×103times) compare with their ligand. The formation of Ag-N coordinative bonds and the configurational differences of L19and L20are believed to play important roles in facilitating the electron transportations between molecules, which are supported by Density Function Theory (DFT) calculations of their band gaps.