Main Chain Conjugated Polymers Containing Bipyridine Its Synthesis And Characterization Of Ruthenium Complexes

According to the requirements of polymeric solar cells,combining the advantages of dye sensitized solar cells and polymeric solar cells,two conjugated polymers containing ruthenium(Ru)-complexes and hole-transporting moieties in the main chain were designed and synthesized.Chemical structure of the prepared monomers and polymers were determined by measurements of melting point, ¹H-NMR and IR.Their molecular weight,thermal stability and light-absorption ability were characterized by GPC,TG and UV-vis,respectively.Firstly,the phosphonium salt of 2,2'-bipyridine and two monomers containing dialdehyde groups were synthesized.Then,two conjugated polymers containing bipyridine chelating ligand in the main chain(Pbpy-Ph and Pbpy-Cz) were synthesized by Wittig condensation polymerization.Afterwards,the conjugated polymers containing Ru-complex[Pbpy(Ru)-Ph and Pbpy(Ru)-Cz]were prepared by the reaction of Pbpy-Ph or Pbpy-Cz with Ru-complex.These two metal-complexes containing conjugated polymers have good solubility in common polar organic solvents such as THF,DMF and CHCl₃.The number molecular weights of Pbpy-Ph and Pbpy-Cz are 2.8×10³ and 1.2×10³ as measured by GPC,and the polydispersities are 1.13 and 1.24,respectively.Determined by TGA in N₂ atmosphere,the temperatures at 5%weight loss of Pbpy-Ph and Pbpy(Ru)-Ph are 371℃and 251℃respectively.Pbpy-Ph and Pbpy(Ru)-Ph are at 413℃and 208℃respectively.From the UV-vis aborption spectra,the polymer Pbpy-Ph shows absorption peaks centered at 415nm and 305nm due to theπ-π^* transitions of conjugated main chain and theπ-π^* transitions of the bipyridine units respectively.The absorptions of Pbpy-Cz are peaked at 373nm and 300nm.After the formation of metal complex,both polymers Pbpy(Ru)-Ph and Pbpy(Ru)-Cz exhibit a new low energy absorption band centerd at 585nm assignable to the metal-to-ligand charge transfer(MLCT),i.e.the d-π^* transition.From the photoluminescence spectra,the polymers Pbpy-Ph and Pbpy(Ru)-Ph exhibit strongπ^*-πemission bands centered at approximately 549 nm, and Pbpy-Cz�'�Pbpy(Ru)-Cz at about 440nm.However,after the formation of ruthenium complex,the emissions from the conjugated main chain in both polymers are quenched significantly,which is due to the presence of an energy transfer process from the main chain to the ruthemium complex with low-lying energy levels.Besides,a novel carbazole-based dialdehyde monomer containing a chelating ligand in the side chain was designed.This monomer was synthesized by Williamson reaction between(4'-methyl-2,2'-bipyridin-4-yl)methanol and 9-(6-bromohexyl)-9Hcarbazole -3,6-dicarbaldehyde.Chemical structure of all intermediates was conformed by ¹H-NMR.