Synthesis Of Substituted Polyaryls And Investigation Of Their Properties

The Suzuki-Miyaura cross-couplings can tolerate a large variety of functional groups and reaction conditions.However,the coupling reactions involving sterically hindered substrates,especially the ortho-ortho' substituted arylboronic acids,have known to be less successful due to steric hindrance or competitive hydrolytic deboronation.On the basis of the above presentation,we have found a fast and convenient method for Suzuki-Miyaura cross-coupling,and synthesize some polyaryls via Suzuki-Miyaura cross-coupling.There are mainly two sections in the thesis:In the first section,we found the high sterically hindered Suzuki-Miyaura could proceed very well in the presence of Pd(PPh₃)₄ as catalyst and KO'Bu as base in DME/^tBuOH within five minutes,and the yield can reach 40 to 94%. Multi-substituted polyaryls were synthesized successfully by the double couplings of sterically hindered arylboronic acids with ary1 dibromides under this reaction conditons.The thermal and optoelectronic properties were investigated by thermo-gravimetric analysis(TGA),ultraviolet-visible spectrophotometry(UV-vis), fluorimetry(FL) and cyclic voltammetry(CV).The structures of these compounds were optimized by the software of Gaussian 03,and the corresponding HOMO and LUMO energies were calculated at the DFT level of theory.The more conjugated coupounds 3e and 3f show higher melting point(＞234℃) better thermal stability (＞260℃) and good optoelectronic properties,their maximum absorptions show at 269 nm and 310 nm.The maximum emission wavelength of 3e can reach 386 nm.In the second section,we synthesize compounds 7a via the Suzuki-Miyaura cross-couplings in the presence of Pd(PPh₃)₄ as catalyst and K₂CO₃ as base and compounds 7b via the Suzuki-Miyaura cross-couplings in the presence of Pd₂(dba)₃ as catalyst,PPh₃ as ligand and KO'Bu as base.Both of 7a and 7b contain SMe,fluorene, phenyl in the structure.The optoelectronic properties were investigated by UV-vis,FL, CV and found that they have good optoelectronic properties.Their maximum absorptions show at 351 nm and 313 nm.The maximum emission wavelength of 7a can reach 410 nm.Meanwhile compounds 7a and 7b have high fluorescence quantum yield(59,65%respectively).So these fluorene derivatives have potential application in the organic light-emitting materials.