Palladium-catalyzed Synthesis Of C₃-symmetrictriaryl Triquinoline/Carbazole Derivatives

C3-symmetric conjugated aromatics are widely used in the fields of organic light-emitting diodes(OLEDs),photodiodes(PVD),organic field-effect transistors(OFETs),Organic solar cells(OSCs),sensors,liquid crystal materials,due to their symmetry and unique self-assembly capability.Compounds containing quinoline/acridine or carbazole have broad spectrum of biological activity and are widely found in biomedicine.Because of its structure easy to modify and having excellent photoelectric performance,Acridine,carbazole which are nitrogen-containing aromatic heterocyclic compounds have an important position in the development of organic optoelectronic functional materials.In this thesis,a series of compounds with C3-symmetric quinoline/acridine or carbazole moities were designed and synthesized.The spectroscopic properties,electrochemical properties and crystal structure of C3-symmetric quinoline/acridine compounds were also characterized.The first part is focused on the syntheses of 6,12,18-triaryldibenzo[b,j]quinoline[2,3-f][1,7]phenanthrolines.The reaction of 1,3,5-tribromobenzene with methyl anthranilate under typical Buchwald-Hartwig reaction conditions,followed by hydrolysis and POC13-promoted ring closure gave rise to the formation of key intermediate 6,12,18-trichlorobenzotriquinoline.Finally palladium-catalyzed Suzuki coupling was carried out with air-and water-stable catalyst Pd-132(II)and phosphine-ligand free to form fourteen target compounds.UV-Vis absorption spectroscopy,fluorescence emission spectroscopy and cyclic voltammetry(CV)is used to find that the compounds 38a,38i,381 and 38m have strong fluorescence emission peaks in the near ultraviolet region,and also has a certain emission intensity in the visible region,the band-gap energy is between 2.01 eV and 2.04 eV.The broad wavelength absorption range and the lower HOMO-LOMO energy gap lay the foundation for its potential applications in organic optoelectronic functional materials.The second part,we reported the synthesis of C3-symmetric 1,3,5-tris(3,6-Di-t-butyl-8-aryl-9H-carbazol-1-yl)benzenes with two different aryl groups on the 1,8-positions of carbazoles.It is noteworthy that the introduction of the same substituents at the 1,8-position of carbazole has been reported,but those with different aryl groups have not been reported.In this thesis,the following synthetic strategy was successfully conducted:3,6-Di-t-buty1-9H-carbazole was synthesized by Friedel-Crafts alkylation of carbazole with t-BuCl,which was site-selectively brominated at 1-position of carbazole with NBS to afford 1-bromo-3,6-Di-t-buty1-9H-carbazole;Another key intermediate 1,3,5-tris(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzene was obtained by coupling of 1,3,5-tribromobenzene with diboron pinacol ester,which reacted subsequently with 1-bromo-3,6-Di-t-buty1-9H-carbazole in the presence of palladium catalyst to form 1,3,5-tris(3,6-Di-t-buty1-9H-carbazole-1-yl)benzene.Another site-selective bromination on carbazoles were conducted with NBS,and followed by Suzuki coupling to finalize twenty target compounds.By using electrochemical measurements,the HOMO-LUMO energy gaps of 48c,48l,48n range from 1.8 to 2.0 eV.The investigations indicate that above compounds could be potentially useful as hole transport materials.