Study On The Synthesis And Properties Of Biphenyl Triarylamine Hole Transport Materials

Biphenyl triarylamines have emerged as one of the most promising holetransport materials and play an important role for application in organicphotoconductive materials. The recent method for synthesis of triarylamines is using4,4′-diiodo-biphenyl to react with secondary arylamine and catalyzed by CuCl,1,10-phenanthroline. Biphenyl triarylamines are limited in industrial manufacture andapplication because of higher raw material costs of4,4′-diiodo-biphenyl.After screening of catalysts and ligands, we herein study on coupling reaction of4,4′-dibromo-biphenyl instead of4,4′-diiodo-biphenyl and diphenylamine by usingthe milder reaction conditions of the Buchwald-Hartwig catalytic system. We focuson the effects of reaction conditions of synthesis for N,N,N′,N′-tetraphenyl-benzidine,such as raw materials ratio, reaction time, amount of catalyst, acid binding agent,reaction temperature on yield of product have been investigated, and the optimalreaction conditions have been determined: the molar ratio of diphenylamine to4,4′-dibromo-biphenyl is2.5︰1, the amount of palladium acetate is0.05mmol, theamount of potassium tert-butoxide is20mmol, reflux at145℃for6h and the yield is78.89%. According to the optimum process above, we use the4,4′-dibromo-biphenyl,bromobenzene to react with diphenylamine,3-methyldiphenylamine,4-methyldiphenylamine,4,4′-dimethyldiphenylamine and β-naphthylphenylamine,respectively, for synthesis of two series of biphenyl triarylamines and triphenylamines N,N,N′,N′-tetraphenyl-benzidine(TPD), N,N′-bis(3-methylphenyl)benzidine(m-TPD), N,N′-bis(4-methylphenyl)benzidine(p-TPD), N,N,N′,N′-tetrakis(4-methylphenyl)benzidine(s-100), N,N’-bis(naphthalene-2-yl)-N,N’-bis(phenyl)benzidine (β-NPB), triphenylamine(TPA),3-methyl-N,N-diphenyl-benzenamine(m-TPA),4-methyl-N,N-diphenyl-benzenamine(p-TPA), bis(4-methylphenyl) phenylamine(dm-TPA), N,N-diphenylnaphthalen-2-amine(β-NPA), totally10kinds of compounds andthe yield is40.98%~79.89%. The novel method efficiently reduced the costs ofbiphenyl triarylamines as hole transport materials about20%. The syntheses of TPD,m-TPD, p-TPD and s-100have been amplified, the yield is73.98%,74.61%,71.51%and74.45%, respectively.The OPC photoelectric properties of biphenyl diamines have been tested, the E1/2 values of OPC with TPD, m-TPD, p-TPD, s-100and β-NPB are0.8lux·s,0.125lux·s,0.275lux·s,0.5lux·s,0.45lux·s. respectively, which confirms that excellentphotosensitive performance of biphenyl diammines as hole transport materials.The optimistic structure, dipole, Mulliken charge have been obtained onGaussian03by quantum chemical calculations. We find that the molecular plane canincrease the conjugate area which is good for hole transporting, and the hole mobilityincreases by the decrease of the dipole moment.