Study On The Synthesis And Optical Characterization Of Triphenylamine Derivatives

Organic light-emitting-diodes (OLED) materials have attracted a great deal of attention, due to their promising applications in full-color, flat-panel displays as well as being a standpoint of scientific interest. Recently, pioneering work using the low molecular weight organic materials on electroluminescent (EL) devices has triggered extensive research and development of this field.Triphenylamine derivatives possess the properties of strong donated electron, high glass transition temperature, good solubility, low oxidation potential, high hole mobility and good forming film, therefore, they can be acted as attractive hole-transporting materials; what is more, triphenylamine derivatives can maintain uninterrupted conjugation which result in the emission wavelength in the blue green area. These compounds show interesting nonlinear optical properties, therefore, they can be used as emitting materials in OLED.The following works were completed:1. Synthesis of triphenylamine derivatives (1) Two intermediates4-nitrotriphenylamine (1a),4-aminotriphenylamine (1b) and four target compounds4-(benzenemethyamino)triphenylamine (lc),4-[(2-hydr-oxyl)-(benzenemethyamino)]triphenylamine (1d),4-[(2-nitro)-(benz-enemethyamino)]triphenylamine (1e),4-[tetrol-2-(benzenemethyamino)]-triphenylamine (1f) were synthesized through the Vilsmeyer reaction, nitration reaction, reduction reaction and condensation reaction using triphenylamine as raw material;(2) One intermediate4,4’-diformyl-triphenylamine (2a) and one target compound4,4’-dimethy-inferior-(a-naphthalene amino)triphenylamine (2b) were synthesized through the Vilsmeyer reaction, and reduction reaction using triphenylamine as raw material;(3) Four intermediates4-formyltriphenylamine (3a),4-[(trans)-(4-nitrostyryl)]triphenylamine (3b),4-formyl-4’-[(trans)-(4-nitrostyryl) triphenylamine (3c),4,4’-diformyl-4"-[(trans)-(4-nitrostyryl)]triphenylamine (3d) and seven target compounds4,4’-bis-[(trans)-(4-nitrostyryl)] triphenylamine(3e),4-[(trans)-(4-menthylstyryl)]-4’-[(trans)-(4-nitro-styryl)]triphenylamine(3f),4-[(trans)-(styryl)]-4’-[(trans)-(4-nitros-tyryl)]triphenylamine (3g),4-[(trans)-(a-vinyl-naphthalene)]-4’-[(trans)-(4-nitrostyryl)]triphenylamine (3h),4,4’-bis-[(trans)-(4-menthylstyryl)]-4"-[(trans)-(4-nitrostyryl)]triphenylamine (3i),4,4’-bis-[(trans)-(styryl)]-4"-[(trans)-(4-nitrostyryl)]triphenylamine (3j),4,4’-bis-[(trans)-(a-vinylnap-hthalene)]-4"-[(trans)-(4-nitrostyryl)]triphenylamine (3k) were synthesized through the Vilsmeier reaction and Wittig reation using triphenylamine as raw material. The structures of all intermediates and products were characterized by the IR,1H NMR and13C NMR spectrum. Synthesis experimental conditions of intermediates1b,3c, and3d were optimized to get the best synthesis conditions.2. The study of the optical properties of3e-3k:(1) Compared to the maximum absorption wavelength (300nm) of triphenylamine, the maximum absorption wavelength of3e-3k, which were between360-450nm in CH2Cl2, showed different degrees of red-shift. Among maximum absorption wavelength of3e-3k, the maximum absorption wavelength (449nm in CH2Cl2) of3e show the most obvious redshift. However, their UV-Vis spectrum occur blue shift with the solvent polarity increasing.(2) The fluorescence spectrum of3e-3k in different solvents was studied, the maximum emission wavelength was between450～632nm, which fit the requirements of OLED. The maximum emission wavelength of compound3e in THF was632nm, which belonged to red light area.(3) Optical band gap (Eg) of3e-3k was respectively2.14,2.14,2.16,1.98,2.47,2.16and2.11by calculating, obviously, lower than that of Alq3(3.21eV). The result shows that the compounds have higher hole-transporting ability, therefore,3e-3k can be served as good hole-transporting materials. Meanwhile, Stokes shift values calculated in different solvents were between5000～10000nm. Compared to Stokes shifts of other emitting materials, Stokes shifts of3e-3k were relatively small. The result shows that excited molecules lose smaller energy and have higher luminous efficiency. In a word, they will have a promising prospect as hole-transporting materials and emitting materials in OLED.