Synthesis And Optical Characteristics Of Triphenylamine Schiff Bases Compounds

Organic light-emitting diodes (OLEDs) have attractedmuch attention due to their potential application in flatpanel lightings and flat panel displays because of their highefficiency, fast response time, and wide viewing angle.Small molecules are semi crystalline or crystalline materials with high aqueous solubility,so they can be used as emitting materrials in OLED.Triphenylamine and its derivatives have received considerableat-tention in the field as they are an excellent hole transport materialthat constitutes one of the essential layers of the OLEDdevice.Very good performance of triphenylamine derivatives as HTM isattributed to relatively high hole mobility and low ionizationpotentials. It can be used as an emitting materials in OLED, because triphenylamine derivatives with good fluorescent properties.In this paper, a series of conjugated compouds containing triphenylamine were designed and synthesized. And the spectral property of partly synthesized compouds was explored preliminarily.1. Synthesis of eleven intermediates and ten target compounds:(1) pho-sphonium salts were synthesized for wittig reaction:benzyltriphenylphosp-honium chloride (1a),(4-nitrobenzyl) triphenylphosphonium chloride (1b), (4-methylbenzyl) triphenylphosphonium chloride (lc); (2)Synthesis of con-taining aldehyde compounds:4-singleformyl-triphenylamine (2a),4-[(trans)-(4-nitrostyrylvinyl)]triphenylamine(2b),4-[(trans)-(4-menthylstyryl)]triphenyl a-mine(2c),4-formyl-4-[(trans)-(4-nitro-styryl)]triphenylamine(2d),4-formyl-4’-[(trans)-(4-methylstyryl)]triphe-nylamine(2e),4,4’-diformyltriph-enylamine (2f),1-p-tolyl-1H-indole-3-carbaldehyde(2g),4-[(trans)-(4-amino-phenyl)] triphenylamine (3a); (3) Synthesis oftarget compoundcontaining triphenyl-amineunits:4-[1-(4-me-thylphenyl)-3-methyl-imino-indole(trans)-(4 styryl)]triphenylamine(3b),4-[t-riphenylamine azomethine(trans)-(4-styryl)] triphenylamine(3c),4-[3,4-dih-ydroxyphenyl azomethine(trans)-(4-styryl)] triphenylamine(3 d),4-[1-(4-bromo-biphenyl)-3-methyl-indole-imino(trans)-(4-styryl)] triphenylam-ine(3e),4-[4,4’-(trans)-(styryl) triphenylamine azomethine(trans)-(4-styryl)]triphenylamine(3f);(4)Synthesis of triphenylam ine-based target compound containing fluorene ring:4-(4-triphenylamine azomethine)-2,7-dibromofluorene(4a),4,4’-dimethyl(2,7-dibromo-4-fluorenyl amino) triphenylamine (4b),4-[(trans)-(4-menthylstyryl)]-4’-triphenylam-ine azomethine-2,7-dibromo-fluorene(4c),bis-[4-(p-methylstyryl)-triphenyla mine]-4’-formyl biphenyl diamine bis-Schiffbase(5a),bis-[4-(p-methylstyr yl)-4’-formyl-taiphenylamine]phenyl-enediamine bis-Schiffbase(5b).Throu-gh testing the 1HNMR、13CNMR、IR spectrum of all intermediates and prod-ucts, the structures were characterized. We get the best synthesis conditions of intermediates 2b and 3 a through optimising synthesis experimental condit-ions.2. The study of the optical properties of 3b-3f,4a:(1) In dichloromethane, tetrahydrofuran,and acetonitrile solvent, the maximum absorption wavelength of 3b-3f and 4a were between 360-400nm, which showed some degrees of red-shift,compared to the triphenylamine;however, with the solvent polarity increasing, UV-Vis spectrum of these compounds occurre blue shift.(2) In Dichloromethane, tetrahydrofuran,or acetonitrile solvent,the fluorescence spectrums of the maximum emission wavelength of 3b-3f and 4a were between 440～550nm,which belonged to blue-green lightarea. However, their fluorescence emission spectrums of these Compounds(3b,3e,3f) occurre blue shift with the solvent polarity increasing.