Synthesis of tris, tetrakis, and pentakisazo dyes and their application to guest–host liquid crystal displays
作者:Masaki Matsui、Kazunori Shirai、Naoki Tanaka、Kazumasa Funabiki、Hiroshige Muramatsu、Katsuyoshi Shibata、Yasuo Abe、Yuji Ohgomori
DOI:10.1039/a905852d
日期:——
Tris-, tetrakis-, and pentakisazo dyes have been prepared by the oxidation of 4-(arylazo)arylamines. Iodobenzene diacetate was the preferred oxidant for preparation of 4,4â²-bis(arylazo)azobenzenes and 4,4â²-bis(arylazo)-2,2â²,3,3â²,5,5â²,6,6â²-octafluoroazobenzenes, whereas silver(II) oxide proved a satisfactory oxidant for synthesis of 4,4â²-(arylazo)(methyl-substituted)azobenzenes. Unsymmetrical tris- and tetrakisazo dyes were also obtained by cross oxidation. The absorption bands of these azo dyes were observed in the range of 381â472Â nm in liquid crystals. The solubility of the trisazo dyes in hexane was the highest, followed by the tetrakis- and pentakisazo dyes. The unsymmetrical derivative having methyl groups in the central p-phenylene moieties was most soluble among the trisazo dyes. The order parameters (S) of the tris-, tetrakis-, and pentakisazo derivatives were in the range 0.66â0.81, sufficiently high for the practical application of these dyes in liquid crystal displays.
三重、四重和五重偶氮染料是通过氧化4-(芳基偶氮)芳胺制备的。二乙酸碘苯是制备4,4'-双(芳基偶氮)偶氮苯和4,4'-双(芳基偶氮)-2,2',3,3',5,5',6,6'-八氟偶氮苯的首选氧化剂,而银(II)氧化物对于合成4,4'-(芳基偶氮)(甲基取代)偶氮苯则证明是一种满意的氧化剂。还通过交叉氧化获得了不对称的三重和四重偶氮染料。这些偶氮染料的吸收带在液晶中观察到的范围为381–472 nm。三重偶氮染料在己烷中的溶解度最高,其次是四重和五重偶氮染料。具有中央对苯基团的甲基取代的不对称衍生物在三重偶氮染料中溶解度最高。三重、四重和五重偶氮衍生物的序列参数(S)在0.66–0.81范围内,足够高以便在液晶显示器中实际应用这些染料。