醌型木素模型物的光学特性  

Optical Characteristics of Lignin with a Quinoid Structure

作　　者：陈晓华[1] 樊永明[1] 曹春昱[2] 胡红智[3] 

机构地区：[1]北京林业大学材料科学与技术学院,北京100083 [2]中国制浆造纸研究院,北京100020 [3]北京师范大学化学学院,北京100875

出　　处：《物理化学学报》2010年第1期125-130,共6页Acta Physico-Chimica Sinica

基　　金：国家十一五科技支撑计划课题(2006BAD32B04)资助项目~~

摘　　要：为探索醌型木素化学结构与颜色的关系,以五种醌型木素模型物2-甲氧基-1,4-苯醌(I)、1,2-苯醌(II)、4-亚烯丙基-2-甲氧基-2,5-环己二烯酮(亚甲基醌)(III)、5-甲氧基-1,4-苯醌-2-氧负离子(IV)和5-甲基-1,4-苯醌-2-氧负离子(V)作为纸浆中醌型木素发色体的代表,在B3LYP/6-311++G(2d,p)水平上获得了它们在乙醇中的稳定基态构型,采用含时密度泛函理论(TD-DFT)在同等水平上计算了其在乙醇溶液中的电子光谱,并分析了它们在可见光范围内的吸收.结果发现:五种模型物在可见光范围内的吸收均源于电子的π→π*跃迁,它们的最大吸收波长顺序依次为III<I<II<IV<V,吸光系数顺序依次为IV<I<V<II<III;漂白过程中生成的醌氧负离子以及邻醌类模型物具有中等大小的吸光系数(ε=1978-3197),吸收波长较长(445.47-552.36 nm),是漂白后纸浆具有颜色的重要原因.对醌类模型物吸收波长较小(414.91 nm),吸光系数大小为中等(ε=2094),亚甲基醌类模型物虽然吸光系数大(ε=31935),但吸收波长较小(407.90 nm),二者对漂白后纸浆的颜色影响较小.To explore the relationship between the structures and color of a quinoid lignin,quantum chemical calculations on five model lignin compounds： 2-methoxy-1,4-benzoquinone（I）,1,2-benzoquinone（II）,4-acrol-2-methoxy-2,5-cyclohexadienone（p-quinone methide）（III）,5-methoxy-1,4-benzoquinone-2-oxygen anion（IV）,5-methyl-1,4-benzoquinone-2-oxygen anion（V） were performed using density functional theory at the B3LYP/6-311＋＋G（2d,p） level.Optimized structures were obtained using ethanol as a solvent.Electronic spectra were produced using time dependent density functional theory（TD-DFT） at the same level.Results indicated that the maximum absorption band in the visibleregion of the five model compounds was caused by a π→π＊ transition.The location of the maximum absorption bandincreased according to： IIIIIIIVV.The oscillation strength at the maximum absorption band increased accordingto： IVIVIIIII.The quinone oxygen anion and the o-quinone model compounds that were produced during thebleaching process had average extinction coefficients（ε=1978-3197） at 445.47-552.36 nm in the visible light region,which would be an important color source for pulp after bleaching.Although the p-quinone model compound had anaverage extinction coefficient（ε=2094） and quinone methide had a large extinction coefficient（ε=31935）,they did nothave much effect on the color of the bleached pulp because of their comparatively short absorption wavelengths（414.91 and 407.90 nm,respectively）.

关 键 词：密度泛函理论 醌型木素 含时密度泛函理论 光学特性 电子光谱 

分 类 号：O636.2[理学—高分子化学]