以材料为导向的有机分子及其合成综述#
 

摘要：有机共轭分子在有机光电材料方面的应用吸引了越来越多的关注。由于有机分子良好的延展性和经济性，尤其是有机共轭分子优良的导电性质，而且随着共轭程度的不同会发出各种不同波长的光，因此在有机光电领域，如有机场效应晶体管(OFET)，有机太阳能电池和有机发光二极管(OLED)等方面都有广泛的应用。其中有些材料的性质甚至超过了常用的无机和高分子材料。通过有机合成的手段构建和修饰分子结构以提高有机共轭分子的性能是该领域的首要任务。本文综述了几类有机共轭分子常见的合成方法及应用。
 

关键词：有机化学；共轭分子；有机合成

0 引言
具有光电性质的有机共轭分子是光电器件的基础。自从聚乙炔(polyacetylene)被发现具有导电性质以来[1-3]，研究共轭分子的合成，物理及化学性质随之成为蓬勃发展的新兴领域。这些共轭分子具有许多有趣而有用的光电及非线性光学性质，使之成为一些电子器件的主要成分。尤其是20 世纪90 年代初，利用polyphenylenevinylene(PPV)作为发光二极管器件的材料促使了对共轭分子光电性质的积极研究。
 

有机共轭分子有较高的HOMO 及较低的LUMO 的能阶，共轭的长度愈长，HOMO 及LUMO 的能量差愈小，这就是有机共轭分子具有特殊光电性质的基础。其吸收或荧光的波长，随着共轭基团的长度，杂原子的种类以及其取代基的不同而不同[4]。但是当共轭长度达到一定极限时，HOMO 及LOMO 的能量差不再变化[5]。一般而言，有机共轭分子的能量差恰好落在半导体的导电带(conducting band)及价带(valence band)的能量差，故有机共轭分子的电性可以用半导体的能带理论(band theory)来解释。再者，这些分子的吸收波长刚好在可见光的范围，这是它们可以用作光电材料的基础[6]。
 

光电分子材料是由数以兆计的单个分子组装的薄膜或单晶，因此它们的性质可以宏观的尺度来表征，例如薄膜晶体管(thin film tranststor, TFT)，液晶显示器(liquid crystal display)及有机发光二极管(organic light emitting diode, OLED)等都是利用分子材料的电子组件，这是集化学，物理，材料科学，工程以及计算机等领域智慧的结晶。
 

分子电子学(molecular electronics 45 或moletronics)是一门新兴的领域，与光电分子材料不同的是分子电子是利用单一或一小簇(数以千计)的分子作为电子组件的基本单元制成的线路(circuit)，开关(switch)和内存(ram)等。例如Pentium4 的芯片(chips)只有约几个平方厘米却含有4200 万个晶体管。这就是一个典型的有机分子，可占有的空间约1–3nm，这时每平方厘米可容纳1014 个分子，其密度是超过目前半导体的100 万倍，比起半导体预估的极限，分子电子可能还要小数十倍。然而到目前为止，如何将这1014 个分子串联起来仍是一个难题[7]。无论是分子电子还是光电分子材料，绝大多数都是具有半导体性质的有机共轭分子。具有不同官能团的分子有不同的用途，这使得在分子设计上更是丰富多彩。

3 结论
目前，以光电材料为导向的有机化合物以及分子电子学迅速发展，尤其是随着杂原子(硫，氧，磷和硅等)的引入，合成方法不断更新，测试手段和仪器不断优化，极大促进了该领域的发展。作为分子电子学的重要组成部分，分子线研究发展迅速，寡聚苯乙烯和寡聚苯乙炔类化合物在分子线中的研究取得令人满意的结果，噻吩和呋喃衍生物在光电材料的应用也有长足的发展。本组对几类有机共轭分子进行了合成及性质的研究。简洁高效合成各种功能分子将成为今后有机合成化学的热点领域。
 

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