Comparison of the structure property relationships in LB films of zwitterionic TCNQ adducts
作者:Norman A. Bell、Christopher S. Bradley、Richard A. Broughton、Simon J. Coles、David E. Hibbs、Michael B. Hursthouse、Asim K. Ray、Derek J. Simmonds、Stephen C. Thorpe
DOI:10.1039/b414325f
日期:——
Substitution reactions of TCNQ (7,7,8,8-tetracyanoquinodimethane) with suitable quinolinium and picolinium electron donor moieties yielded an extensive analogous series of α-bridged quinolinium and picolinium adducts R(2)Q3CNQ and R(2)P3CNQ respectively of which the long chain (Z)-β-[N-(1-hexadecyl)quinolinium-2-yl]-α-cyano-4-styryl}-dicyanomethanide (C16H33(2)Q3CNQ) is a typical example. These zwitterionic D–π–A materials (where D and A are electron donor and acceptor respectively) exhibit properties such as solvatochromism, molecular rectification and second harmonic generation and were compared and contrasted to the existing γ-bridged adducts. The behaviour of the materials on the water subphase and their resultant Langmuir–Blodgett (LB) film fabrication were studied. The abrupt change in molecular orientation in LB films of the γ-bridged adducts occurring at R = C15H31 and above was not seen in the more flatly orientated α-bridged adducts. Further characterisation of the LB films was performed using reflectance–absorption infra-red spectroscopy (RAIRS) and surface plasmon resonance (SPR). The crystal structure of the long chain adduct, C10H21(2)Q3CNQ, is also reported.
TCNQ(7,7,8,8-四氰基喹啉二甲基)与合适的喹啉和吡啶电子供体部分的取代反应,产生了大量类似的α-桥联喹啉和吡啶加合物R(2)Q3CNQ和R(2)P3CNQ,其中长链(Z)-β-[N-(1-十六烷基)喹啉-2-基]-α-氰基-4-苯乙烯基}-二氰基甲烷(C16H33(2)Q3CNQ)是一个典型例子。这些两性离子D-π-A材料(其中D和A分别是电子供体和受体)表现出溶剂致色、分子整流和二次谐波生成等特性,并与现有的γ-桥联加合物进行了比较和对比。研究了材料在水子相中的行为及其产生的Langmuir-Blodgett(LB)薄膜的制备。在R = C15H31及更高时,γ-桥联加合物在LB薄膜中的分子取向发生突然变化,而在取向更平坦的α-桥联加合物中则没有发生这种变化。使用反射-吸收红外光谱(RAIRS)和表面等离子共振(SPR)对LB薄膜进行了进一步表