烷氧基桥接的苯并菲和苝单亚胺二酯二元化合物的合成及性质研究

Synthesis and Properties of Alkoxy-Bridged Triphenylene and Perylene Monoimide Diesters Dyads

柱状相盘状液晶材料具有较高的载流子迁移率,而给体-桥-受体型超分子具有光诱导分子内电子转移的性质.为了使材料兼有这两种性质,我们合成了柔性烷氧基桥连接的、含有苯并菲单元和苝单亚胺二酯单元的二元化合物.其分子结构通过~1H NMR,IR,MS和元素分析进行表征.此外,循环伏安法测试结果表明二元化合物中两个结构单元的能级分别与对应单体的能级保持一致.稀溶液中的紫外可见吸收光谱及荧光光谱结果表明,光照时在给体单元和受体单元间发生有效的能量转移和电子转移.示差扫描热分析仪及偏光显微镜的测试结果表明当桥链碳原子数为10和12的二元化合物在加热时可形成稳定的液晶柱状相.由此可知,该类化合物具有作为新型有机光伏材料的前景.

Columnar discotic liquid crystals have high charge carrier mobility, and donor-bridge-accepter-based supra-molecular compounds have photoinduced intramolecular electron transfer behavior. In order to make the organic materials possess these two performances, dyads composed of hexaalkoxy triphenylene unit and perylene monoimide diesters unit were prepared in this work. In the dyads, the flexible alkoxys were used as bridges, the triphenylene units having six electron-donating alkoxy tails acted as electron donors, and the perylene monoimide diesters units having four electron-withdrawing carbonyls acted as electron acceptors. Their structures were established by proton nuclear magnetic resonance（1H NMR）, infrared spectroscopy（IR）, mass spectrometry（MS） and elemental analysis（EA）. The photophysical properties were characterized by means of UV-Vis absorption spectroscopy and fluorescence spectroscopy. The results showed that in dilute dichloromethane solutions the absorbance strength of these dyads was the sum of that of their monomers, hexakishexyloxy triphenylene（HAT6） and N-hexyl-perylene monoimide dihexyl esters（PMD6）, and not interfered by the length of flexible bridges. When excited at 475 nm, the strength of the fluorescence of the dyads decreased when the spacers shortened from dodecyloxy, decyloxy, hexyloxy to ethoxy groups. Actually, when the spacer was ethoxy group, the fluorescence of the dyad was almost quenched completely. This is attributed to the photoinduced electron transfer properties（PET） between the donor and acceptor units. When excited at 280 nm, the strength of the fluorescence of the triphenylene units also became weaker when the spacers shortened from dodecyloxy to ethanyloxy. At the same time, the strength of the fluorescence of the perylene units became stronger. This is attributed to energy transfer from the triphenylene unit to the perylene unit. In addition, their liquid crystalline properties have been studied by polarized optical microscopy（POM） and differential scanning calorimetry（DSC）. The results demonstrated that when the spacers were decyloxy and dodecyloxy the dyads possessed columnar liquid crystal behavior in the heating circle, while in the cooling circle only the dyad bearing the dodecyloxy spacer showed mesophase; and dyads bridged by the hexyloxy or ethanyloxy did not show liquid crystal properties in the heating or cooling circle. Electronic energy levels of triphenylene and perylene units of the dyads measured by cyclic voltammetry（CV） are almost the same as that of HAT6 and PMD6, respectively. In conclusion, these dyads have the potential application in the organic photovoltaic field.