Synthesis, linear and nonlinear optical properties of phosphonato-substituted bithiophenes derived from 2,2′-biphenol
作者:Jason L. Freeman、Qun Zhao、Yuanli Zhang、Jianwei Wang、Christopher M. Lawson、Gary M. Gray
DOI:10.1039/c3dt51499d
日期:——
Two new series of phosphonato-substituted bithiophenes, BpP(X)(C4H2S)2H and BpP(X)(C4H2S)2P(X)Bp (Bp = 2,2â²-C12H8O2, X = O, S, Se), have been synthesized and characterized using linear absorption and emission spectra, and third-order nonlinear absorption measurements at 430 nm with 27 ps laser pulses. The compounds were synthesized in three steps: (1) reacting lithiated bithiophene with (Et2N)2PCl; (2) reacting the product from the first step with biphenol; and (3) reacting the product from the second step with the appropriate chalcogen. The X-ray crystal structures of two of the compounds, BpP(O)(C4H2S)2P(O)Bp and BpP(Se)(C4H2S)2P(Se)Bp, are reported and show a number of intermolecular ÏâÏ interactions. The linear absorption spectra, emission spectra, and emission quantum yields show distinct trends with respect to the chalcogen and the number of phosphorus substituents attached to the 2,2â²-bithiophene ring. The compounds show emission maxima at wavelengths ranging from 380â400 nm and, BpP(S)(C4H2S)2H shows a 23-fold increase in fluorescence quantum yield relative to that of 2,2â²-bithiophene. Fluorescence lifetimes and radiative and non-radiative decay rate constants for the first singlet excited state have been extracted from the quantum yields using time-dependent DFT calculations. Nonlinear transmission measurements indicate that all of the compounds show nonlinear absorption at 430 nm with 27 ps laser pulses in spite of their low solubilities. Notably, the nonlinear absorption threshold of a 0.16 mol Lâ1 CH2Cl2 solution of BpP(Se)(C4H2S)2H is 0.9 J cmâ2. The excellent emission quantum yields and good nonlinear absorptions make these compounds promising candidates for optical power limiting applications and as host materials for violet-blue organic light emitting diodes.
合成并表征了两种新的磷酸酯取代的双噻吩系列化合物BpP(X)(C4H2S)2H和BpP(X)(C4H2S)2P(X)Bp(Bp = 2,2'-C12H8O2,X = O,S,Se),使用线性吸收和发射光谱,以及在430 nm波长下利用27 ps激光脉冲进行的三阶非线性吸收测量。这些化合物的合成分为三个步骤:(1)将锂化的双噻吩与(Et2N)2PCl反应;(2)将第一步的产物与联苯酚反应;(3)将第二步的产物与相应的化学元素反应。报告了两种化合物BpP(O)(C4H2S)2P(O)Bp和BpP(Se)(C4H2S)2P(Se)Bp的X射线晶体结构,显示了一些分子间的π–π相互作用。线性吸收光谱、发射光谱和发射量子产率显示出相对于化学元素及附着于2,2'-双噻吩环的磷替代体数量的明显趋势。这些化合物在380–400 nm波长范围内显示出发射最大值,其中BpP(S)(C4H2S)2H的荧光量子产率相对于2,2'-双噻吩增加了23倍。通过时间相关的密度泛函理论计算,从量子产率中提取了第一激发单态的荧光寿命和辐射与非辐射衰减速率常数。非线性传输测量显示,尽管这些化合物的溶解度较低,但在430 nm波长下使用27 ps激光脉冲时均表现出非线性吸收。值得注意的是,0.16 mol L⁻¹ CH2Cl2溶液中BpP(Se)(C4H2S)2H的非线性吸收阈值为0.9 J cm⁻²。优异的发射量子产率和良好的非线性吸收使这些化合物成为光功率限制应用和紫蓝色有机发光二极管的宿主材料的有希望的候选者。