Influence of methoxy groups on the properties of 1,1-bis(4-aminophenyl)cyclohexane based arylamines: experimental and theoretical approach
作者:Jonas Keruckas、Ramunas Lygaitis、Jurate Simokaitiene、Juozas Vidas Grazulevicius、Vygintas Jankauskas、Gjergji Sini
DOI:10.1039/c2jm14387a
日期:——
Three new isomeric cyclohexylidene linked triphenylamines containing methoxy groups in different positions were synthesized via Ullmann coupling from 1,1-bis(4-aminophenyl)cyclohexane and respective aryl iodides. Thermal behaviour, optical and photoelectrical properties of the obtained materials were investigated. Calculations based on the density functional methods (DFT) were also carried out in order to better understand structure–property relationships. Methoxy-substituted derivatives of 1,1-bis(4-aminophenyl)cyclohexane show lower ionization potentials and higher hole drift mobilities than the corresponding derivative having no methoxy groups. The ionization potentials of the solid samples of the methoxy-substituted compounds established by the electron photoemission technique are in the range of 5.34–5.55 eV. Hole-drift mobility values of the amorphous layers of the methoxy-substituted materials established by the time-of-flight technique range from 4.0 × 10−4 to 1.2 × 10−3 cm2 V−1 s−1 at the electric field of 106 V cm−1. The highest hole mobilities were observed for the para-substituted derivative. Theoretical results suggest that the hole mobility in the bulk materials is driven by the electronic coupling parameter whilst the reorganization energy parameter predicts the wrong mobility trend. The role of the methoxy groups is found to be related to the well-known mesomeric (π-donor) effect and the possibility to establish C–H⋯π(Ph) and C–H⋯X (X = O, N) hydrogen bonds. The effect of these properties on the enhanced Stokes shifts of the para-methoxy-substituted compound, on the decrease of the ionization potentials for the methoxy substituted compounds as compared to the non-substituted one, and on the enhanced possibility to establish considerable electronic couplings between adjacent molecules is discussed in detail.
合成了三种新型异构体的环己烯基连接的三苯胺,这些化合物在不同位置含有甲氧基。它们通过乌尔曼耦合从1,1-双(4-氨基苯基)环己烷和相应的芳基碘化物合成。研究了所获得材料的热行为、光学和光电属性。还基于密度泛函理论(DFT)进行了计算,以更好地理解结构-性质关系。与不含甲氧基的相应衍生物相比,1,1-双(4-氨基苯基)环己烷的甲氧基取代衍生物显示出较低的电离势和较高的空穴漂移迁移率。采用电子光发射技术确定的甲氧基取代化合物的固体样品电离势范围为5.34–5.55 eV。在106 V cm−1电场下,采用飞行时间技术确定的甲氧基取代材料的非晶态层的空穴漂移迁移率值介于4.0 × 10−4至1.2 × 10−3 cm2 V−1 s−1之间。对位取代衍生物的空穴迁移率最高。理论结果表明,块体材料中的空穴迁移率受电子耦合参数的驱动,而重组能量参数则预测了错误的迁移率趋势。发现甲氧基的作用与众所周知的共振(π-供体)效应有关,并且能够形成C–H⋯π(苯)和C–H⋯X(X = O, N)氢键。详细讨论了这些属性对对位甲氧基取代化合物的增强斯托克斯位移、与不取代化合物相比甲氧基取代化合物电离势的降低,以及在相邻分子之间建立显著电子耦合的增强可能性所产生的影响。