a 南昌工程学院 理学院 江西省南昌市天祥大道289号 330099;
b 兰州大学 功能有机分子化学国家重点实验室 甘肃省兰州市天水南路222号 730000
Flexible TTF Derivatives: Synthesis, Structure and Self-assembly
Zhang Shangxia, Shao Xiangfengb
a School of Science, Nanchang Institute of Technology, Tianxiang Road 289, Nanchang 330099, Jiangxi Province, China;
b State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Tianshui Southern Road 222, Lanzhou 730000, Gansu Province, China
Organic electron donors with planar configuration, moderate redox potential and favorable flexibility are the foundation of the molecular material science and self-assembly chemistry. In this work, a series of TTF derivatives (TTF1~TTF8) with well molecule flexibility have been synthesized employing a copper-mediated C-S coupling reaction of 1,2-diiodophenyl groups and a zinc-thiolate complex, (TBA)2[Zn(DMIT)2] (TBA=tetrabutyl ammonium, DMIT=1,3-dithiole-2-thione-4,5-dithiolate) as the key step. The physicochemical properties and crystal structures of these TTFs are fully investigated by UV/Vis absorption spectra, cyclic voltammetry, single crystal X-ray diffraction. The ethylenedioxy/ethylenedithio group and sulfur attached phenyl groups leads to unusual properties of TTFs series. In comparison with TTF5~TTF8 containing ethylenedithio groups, TTF1~TTF4 substituted by ethylenedioxy groups exhibit stronger absorbance, due to the different electronegative of oxygen and sulfur atom. In addition the absorbance is reducing progressively as the electron donating ability of the respective aryl groups increasing. By introducing fused aryls, the first half redox potential(E1/21) used to estimate the electrochemical stability of different organic electron donors of the TTF derivatives are much higher than that of BEDT-TTF and TTF itself. The aryls ensure the stability of TTF-core via dispersing its electrons. By hot recrystallization or slowly evaporating the solvent, single crystals of eight TTFs suitable for single-crystal X-ray diffraction measurement were obtained. All these TTF derivatives adopt boat conformation with various dihedral angles between the central C2S4 plane with the terminal C2O2 and C2S2 plane of the TTF framework. Complicated aryls leads to larger dihedral angles. TTF5~TTF8 with ethylenedithio groups have more dominant curving configuration with respect to TTF1~TTF4 functionalized by ethylenedioxy groups. Additionally, the stereo-hindrance effects due to the fused phenyl groups prolong the distance from one molecule to another. As a typical example of crystal structure of TTF4, in which the tow methoxy groups make the distance much longer than that in TTF1. Furthermore, the C-S bond vibrate upon and down the TTF-skeleton plane, brings properties on self-assembly chemistry for the flexible TTFs. Single crystals of the complex (TTF4)(C60) are obtained via slowly evaporating chlorobenzene at room temperature after the mixture was heated and refluxed for five minutes. The dihedral angles of TTF4 enlarges to same extent from 24.30° to 30.17°, reveals that the TTFs connected by C-S bridge bond might control their configuration as circumstance changing while participating in self-assembly with various guests.