Thiophene-benzoquinones: synthesis, crystal structures and preliminary coordination chemistry of derived anilate ligands
作者:Matteo Atzori、Flavia Pop、Thomas Cauchy、Maria Laura Mercuri、Narcis Avarvari
DOI:10.1039/c4ob01582g
日期:——
2,5-Bis(thiophene) and 2,5-bis(ethylenedioxy-thiophene) (EDOT) derivatives of 3,6-diethoxy-1,4-benzoquinone (para isomers) were prepared by Stille coupling between the 2,5-dibromo-3,6-diethoxy-1,4-benzoquinone precursors and (n-Bu)3Sn-R (R = 2-thiophenyl or 3,4-ethylenedioxy-2-thiophenyl) reagents. In a parallel series of experiments 2,6-bis(thiophene) and 2,6-EDOT-3,5-diethoxy-1,4-benzoquinone (meta isomers) were synthesized by the same strategy. The four compounds were structurally characterized. The thiophene derivatives show essentially planar conformation thanks to the conjugation and establishment of S⋯O 1,5-nonbonded interactions, while in the EDOT derivatives the thiophene moieties are twisted with respect to the benzoquinone ring because of the steric hindrance. TD-DFT calculations were performed on both para and meta thiophene isomers in order to explain the differences observed in the UV-Vis absorption spectra. The 2,5-derivatives are valuable precursors for thiophene containing anilate (An) ligands, as the first examples of electron rich substituent based anilates. The Cu(II) complex [Cu(Th2An)(tbbpy)]·2H2O (Th2An = thiophene-anilate; tbbpy = 4,4′-bis(tert-butyl)-2,2′-bipyridine) was isolated and structurally characterized. The metal center lies within a square planar coordination geometry, while the ligands engage in a set of intermolecular contacts.
通过 2,5-二溴-3,6-二乙氧基-1,4-苯醌前体与 (n-Bu)3Sn-R (R = 2-thiophenyl 或 3,4-ethylenedioxy-2-thiophenyl) 试剂之间的 Stille 偶联,制备了 3,6-二乙氧基-1,4-苯醌的 2,5-双(噻吩)和 2,5-双(亚乙二氧基噻吩)(EDOT) 衍生物(对位异构体)。在一系列平行实验中,采用相同的策略合成了 2,6-双(噻吩)和 2,6-EDOT-3,5-二乙氧基-1,4-苯醌(元异构体)。对这四种化合物进行了结构表征。由于共轭和 S⋯O 1,5 非键相互作用的建立,噻吩衍生物基本上呈平面构象,而在 EDOT 衍生物中,由于立体阻碍,噻吩分子相对于苯醌环是扭曲的。为了解释紫外可见吸收光谱中观察到的差异,我们对对位和偏位噻吩异构体进行了 TD-DFT 计算。这些 2,5 衍生物是含苯胺酸盐(An)配体的噻吩的重要前体,也是首例富电子取代基苯胺酸盐。我们分离出了 Cu(II) 复合物 [Cu(Th2An)(tbbpy)]-2H2O(Th2An = 噻吩苯甲酸盐;tbbpy = 4,4′-双(叔丁基)-2,2′-联吡啶),并对其进行了结构表征。金属中心位于一个方形平面配位几何中,而配体则有一系列分子间接触。