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Structures of 2,5-diaryl- and 2,3,5,6-tetra[3,2-b]thiophene synthesized by the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction

The crystal structures of 2,5-di(ethoxyphenyl)-3,6-dibromothieno[3,2-b]thiophene (I) and 2,5-di(ethoxyphenyl)- 3,6-diphenylthieno[3,2-b]thiophene (II) have been studied in order to evaluate the planarity of these molecules. The aromatic systems introduced to the thieno[3,2-b]thiophene core structure show a degree of rotation from 30.94 to 66.56 . The crystal packing of (I) are characterized by π π stacking, while in (II), C-H and C-H O interactions are observed. | Vietnam Journal of Chemistry, International Edition, 54(6): 672-677, 2016 DOI: 10.15625/0866-7144.2016-00385 Structures of 2,5-diaryl- and 2,3,5,6-tetra[3,2-b]thiophene synthesized by the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction Nguyen Hien1*, Nguyen Bich Ngan1, Nguyen Dang Dat1, Luc van Meervelt2 1 Faculty of Chemistry, Hanoi National University of Education 2 Department of Chemistry, KU Leuven Received 10 August 2016; Accepted for publication 19 December 2016 Abstract The crystal structures of 2,5-di(ethoxyphenyl)-3,6-dibromothieno[3,2-b]thiophene (I) and 2,5-di(ethoxyphenyl)3,6-diphenylthieno[3,2-b]thiophene (II) have been studied in order to evaluate the planarity of these molecules. The aromatic systems introduced to the thieno[3,2-b]thiophene core structure show a degree of rotation from 30.94 to 66.56 . The crystal packing of (I) are characterized by π π stacking, while in (II), C-H and C-H O interactions are observed. Keywords. thieno[3,2-b]thiophene, palladium-catalyzed, Suzuki-Miyaura, cross-coupling. 1. INTRODUCTION Thieno[3,2-b]thiophene possesses a rigid structure and an extended π-conjugation. This electron-rich two annulated thiophene structure enable it to construct conjugated and low band gap organic semiconductors. Functionalized thieno[3,2b]thiophene units have been incorporated into, or designed as a part of the skeleton of conjugated oligomers and polymers to improve the electronic properties of the materials [1]. These kinds of materials were applied to produce high-performance organic field-effect transistors (OFETs) [2], organic light-emitting diodes (OLEDs) [3], and photovoltaics devices [4]. In fact, the performance of a functionalized material depends heavily on its molecular structure and the stacking motif. Therefore, design of functional molecular solid-state 2. EXPERIMENTAL 2.1. Chemicals structures, or arrangements, through tuning of the intermolecular interactions is essential. One of the convenient methods