Planar geometry of 4-substituted-2,2'-bipyridines synthesized by Sonogashira and Suzuki cross-coupling reactions
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TRUCTURE OF ORGANIC COMPOUNDS
Planar Geometry of 4-Substituted-2,2'-bipyridines Synthesized by Sonogashira and Suzuki Cross-Coupling Reactions1 T. T. Luong Thia, *, N. Nguyen Bicha, H. Nguyena, and L. Van Meerveltb, * a Chemistry
Department, Hanoi National University of Education, A4–136—Xuan Thuy—Cau Giay, Vietnam b Chemistry Department, KU Leuven, Celestijnenlaan 200F, B-3001, (Heverlee), Belgium *e-mail: [email protected]; [email protected] Received February 18, 2014
Abstract—Two 4-substituted 2,2'-bipyridines, namely 4-(ferrocenylethynyl)-2,2'-bipyridine (I) and 4-ferrocenyl-2,2'-bipyridine (II) have been synthesized and fully characterized via single-crystal X-ray diffraction and 1H and 13C NMR analyses. The π-conjugated system designed from 2,2'-bipyridine modified with the ferrocenylethynyl and ferrocenyl groups shows the desired planarity. In the crystal packing of I and II, the molecules arrange themselves in head-to-tail and head-to-head motifs, respectively, resulting in consecutive layers of ferrocene and pyridine moieties. DOI: 10.1134/S1063774515070160
INTRODUCTION The 2,2'-bipyridine is one of the most widely used chelate systems in coordination, supramolecular and macromolecular chemistry [1]. Due to their unique photophysical and photooptical properties, 2,2'-bipyridine derivatives are used in the synthesis of photosensitizers for dye sensitized solar cells (DSSC) [2, 3]. The introduction of different functionalities on the 2,2'-bipyridine moiety is based on the fact that larger delocalization of the π-electrons from the aromatic part of the molecule normally leads to higher extinction coefficients of the metal-to-ligand chargetransfer (MLCT) transitions in their copper(I) complexes [4]. In this paper, we report the synthesis, geometry and molecular arrangement in the crystals of two compounds, namely 4-(ferrocenylethynyl)-2,2'-bipyridine (I) and 4-ferrocenyl-2,2'-bipyridine (II) which were synthesized by the palladium catalyzed Sonogashira [5, 6] and Suzuki-Miyaura [7, 8] cross-coupling reactions. 1 The article is published in the original.
N Fe N I N Fe N II
EXPERIMENTAL Synthesis and crystallization. The synthesis of the compound 4-bromo-2,2'-bipyridine was achieved after three steps according to the procedure of Egbe et al. [9] with a total yield of 35%. All intermediates were fully characterized by spectroscopic methods. Procedure for the synthesis of 4-(ferrocenylethynyl)2,2'-bipyridine (I) by a palladium-catalyzed Sonogashira reaction. Toluene (4.0 mL) was deaerated by exchanging between vacuum and a stream of argon (three times). To this argon saturated solution were
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PLANAR GEOMETRY
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Experimental details
CCDC code Chemical formula Mr Crystal system, space group, Z a, b, c, Å; β, deg V, Å3 Crystal size, mm3 T, K Tmin, Tmax No. of measured, independent and observed [I > 2σ(I)] reflections Rint (sinθ/λ)max, Å–1 R [F 2 > 2 σ(F 2)], wR(F 2), S No. of reflections, parameters Δρmax, Δρmin, e Å–3
I
II
CCDC 1048373 C22H16FeN2 364.22 Monoclinic, Pc, 2 5.9175(2),
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