Alfonso Montserrat, Stoeckli-Evans Helen
Institute of Chemistry, University of Neuchâtel, Av. de Bellevaux 51, CH-2000 Neuchâtel, Switzerland.
Insitute of Physics, University of Neuchâtel, rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland.
Acta Crystallogr E Crystallogr Commun. 2016 Jan 27;72(Pt 2):233-7. doi: 10.1107/S2056989016001080. eCollection 2016 Feb 1.
In dimethyl 5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxyl-ate, C18H14N4O4, (I), and diethyl 5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carboxyl-ate, C20H18N4O4, (II), the dimethyl and diethyl esters of 5,6-bis-(pyridin-2-yl)pyrazine-2,3-di-carb-oxy-lic acid, the orientation of the two pyridine rings differ. In (I), pyridine ring B is inclined to pyrazine ring A by 44.8 (2)° and the pyridine and pyrazine N atoms are trans to one another, while pyridine ring C is inclined to the pyrazine ring by 50.3 (2)°, with the pyridine and pyrazine N atoms cis to one another. In compound (II), the diethyl ester, which possesses twofold rotation symmetry, the pyridine ring is inclined to the pyrazine ring by 40.7 (1)°, with the pyridine and pyrazine N atoms trans to one another. In the crystal of (I), mol-ecules are linked by C-H⋯N hydrogen bonds, forming chains along [001]. The chains are linked by C-H⋯π inter-actions, forming a three-dimensional structure. In the crystal of (II), mol-ecules are linked via C-H⋯O hydrogen bonds, forming a three-dimensional framework. There are C-H⋯π inter-actions present within the framework.
在5,6 - 双 -（吡啶 - 2 - 基）吡嗪 - 2,3 - 二羧酸二甲酯（C₁₈H₁₄N₄O₄，（I））和5,6 - 双 -（吡啶 - 2 - 基）吡嗪 - 2,3 - 二羧酸二乙酯（C₂₀H₁₈N₄O₄，（II））中，即5,6 - 双 -（吡啶 - 2 - 基）吡嗪 - 2,3 - 二羧酸的二甲酯和二乙酯中，两个吡啶环的取向不同。在（I）中，吡啶环B相对于吡嗪环A倾斜44.8（2）°，吡啶和吡嗪的N原子彼此反式排列，而吡啶环C相对于吡嗪环倾斜50.3（2）°，吡啶和吡嗪的N原子彼此顺式排列。在化合物（II）即二乙酯中，其具有二重旋转对称性，吡啶环相对于吡嗪环倾斜40.7（1）°，吡啶和吡嗪的N原子彼此反式排列。在（I）的晶体中，分子通过C - H⋯N氢键相连，沿[001]方向形成链状结构。这些链通过C - H⋯π相互作用相连，形成三维结构。在（II）的晶体中，分子通过C - H⋯O氢键相连，形成三维骨架。在该骨架内存在C - H⋯π相互作用。
