Dimethyl and diethyl esters of 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylic acid: a comparison

• Published in: Acta crystallographica. Section E, Crystallographic communications Vol. 72; no. 2; pp. 233 - 237
• Main Authors: Alfonso, Montserrat, Stoeckli-Evans, Helen
• Format: Journal Article
• Language: English
• Published: International Union of Crystallography 01.02.2016
• Subjects: crystal structure; C—H...O and C—H...N hydrogen bonding; dicarboxylic acid; diethyl; dimethyl; pyrazine; pyridine
• ISSN: 2056-9890; 2056-9890
• DOI: 10.1107/S2056989016001080

In dimethyl 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylate, C 18 H 14 N 4 O 4 , (I), and diethyl 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylate, C 20 H 18 N 4 O 4 , (II), the dimethyl and diethyl esters of 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylic 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), molecules are linked by C—H...N hydrogen bonds, forming chains along [001]. The chains are linked by C—H...π interactions, forming a three-dimensional structure. In the crystal of (II), molecules are linked via C—H...O hydrogen bonds, forming a three-dimensional framework. There are C—H...π interactions present within the framework.