One barbiturate and two solvated thiobarbiturates containing the triply hydrogen-bonded ADA/DAD synthon, plus one ansolvate and three solvates of their coformer 2,4-diaminopyrimidine

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• 作者：Wilhelm Maximilian Hü ; tzler ; Ernst Egert and Michael Bolte
• 关键词：crystal engineering ; barbiturates ; synthon ; cocrystals ; hydrogen bonding ; 2 ; 4-diaminopyrimidine ; barbituric acid ; 2-thiobarbituric acid
• 刊名：Acta Crystallographica Section C
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：72
• 期：9
• 页码：705-715
• 全文大小：2367K
• ISSN：1600-5759

文摘

A path to new synthons for application in crystal engineering is the replacement of a strong hydrogen-bond acceptor, like a C=O group, with a weaker acceptor, like a C=S group, in doubly or triply hydrogen-bonded synthons. For instance, if the C=O group at the 2-position of barbituric acid is changed into a C=S group, 2-thiobarbituric acid is obtained. Each of the compounds comprises two ADA hydrogen-bonding sites (D = donor and A = acceptor). We report the results of cocrystallization experiments of barbituric acid and 2-thiobarbituric acid, respectively, with 2,4-diaminopyrimidine, which contains a complementary DAD hydrogen-bonding site and is therefore capable of forming an ADA/DAD synthon with barbituric acid and 2-thiobarbituric acid. In addition, pure 2,4-diaminopyrimidine was crystallized in order to study its preferred hydrogen-bonding motifs. The experiments yielded one ansolvate of 2,4-diaminopyrimidine (pyrimidine-2,4-diamine, DAPY), C₄H₆N₄, (I), three solvates of DAPY, namely 2,4-diaminopyrimidine–1,4-dioxane (2/1), 2C₄H₆N₄·C₄H₈O₂, (II), 2,4-diaminopyrimidine–N,N-dimethylacetamide (1/1), C₄H₆N₄·C₄H₉NO, (III), and 2,4-diaminopyrimidine–1-methylpyrrolidin-2-one (1/1), C₄H₆N₄·C₅H₉NO, (IV), one salt of barbituric acid, viz. 2,4-diaminopyrimidinium barbiturate (barbiturate is 2,4,6-trioxopyrimidin-5-ide), C₄H₇N₄⁺·C₄H₃N₂O₃⁻, (V), and two solvated salts of 2-thiobarbituric acid, viz. 2,4-diaminopyrimidinium 2-thiobarbiturate–N,N-dimethylformamide (1/2) (2-thiobarbiturate is 4,6-dioxo-2-sulfanylidenepyrimidin-5-ide), C₄H₇N₄⁺·C₄H₃N₂O₂S⁻·2C₃H₇NO, (VI), and 2,4-diaminopyrimidinium 2-thiobarbiturate–N,N-dimethylacetamide (1/2), C₄H₇N₄⁺·C₄H₃N₂O₂S⁻·2C₄H₉NO, (VII). The ADA/DAD synthon was succesfully formed in the salt of barbituric acid, i.e. (V), as well as in the salts of 2-thiobarbituric acid, i.e. (VI) and (VII). In the crystal structures of 2,4-diaminopyrimidine, i.e. (I)–(IV), R₂²(8) N—H…N hydrogen-bond motifs are preferred and, in two structures, additional R₃²(8) patterns were observed.