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

摘要

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), 2C(4)H(6)N(4)center dot C4H8O2, (II), 2,4-diaminopyrimidine-N, N-dimethylacetamide (1/1), C4H6N4 center dot C4H9NO, (III), and 2,4-diaminopyrimidine-1-methylpyrrolidin-2-one (1/1), C4H6N4 center dot C5H9NO, (IV), one salt of barbituric acid, viz. 2,4-diaminopyrimidinium barbiturate (barbiturate is 2,4,6-trioxopyrimidin-5-ide), C4H7N4+center dot 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+center dot C4H3N2O2S-center dot 2C(3)H(7)NO, (VI), and 2,4-diaminopyrimidinium 2-thiobarbiturate-N, N-dimethylacetamide (1/2), C4H7N4+center dot C4H3N2O2S-center dot 2C(4)H(9)NO, (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), R-2(2)(8) N-H center dot center dot center dot N hydrogen-bond motifs are preferred and, in two structures, additional R-3(2)(8) patterns were observed.