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Sulfur as hydrogen‐bond acceptor in cocrystals of 2‐thio‐modified thymine
Author(s) -
Hützler Wilhelm Maximilian,
Bolte Michael
Publication year - 2018
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229617017181
Subject(s) - synthon , cocrystal , chemistry , hydrogen bond , crystal engineering , acceptor , medicinal chemistry , crystal structure , stereochemistry , crystallography , molecule , organic chemistry , physics , condensed matter physics
Doubly and triply hydrogen‐bonded supramolecular synthons are of particular interest for the rational design of crystal and cocrystal structures in crystal engineering since they show a high robustness due to their high stability and good reliability. The compound 5‐methyl‐2‐thiouracil (2‐thiothymine) contains an ADA hydrogen‐bonding site ( A = acceptor and D = donor) if the S atom is considered as an acceptor. We report herein the results of cocrystallization experiments with the coformers 2,4‐diaminopyrimidine, 2,4‐diamino‐6‐phenyl‐1,3,5‐triazine, 6‐amino‐3 H ‐isocytosine and melamine, which contain complementary DAD hydrogen‐bonding sites and, therefore, should be capable of forming a mixed ADA – DAD N—H…S/N—H…N/N—H…O synthon (denoted synthon 3 s N·S;N·N;N·O ), consisting of three different hydrogen bonds with 5‐methyl‐2‐thiouracil. The experiments yielded one cocrystal and five solvated cocrystals, namely 5‐methyl‐2‐thiouracil–2,4‐diaminopyrimidine (1/2), C 5 H 6 N 2 OS·2C 4 H 6 N 4 , (I), 5‐methyl‐2‐thiouracil–2,4‐diaminopyrimidine– N , N ‐dimethylformamide (2/2/1), 2C 5 H 6 N 2 OS·2C 4 H 6 N 4 ·C 3 H 7 NO, (II), 5‐methyl‐2‐thiouracil–2,4‐diamino‐6‐phenyl‐1,3,5‐triazine– N , N ‐dimethylformamide (2/2/1), 2C 5 H 6 N 2 OS·2C 9 H 9 N 5 ·C 3 H 7 NO, (III), 5‐methyl‐2‐thiouracil–6‐amino‐3 H ‐isocytosine– N , N ‐dimethylformamide (2/2/1), (IV), 2C 5 H 6 N 2 OS·2C 4 H 6 N 4 O·C 3 H 7 NO, (IV), 5‐methyl‐2‐thiouracil–6‐amino‐3 H ‐isocytosine– N , N ‐dimethylacetamide (2/2/1), 2C 5 H 6 N 2 OS·2C 4 H 6 N 4 O·C 4 H 9 NO, (V), and 5‐methyl‐2‐thiouracil–melamine (3/2), 3C 5 H 6 N 2 OS·2C 3 H 6 N 6 , (VI). Synthon 3 s N·S;N·N;N·O was formed in three structures in which two‐dimensional hydrogen‐bonded networks are observed, while doubly hydrogen‐bonded interactions were formed instead in the remaining three cocrystals whereby three‐dimensional networks are preferred. As desired, the S atoms are involved in hydrogen‐bonding interactions in all six structures, thus illustrating the ability of sulfur to act as a hydrogen‐bond acceptor and, therefore, its value for application in crystal engineering.