Substituent effects control the self-association of molecular clips in the crystalline state.
We report the X-ray crystal structure of 11 molecular clips and analyze the influence of substituents (e.g., OMe, Me, and NO2) and their location on the observed crystal packing. Molecular clips 3a and 3b form tapelike structures in the crystal due to pi-pi interactions between the aromatic walls. Compounds 3d, 3eC, and 3fC form dimers driven by critical C-H...O interactions and then form tapes driven by pi-pi interactions in the crystal. These two building motifs, pi-pi and C-H...O interactions, can be used to rationalize the enantio- and diastereoselectivity observed in the X-ray crystal structures of the remaining five molecular clips. For example, the C-H...O interactions are found to dictate the formation of homochiral dimers in the structures of (+/-)-3eT and (+/-)-3fT and to control the diastereoselective formation of 6a2-6c2 dimeric motifs with internal p-dimethoxy-o-xylylene walls. Overall, the results suggest that substituent effects that induce even weak intermolecular interactions (e.g., C-H...O) can be used to reliably control crystal packing within glycoluril-based systems.
Wang
Zhi-Guo
ZG
Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, 430079, PRC.
Zhou
Bao-Han
BH
Chen
Yun-Feng
YF
Yin
Guo-Dong
GD
Li
Yi-Tao
YT
Wu
An-Xin
AX
Isaacs
Lyle
L
D000480:Alkynes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D019281:Dimerization; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D006574:Heterocyclic Compounds, 2-Ring; D048289:Imidazolidines
D000480:Alkynes; D007093:Imidazoles; C092018:glycoluril; D006574:Heterocyclic Compounds, 2-Ring; D048289:Imidazolidines