Substituent Effects Control the Self-Association of Molecular Clips in the Crystalline State

Abstract

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.

Cucurbit[n]urils (n= 5–8): A Comprehensive Solid State Study

“…22 It has also been shown that they can play a critical role in molecular crystals containing glycoluril derivatives. 44,45 Moreover, Kim et al pointed out the importance of numerous CH 333 O hydrogen bonds in CB [7] condensed phases with regard to its gelation behavior in acidified water. 22 Therefore, the present work demonstrates the importance of such interactions in the main representatives of the CB[n] family.…”

Synthesis and Self‐Aggregation of Enantiopure and Racemic Molecular Tweezers Based on the Bicyclo[3.3.1]nonane Framework

“…[4,5] However, to make a distinction might seem to be a little superfluous because the recognition event occurs in a more or less shallow cleft for both types of receptors. Molecular tweezers can in principle be divided into three groups: semirigid, [6][7][8][9][10][11][12][13] conformationally labile, [2,[14][15][16][17][18][19][20] and conformationally controlled by hydrogen bonds or metal chelation. [21][22][23] The interaction that mediates the recognition process can, in addition to London dispersion forces, be based on hydrogen-bonding, [24] charge-transfer, [14] ion-p, [8,25] p-p, [1] electrostatic, [8] and coupled interactions.…”

Synthesis and Alkali Metal Picrate Extraction Capabilities of Novel Bis(benzocrown Ether)s Based on Diphenylglycoluril

“…[12][13][14][15][16] Наиболее часто для этих целей используют диэфир 1, который легко получается при конденсации дифенилгликольурила с формальдегидом с образова-нием тетракис(гидроксиметил)дифенилгликольурила и его последующей дегидратации. [19] За исключением взаимодействия с гидрохиноном, уреидоалкилирова-ние других производных бензола с участием эфира 1 осложнено длительным временем реакции и умеренны-ми выходами продуктов.…”

“…На основе его тетракис-производных получено много U-образных молеку-лярных рецепторов, так называемых молекулярных клипсов, в которых арильные заместители имеют син-конфигурацию. [12][13][14][15][16] Эти данные, а также результаты компьютерного молекулярного моделирования позво-лили нам предположить, что бис(бензокраун-эфиры) должны иметь конфигурацию краун-эфирных циклов благоприятную для образования устойчивых сэндви-чеподобных комплексов.…”