U-Shaped Aromatic Ureadicarboxylic Acids as Versatile Building Blocks: Construction of Ladder and Zigzag Networks and Channels

In order to examine versatility of ureadicarboxylic acids as U-shaped building blocks for crystal engineering, their crystal structures and cocrystals with pyridine derivatives were investigated. H-bonding networks created by a sequential linking of H-bonded carboxylic acid dimers resulted in the formation of ladder-type networks in the crystals of N,N′-diethyl-N,N′-diphenylureadicarboxylic acid (2) and N,N′-diallyl-N,N′-diphenylureadicarboxylic acid (3). A zigzag type H-bonding network with wedging of water molecules into carboxy–carboxy H-bonding was observed for N,N′-dibenzyl-N,N′-diphenylureadicarboxylic acid (4). Cocrystals of N,N′-dimethyl-N,N′-diphenylureadicarboxylic acid (1) with 2,5-di(pyridine-4-yl)thiazolo[5,4-d]thiazole (5) and 2 with 4,4′-dipyridyl (6) afforded zigzag-type assembled structures. Two types of channel structures were created in the cocrystals of 1 and dipyridylurea (7) by inclusion of water molecules together with either methanol or ethanol. The former afforded a straight-type one-dimensional channel, while the latter afforded a fishnet-type two-dimensional channel.