Nitrophenyl ureas and amides

A second category of structures are solvates of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in which the dipolar solvent interferes with the urea tape synthon, e.g. PNPU-H, -CN, -Me, -CONH2, -COCH3. The solvent-O successfully 

X = 4-i (DMSO), 4-CONH2 (DMSO), 4-CH3 (DMSO), 4-COCH3 (DMSO) 

154°) [29], Urea molecules align along the short -axis (4.67 A) and the aryl groups are twisted out of the urea plane (45.4, 49.2°) to accommodate the hydrogen bonded tape. The p-ethynyl derivative is isomorphous and isostructural to the iodo structure, consistent with iodo-ethynyl exchange in crystal structures [30]. 

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