Molecular Cocrystals of Aromatic Carboxylic Acids with 1,1-Diethylurea: Synthesis and the Crystal Structures of a Series of Nitro-Substituted Analogues

Abstract

Molecular adducts of 1,1-diethylurea with the nitro-substituted aromatic carboxylic acids 2-nitrobenzoic acid, [(C7H5NO4)(C5H12N2O)] (1), 3-nitrobenzoic acid, [(C7H5NO4)(C5H12N2O)] (2), 4-nitrobenzoic acid, [(C7H5NO4)2(C5H12N2O)] (3), 3,5-dinitrobenzoic acid, [(C7H4N2O6)(C5H12N2O)] (4), 5-nitrosalicylic acid, [(C7H5NO5)(C5H12N2O)] (5) and 3,5-dinitrosalicylic acid, [(C7H4N2O7)(C5H12N2O)] (6), have been prepared and characterized by using infrared spectroscopy, and, in the case of four of these [(1), (4), (5) and (6)], by single-crystal X-ray diffraction methods. In all examples, primary cyclic hydrogen-bonding interactions are found between the amide group of the substituted urea and the carboxylic acid group of the acid, while further peripheral associations result predominantly in simple chain polymeric structures, and in one case [adduct (1)], a cyclic tetramer. The crystal structure of the parent 1,1-diethylurea has also been determined, revealing a cyclic hydrogen-bonded tetramer which forms into a chain polymer by weak hydrogen-bonding associations.