Molecular Cocrystals of Carboxylic Acids. XXVIII. Nitro-Substituted Carboxylic Acids with Lewis Bases: the Crystal Structures of the Adducts of 3,5-Dinitrobenzoic Acid with N-Methylaniline (1 : 1), (4-Nitrophenyl)acetic Acid with Cyclohexane-1,4-diamine (2 : 1), and 5-Nitrosalicylic Acid with 2-Imidazolidone (2 : 1)

Abstract

A number of molecular adducts of nitro-substituted aromatic acids with Lewis bases have been prepared and characterized by infrared spectroscopy and in three cases by X-ray diffraction methods. These three compounds are the adducts of: 3,5-dinitrobenzoic acid (dnba) with N-methylaniline (nma), [(dnba)^-(nma)⁺] (1); (4-nitrophenyl)acetic acid (4-npa) with cyclohexane-1,4-diamine (dach), [(4-npa)₂^2-(dach)²⁺] (4); 5-nitrosalicylic acid (5-nsa) with 2-imidazolidone (idaz), [(5-nsa)₂(idaz)] (5). Other compounds are the adducts of 3,5-dinitrobenzoic acid with 2,6-dimethylpyridine (dmp), [(dnba)(dnba)^-(dmp)⁺] (2), and with 1-methylpyrrole-2-carboxylic acid (cmp), [(dnba)^-(cmp)⁺] (3). Compounds (1) and (3) have 1 : 1 stoichiometry, while (2), (4) and (5) are 2 : 1 adducts. Proton transfer occurs in most examples [complex (5) is the exception].