Structural and spectroscopic studies on 3,5-dinitrosalicylic acid complexes of urotropine and dicyclohexylamine. A theoretical analysis of the structure of the complex anion

In the reaction between 3,5-dinitrosalicylic acid and urotropine, the proton of the phenolic group is transferred to a nitrogen atom of urotropine to form a hydrogen-bonded ion-paired [N···Ophenolate=2.777(4) ?] compound. An analogous reaction between the acid and dicyclohexylamine yields a centrosymmetric ion-paired dimer [N···Ophenolate=2.864(4), N···Ocarbonyl= 2.940(5) ?]. The structures of the two compounds are discussed in relation to their infrared spectral features. The structure of the anion is also investigated theoretically by geometry-optimization calculations.