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 proto n of the phenolic group is transferred to a nitrogen atom of urotropine to form a hydrogen-bonded ion-paired [N...O-phenolate = 2.777(4) Angstrom] com pound. An analogous reaction between the acid and dicyclohexylamine yields a centrosymmetric ion-paired dimer [N...O-phenolate = 2.864(4), N...O-carbo nyl = 2.940(5) Angstrom]. The structures of the two compounds are discussed in relation to their infrared spectral features. The structure of the anio n is also investigated theoretically by geometry-optimization calculations. (C) 2001 Elsevier Science B.V. All rights reserved.