Nitrate Encapsulation within the Cavity of Polyazapyridinophane. Considerations on Nitrate−Pyridine Interactions

• Published in: Crystal growth & design Vol. 10; no. 8; pp. 3418 - 3423
• Main Authors: Valencia, Laura, Bastida, Rufina, García-España, Enrique, de Julián-Ortiz, J. Vicente, Llinares, José M, Macías, Alejandro, Pérez Lourido, Paulo
• Format: Journal Article
• Language: English
• Published: Washington,DC American Chemical Society 04-08-2010
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Encapsulation; Pyridine; Hydrogen bonds; Nitrates; Cyclophane; Macrocycle; Crystal structure
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg100111b

Interaction of nitrate anions with a cyclophane (L) containing two pyridine units connected to two diethylenetriamine bridges through methylene positions is reported both in pure water and in the solid state. The crystal structure of [H4 L](NO3)4 shows that one of the nitrate anions resides in the macrocyclic cavity forming two sets of bifurcated hydrogen bonds with the four protonated amino groups of the macrocycle. This anion is symmetrically placed in the middle of the pyridine rings with distances between its nitrogen atom and the centroids of the ring of 3.58 Å. Despite this location, calculations by theoretical analysis were carried out to confirm whether the stabilizing effect is due to anion−π interactions.