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Unusual Encapsulation of Two Anions in the Cavity of Neutral Macrocyclic Octalactam, Preliminary Communication
Author(s) -
Szumna Agnieszka,
Jurczak Janusz
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20011219)84:12<3760::aid-hlca3760>3.0.co;2-y
Subject(s) - chemistry , dimer , crystallography , molecule , ion , stereochemistry , planar , organic chemistry , computer science , computer graphics (images)
A new neutral anion receptor – macrocyclic octalactam 2 , possessing a large 36‐membered ring, was synthesized, and its unusual property of encapsulation of two Cl − ions and two H 2 O molecules in the cavity was confirmed by X‐ray crystallography (see Figure ). The octalactam, consisting of four 2,6‐dicarbamoylpyridine and four ethylene moieties, exhibits a symmetrical, fully expanded conformation in the complex [(Cl) 2 ( 2 )(H 2 O) 2 ] 2− (obtained as 2 ⋅2 Bu 4 NCl⋅4 H 2 O⋅2 CH 2 Cl 2 ). Inside the cavity, encapsulated species – two Cl − ions and two H 2 O molecules – are connected to each other by H‐bonds. This kind of complex‐in‐complex system is formed by means of twenty intra‐ring H‐bonds and additionally four from the ‘outside' H 2 O molecules. Considering size and symmetry, it can be stated that the planar (H 2 O⋅Cl − ) 2 dimer fits well into the cavity of octalactam 2 . The ligand has an optimal arrangement of binding sites to form H‐bonds to every corner of the dimer.