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Acetonitrile inclusion complexes of piperazine‐based macrocycles
Author(s) -
Huuskonen Juhani,
Rissanen Kari
Publication year - 1995
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.1995199509224
Subject(s) - acetonitrile , chemistry , piperazine , molecule , crystallography , inclusion compound , thermogravimetry , inorganic chemistry , organic chemistry
New piperazine‐based macrocycles with single small cavities were prepared by using high dilution technique. The inclusion of acetonitrile into the cavity ( 7, 8 ) or clathrate formation ( 3 ) was studied by 1 H‐NMR spectroscopy in solution and by X‐ray diffraction in the crystalline state. The cycle 3 forms a molecular cleft, a molecular pocket, where the acetonitrile molecule is held by four weak N…H interactions reinforcing the clathrate formation. The cycles 7 and 8 contain a rigid cavity for an exact sterical fit with the methyl group of a linear compound like acetonitrile. The acetonitrile inclusion complex with 7 proved to be stable under normal conditions and was studied by means of thermogravimetry. It is stable up to 80°C and the breakdown is complete when the temperature is raised over 120°C. Solid‐state IR studies show a shift of the cyano band of 5 cm −1 to smaller wave numbers when compared with free acetonitrile. The acetonitrile methyl group is shielded and in the 1 H‐NMR spectrum its signal is shifted to δ = 1.85.