Host-guest complexes of the Beer-Can-cryptand: prediction of ion selectivity by quantum chemical calculations XI

摘要

Based on DFT calculations (B3LYP/LANL2DZp) and the application of model equations, as well as a comparison of M-N-donor length with an unstrained reference ([M(solvent)(6)](n+)), the selectivity of the alkali and alkaline earth cations (Li+ - Cs+ and Be2+ - Ba2+) for the recently synthesized cryptand bis-triazacyclononane tris-pyridyl N-9-azacryptand (Beer-Can) was investigated. The host can bind the alkali cation K+ best, followed by the alkaline earth cations Ca2+ and Sr2+, and by Na+ and Ba2+. This selectivity pattern is identical to the selectivity of the Lehn-type cryptand [phen.phen.phen], which suggests a similar cavity size. The good flexibility of the Beer-Can is provided by the aza-crown-like top and bottom of the "can," and the pyridines on the "can-wall."