Potassium Ion Solvated by the Cryptand
4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane
The cryptand has three chains bearing two oxygen atoms each. Each chain (-CH2CH2OCH2CH2OCH2CH2-) is tethered to a nitrogen atom. The nitrogens are tetrahedral with the lone pairs pointing inward toward the potassium cation. Measure the N-K distance. It is ~3.0Å. The sum of the van der Waal's radii for nitrogen (1.55Å) and potassium (2.75Å) is 4.30Å . Clearly, the two atoms are with in ligating distance. Similarly, O-K distance is less than the sum of the van der Waal's radii. Measure it. Noteworthy is the gauche arrangement of the oxygens in each chain.