Three preorganized metallomacrocycles (9a-c) have been prepared with an immobilized uranyl cation (UO22 +) as an electrophilic center. The macrocyclization in MeOH was accomplished starting from the dialdehyde 7 and the diamines 11a-c using Ba2 + as template ion. Subsequently the Ba2 + complexes 8a-c were reacted with 1 equiv of UO2(OAc)2 to give the uranyl complexes 9a-c in 70 -80 % yield. The association constants of the complexes 9a-c with ammonia, benzylamine, and n-propylamine, determined by 1H NMR spectroscopy in CDCl3, range from 20 to 990 1· mol-1. The highest selectivity for ammonia was observed for 9b (Kass(NH3):Kass (BnNH2) = 33). Molecular mechanics calculations., performed using Quanta/CHARMm, predict that the substitution of the complexed water molecule in the uranyl complex 9a by ammonia is thermodynamically the most favorable.
van Veggel, F. C. J. M., Chiosis, G., Cameron, B. R., & Reinhoudt, D. (1995). Preorganized metallomacrocycles: selective receptor for NH@3#. Supramolecular chemistry, 4(4), 177-183. https://doi.org/10.1080/10610279408029470