Conformational choice in disilver cryptates; an 1H NMR and structural study

Abstract

Disilver complexes of three iminocryptands, with either tris(aminopropylamine)- or tris(aminoethylamine)-derived caps {N[(CH₂)_nNCHRCHN(CH₂)_n]₃N (n = 2 or 3, R = 1,3-(CH₂)₂C₆H₄ or 2,5-(CH₂)₂C₄H₄O)} have been structurally characterised, and show relatively close approach of the silver(I) ions (3.08–3.77 Å). Differences in the geometry of the coordination site adopted can be related to the flexibility of the cryptand host. This is also important in solution, where the smaller cap-size cryptates are restricted to one conformation while the larger cap-size cryptates appear ready to adopt a range of conformations.