Selective encapsulation of lithium ion by the new azacage 5,12,17,trimethyl-1,5,9,12,17-penta-azabicyclo[7.5.5]nonadecane (L). Thermodynamic studies and crystal structures of the lithium complex [LiL][BPH4] and of the monoprotonated salt [HL][Cl]·(H2O)3

Abstract

Multinuclear n.m.r. and thermodynamic studies in aqueous solution indicate that the cage-like azamacrobicycle 5,12,17-trimethyl-1,5,9,12,17-penta-azabicyclo[7.5.5]nonadecane (L) is able to selectively encapsulate the lithium ion, forming a stable 1 : 1 complex (log k= 3.1, ΔH°=–2.1kJ mol^–1, ΔS°= 52.3 J mol^–1 K^–1); the crystal structures of the complex [LiL][BPh₄] and of the monoprotonated salt [HL][Cl]·3H₂O have been determined.