Intramolecular C-H...pi interactions influence the conformation of N,N'-dibenzyl-4,13-diaza-18-crown-6 molecules

摘要

Interaction of La(NO_3)_3 ·6H_2O, Eu(NO_3)_3·6H_2O, UO_2(NO_3)_2·6H_2O or hydrobromic acid with N,N'-dibenzyl-4,13-diaza-18-crown-6 leads to double protonation of the N-containing heterocycle, affording [(H~+)_2N,N'-dibenzyl-4,13-diaza-18-crown-6][La(NO_3)_5(H_2O)] (1), [(H~+)_2 N,N'-dibenzyl-4,13-diaza-18-crown-6] [Eu(NO_3)_5(H_2O)] (2), [(H~+)_2N,N'-dibenzyl-4,13-diaza-18-crown-6] [(mu-OH)_2{uo_2(no_3)_2}_2] (3) and (H_9O_4~+)_2[(H~+)_2N,N'-dibenzyl-4,13-diaza-18-crown-6]Br_4(5). The X-ray crystal structures of each compound were obtained, revealing unusual C-H...pi interactions between the phenyl substituents and two macrocyclic methylene protons that govern the overall conformation of the macrocycle. We also report the X-ray crystal structure of the rela5ted [(H_2O)_2(H~+)_2N,N'-dibenzyl-4,13-diaza-18-crown-6] [UO_2Cl_4] (4), which surprisingly, does not have the same conformation of the cation, rather, two molecules of water bind to the inner cavity of the crown ether.