Structure, stability and guest affinity of tris(3-ureidobenzyl)amine capsules in solution.
In non-competitive solvents, the tris(3-ureidobenzyl)amines 1 a-c form dimeric assemblies in which guests such as CH(3)CN, CH(3)NO(2), CH(2)Cl(2), CH(3)I, CH(2)BrCl, CH(2)Br(2), CHCl(3) and C(6)H(6) can be encapsulated. Variable temperature (1)H and (1)H,(1)H-ROESY NMR spectroscopy, as well as pulsed-gradient spin-echo (PGSE) diffusion measurements were used to investigate the encapsulation within 1 a1 a (1 a: tris{3-[N'-(4-butylphenyl)ureido]benzyl}amine). Kinetic parameters for the encapsulation of CH(3)NO(2), CH(2)Cl(2) and CH(3)I, both in CDCl(3) and in [D(8)]toluene have been obtained by using magnetisation transfer methods. These data are discussed together with the thermodynamic parameters. The affinity between guest and capsule seems to be dictated mainly by the electronic, size and shape complementarity between cavity and guest. A gating mechanism for guest exchange is proposed.
Alajarín
Mateo
M
Departamento de Química Orgánica, Facultad de Química, Universidad de Murcia, Campus de Espinardo, Murcia-30100, Spain.
Pastor
Aurelia
A
Orenes
Raúl-Angel
RA
Martínez-Viviente
Eloísa
E
Rüegger
Heinz
H
Pregosin
Paul S
PS