Structure, Stability and Guest Affinity of Tris(3‐ureidobenzyl)amine Capsules in Solution

Abstract

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.

Novel Capsular Aggregates from Flexible Tripodal Triureas with Cs Symmetry

“…Previously, we demonstrated that dimeric aggregates 2·2 are excellent containers for MeI, CH 2 Cl 2 and MeNO 2 . [22] At À15 8C, the (Figure 8, left), which indicates that the presence of these guests inside the cavity may not influence the regioselectivity of the self-assembly process. [27] Interestingly, the spectra reveal two different resonances for MeI and MeNO 2 inside 5 a·5 a, with slightly different chemical shifts in a 2:1 ratio (Figure 8 a and 8 c, right).…”

“…Whereas the spectrum of 5 c is too complex to extract any conclusion, the 1 H NMR spectra of 5 a-b show typical signatures of tribenzylamine-derived capsules ( Figure 6). [21,22] Large shifts to lower frequencies were observed for the signals of the protons of the pendant aromatic substituents as well as the protons located at the C2 position of the tribenzylamine skeleton (labelled in Scheme 2), the latter shifted as much as 2 ppm to lower frequencies. Thus, whereas protons at C2 resonate at 7.5 ppm in [D 6 ]DMSO, they appear as broad signals at 5.7-5.9 ppm in the halogenated solvent.…”

“…Figure 1) form dimeric aggregates with cavities that are able to encapsulate guests of appropriate shape and size. [21,22] The resemblance of the spectra of triureas 5 with those of triureas 2 in CDCl 3 suggests the presence of capsules 5·5@CDCl 3 . Previously, we demonstrated that dimeric aggregates 2·2 are excellent containers for MeI, CH 2 Cl 2 and MeNO 2 .…”

“…[18] Whereas assemblies 1·1 exist as solvent-free capsular aggregates, [19,20] assemblies 2·2 are able to encapsulate guests of appropriate size and shape. [21,22] The tribenzylamine core provides a high degree of flexibility to triureas 1 and 2, which adopt averaged C 3v symmetry in competitive solvents with hydrogen bonds. In non-competitive solvents, aggreAbstract: Tris(2-and 3-ureidobenzyl)-A C H T U N G T R E N N U N G amines with C s symmetry self-assemble in solution forming mixtures of regioisomeric capsular aggregates, one of which is chiral and the other centrosymmetric.…”

Polyamide model compound containing the urea group as selective colorimetric sensing probe towards aromatic diamines

“…to give clathrates -opens the door to specific interactions with neutral molecules in the field of molecular recognition, or host-guest chemistry [33][34][35]. Moreover, aromatic urea derivatives have shown the ability to form oligomeric assemblies, or capsules, in which guests can be encapsulated in solution, and the complex capsules persist even in the solid state, as demonstrated by X-ray analysis [36][37][38]. solution.…”