Self-assembled reversed bilayers directed by pnictogen bonding to form vesicles in solution

Abstract

Artificial vesicles can aid in the study and understanding of biological cell membranes. This study employs pnictogen bonding to actively direct the self-assembly of a true reversed bilayer. Antimony(iii) alkoxide cages that self-assemble through multiple strong SbO interactions propagate in two dimensions to form a reverse bilayer structure in the solid state. Long alkyl tails allow these reverse bilayers to be processed into vesicles in solution that are a reverse of biological cell membranes.

Self-assembly of reversed bilayer vesicles through pnictogen bonding: water-stable supramolecular nanocontainers for organic solvents

“…The Sb-Ch-C angles are signicantly more acute in Sb-1 Et ($102 ) than in alkoxide Sb-2 R ($118 ). 24,25 In the crystal structure, molecules of Sb-1 Et self-assemble through pnictogen bonds to form a reversed bilayer structure where each antimony interacts with three distinct sulphur atoms ( Fig. 4a).…”

“…This motif differs slightly from those observed with the antimony alkoxide cages, where every pnictogen bond is with a molecule in the opposing layer. 24,25 The ability of the thiol analogue to form a similar bilayer structure contrasts with Sb(S 2 C 6 H 4 )SMe which does not form a bilayer structure in the solid state whereas the oxygen analogue, Sb(O 2 C 6 H 4 )OMe, does. 34 This hints at the importance of the cage structure in promoting a predictable bilayer assembly.…”

“…Noncovalent interactions can be used to self-assemble reversed vesicles with more dynamic behaviour. Hydrogen bonding (HB) 22,23 and pnictogen bonding (PnB) 24 have also been successfully applied to this problem.…”

“…24,25 Sonication of crystalline Sb-2 NHCONon under strictly anhydrous conditions resulted in the formation of reversed bilayer vesicles with an average diameter of 70 nm. 24 These compounds represent a well-behaved model system that allows for careful study, but they are susceptible to hydrolysis at the Sb-O bonds. This imposes limits on the future application of these unique supramolecular structures.…”

Tweaking the Charge Transfer: Bonding Analysis of Bismuth(III) Complexes with a Flexidentate Phosphane Ligand

“…12 In the past few years, the potential of PnB in structural assembly, supramolecular architecture, anion sensing, (organo)catalysis, and molecular recognition has also been highlighted. 7 , 13 − 21 On the basis of thorough computational studies, 6 , 9 , 22 − 41 pnictogen bonding is chiefly electrostatic in nature (attraction between the oppositely charged regions around the two centers). Moreover, charge transfer effects (donation from the lone pair of the Lewis base into the σ*-antibonding orbitals at the pnictogen center) may also contribute, though to a much lesser extent.…”