Precise Steric Control over 2D versus 3D Self-Assembly of Antimony(III) Alkoxide Cages through Strong Secondary Bonding Interactions

Abstract

Antimony(III) alkoxide cages were designed as building blocks for predictable supramolecular self-assembly. Supramolecular synthons featuring two Sb···O secondary bonding interactions (SBIs), each SBI stronger than 30 kJ/mol, were used to drive the formation of the supramolecular architectures. Judicious choice of pendant groups provided predictable control over the formation of self-assembled 3D columnar helices, which crystallized with hollow morphologies, or a self-assembled 2D bilayer. The Sb-O stretching frequency provides a spectroscopic signature of Sb···O SBI formation.

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

“…antimony alkoxide cage which is isolated as a crystalline material with a helical columnar supramolecular structure. 25 Solid-state characterization of antimony thiolate bilayer X-ray quality single crystals of Sb-1 Et were obtained from the slow evaporation of a solution of Sb-1 Et following sonication in acetonitrile. XRD analysis revealed the anticipated cage structure with three Sb-S primary bonds with average bond distance of 2.444(7)Å as depicted in Fig.…”

“…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.…”

“…1). 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.…”

Structures and Chemical Bonding in Antimony(III) Bromide Complexes with Pyridine

“…[1] The uniquef eature of the pnictogen atom comparedt o halogen and chalcogen, is the possibility to form three pnictogen bonds, providinga dditional opportunities for the crystal engineering. [11,25,26] Antimony(III) halidesa nd organoantinomy derivativesa re classical amphoteric compounds, which find broad application in the coordination chemistry.T hese compounds utilize the lone pairs on Sb or halogena toms to act as Lewisb ases towards the transition metals and the main group elements. [27][28][29][30][31] Sb III can also accept the lone pairo fadonor ligand, acting as the Lewis acid.…”