An official website of the United States government
Pnictogen bonding is beginning to emerge as a useful supramolecular interaction. The design strategies for these systems are still in the early stages of development and much attention has been focused on the lighter pnictogens. Pnictogen bond donors can have up to three independent sites for binding which can result in triple pnictogen bonding. This has been observed in the self-assembly of antimony alkoxide cages, but not with the lighter congeners. This work reports structural characterization of an analogous arsenic alkoxide cage that engages in a single pnictogen bond and synthetic explorations of the bismuth congener. DFT calculations are used to evaluate the differences between the structures. Ultimately the partial charge on the pnictogen and the energy of the pnictogen lone pair dictate the strength, orientation and number of pnictogen bonds that these cages form. Antimony cages strike the best balance between strength and directionality, allowing them to achieve triple pnictogen bonding where the other congeners do not.
more »
« less
The complicating role of pnictogen bond formation in the solution-phase and solid-state structures of the heavier pnictogen atranes
The structure of the simplest stibatrane has been a mystery since it was first prepared in 1966. This study reports the preparation and characterization of two stibatranes from triethanolamine and triisopropanolamine. Solid state structures reveal macrocycles that contain favourable inter- and intramolecular pnictogen bonds. Solution studies, corroborated by DFT analysis, reveal an equilibrium mixture assigned to monomer and pnictogen-bonded dimer. This allowed for the determination of an enthalpy associated with pnictogen bond formation of −27 kJ mol −1 , in line with the supramolecular nature of these interactions.
more »
« less
- Award ID(s):
- 1847878
- PAR ID:
- 10410204
- Date Published:
- Journal Name:
- Dalton Transactions
- Volume:
- 51
- Issue:
- 30
- ISSN:
- 1477-9226
- Page Range / eLocation ID:
- 11335 to 11339
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Stabilizing nitrogen pnictogen bond interactions were measured using molecular rotors. Intramolecular C=O⋅⋅⋅N interactions were formed in the bond rotation transition states which lowered the rotational barriers and increased the rates of rotation, as measured by EXSY NMR. The pnictogen interaction energies show a very strong correlation with the positive electrostatic potential on nitrogen, which was consistent with a strong electrostatic component. In contrast, the NBO perturbation and pyramidalization analyses show no correlation, suggesting that the orbital‐orbital component is minor. The strongest C=O⋅⋅⋅N pnictogen interactions were comparable to C=O⋅⋅⋅C=O interactions and were stronger than C=O⋅⋅⋅Ph interactions, when measured using the sameN‐phenylimide rotor system. The ability of the nitrogen pnictogen interactions to stabilize transition states and enhance kinetic processes demonstrates their potential in catalysis and reaction design.more » « less
-
Abstract Our interest in the design of heavy pnictogen‐based Lewis acids for anion trafficking across biological membrane mimics has led us to investigate trivalent bismuthenium cations as chloride anion transporters. Here, we describe two chlorodiarylbismuthines, elaborated on aperi‐substituted naphthalene backbone and stabilized by an adjacent thio‐ or seleno‐ether functionality that engages the bismuth center in a Ch→Bi interaction (Ch=chalcogen). These new derivatives are stable in aqueous environment and readiliy transport chloride anions across the membrane of phospholipid‐based vesicles loaded with KCl. In addition to establishing the use of such motifs in anion transport, this investigation shows that the Lewis acidity, lipophilicity, and thus chloride transport properties depend on the nature of the chalcogen.more » « less
-
The solution phase anion binding behavior of a water-stable bidentate pnictogen bond donor was studied. A modest change in the visible absorption spectrum allowed for the determination of the binding constants. High binding constants were observed with cyanide, cyanate, and acetate, and these were corroborated with density functional theory (DFT) calculations. The receptor could be recovered free from the anion following treatment with methyl triflate, confirming that it remains intact. The tight binding of cyanide and water stability were exploited to use this system as a supramolecular catalyst in a phase-transfer Strecker reaction, further demonstrating the utility of pnictogen bonding as a tool in noncovalent catalysis.more » « less
-
New routes to the formation of macrocyclic molecules are of high interest to the supramolecular chemistry community and the chemistry community at large. Here we describe the incorporation of heterocyclic core units into discrete macrocycles via the utilization of a pnictogen-assisted self-assembly technique. This method allows for the rapid and efficient formation of discreet macrocyclic units from simple dithiol precursors in high yields with good control over macrocycle size. Up to this point, this technique has been reported on primarily benzylic thiol systems with very little incorporation of endohedral heteroatoms in the resulting assemblies. This study demonstrates the effective incorporation of heterocyclic core molecules allowing for the formation of a more functional cavity, resulting in the formation and crystallization of novel furan- and thiophene-based disulfide dimer and trimer macrocycles, respectively, that are isolated from a range of other larger discrete macrocycles that assemble as well. These disulfide macrocycles can be trapped as their more kinetically stable thioether congeners upon sulfur extrusion.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2DT01377K
