TY - JOUR
T1 - Harnessing nonclassical hydrogen bonding in sulfur containing dynamic [2]rotaxanes
AU - Tritton, Daniel Nnaemaka
AU - Tang, Fung-Kit
AU - Kwan, Chak-Shing
AU - Low, Kam-Hung
AU - Ng, Maggie
AU - Chen, Aspen X.-Y.
AU - Ma, Kaikai
AU - Tang, Man-Chung
AU - Leung, Ken Cham-Fai
N1 - We acknowledge the financial support from Hong Kong Baptist University (RMGS-2022-13-07 and BHT-24-25-CHEM-01). C.-S. Kwan acknowledged the financial support from Great Bay University and Guangdong Province Pearl River Talent Plan Young Top Talents.
Publisher copyright:
© 2025 The Author(s). Published by Elsevier Ltd.
PY - 2026/1
Y1 - 2026/1
N2 - Mechanically interlocked molecules are a diverse set of compounds which have been vigorously studied in recent years, owning to their unique properties and topologies afforded by the presence of a mechanical bond(s). There are numerous elegant synthetic strategies available to chemists to prepare these types of compounds and, focussing on the preparation of rotaxanes, imine “clipping” is a commonly employed technique; non-covalent interactions between an alkylammonium moiety RNH2+R’ on a linear thread and donor atoms on a crown macrocycle govern the self-assembly of these. Though oxo-crowns are typically utilized, there is room for exploring thiacrown ethers which, despite garnishing less attention, can exhibit vastly different behaviours thanks to the “soft” sulfur atoms present. Bearing this in mind, three novel [2]rotaxanes with phenanthroline/pyridine sulfur containing crowns namely Rot-1, Rot-2 and Rot-3 have been synthesized by imine forming reactions, as well as their reduced amine counterparts Rot-1-red, Rot-2-red and Rot-3-red. X-ray crystal structures were obtained for the three imine rotaxanes and Rot-1-red, revealing π-stacking and notably two types of non-classical hydrogen-bonding: (1) [C–H⋯S] and (2) [C–H⋯F] bonds. When tested for metal ion binding capability, Rot-1, Rot-2 and Rot-3 showed 16-fold, 4-fold and 53-fold fluorescent “turn-on” with Pd2+, respectively, rendering Rot-3 selective towards the precious group metal. The highest response of Rot-3 was proposed to be due to exocyclic binding of Pd2+ disrupting essential non-classical H-bonds, leading to enhanced Lewis acid hydrolysis. Binding energies from density functional theory (DFT) with small difference between endocyclic/exocyclic configuration supported the proposed mechanism of enhanced emission response in Rot-3. This work showcases (i) the first examples of imine clipping rotaxanes adopting thiacrown macrocycles and (ii) how their structures may be elegantly tailored to become Pd2+ selective chemosensors, partially through modification of canonical/non-canonical H-bonding.
AB - Mechanically interlocked molecules are a diverse set of compounds which have been vigorously studied in recent years, owning to their unique properties and topologies afforded by the presence of a mechanical bond(s). There are numerous elegant synthetic strategies available to chemists to prepare these types of compounds and, focussing on the preparation of rotaxanes, imine “clipping” is a commonly employed technique; non-covalent interactions between an alkylammonium moiety RNH2+R’ on a linear thread and donor atoms on a crown macrocycle govern the self-assembly of these. Though oxo-crowns are typically utilized, there is room for exploring thiacrown ethers which, despite garnishing less attention, can exhibit vastly different behaviours thanks to the “soft” sulfur atoms present. Bearing this in mind, three novel [2]rotaxanes with phenanthroline/pyridine sulfur containing crowns namely Rot-1, Rot-2 and Rot-3 have been synthesized by imine forming reactions, as well as their reduced amine counterparts Rot-1-red, Rot-2-red and Rot-3-red. X-ray crystal structures were obtained for the three imine rotaxanes and Rot-1-red, revealing π-stacking and notably two types of non-classical hydrogen-bonding: (1) [C–H⋯S] and (2) [C–H⋯F] bonds. When tested for metal ion binding capability, Rot-1, Rot-2 and Rot-3 showed 16-fold, 4-fold and 53-fold fluorescent “turn-on” with Pd2+, respectively, rendering Rot-3 selective towards the precious group metal. The highest response of Rot-3 was proposed to be due to exocyclic binding of Pd2+ disrupting essential non-classical H-bonds, leading to enhanced Lewis acid hydrolysis. Binding energies from density functional theory (DFT) with small difference between endocyclic/exocyclic configuration supported the proposed mechanism of enhanced emission response in Rot-3. This work showcases (i) the first examples of imine clipping rotaxanes adopting thiacrown macrocycles and (ii) how their structures may be elegantly tailored to become Pd2+ selective chemosensors, partially through modification of canonical/non-canonical H-bonding.
KW - Dynamic imine clipping
KW - Thiacrown
KW - Nonclassical S/F–H bonding
KW - π‒stacking
KW - [2]rotaxanes
U2 - 10.1016/j.mtchem.2025.103295
DO - 10.1016/j.mtchem.2025.103295
M3 - Journal article
SN - 2468-5194
VL - 51
JO - Materials Today Chemistry
JF - Materials Today Chemistry
M1 - 103295
ER -
