Insights into Racemization of Metal Nanoclusters and Strategic Spontaneous Resolution.
basic_science · Level V
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- Record sourced from PubMed, PMID 41730519.
- Also identified by DOI 10.1021/acsnano.5c22337.
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Abstract
Chiral metal nanoclusters stand as pivotal materials in contemporary scientific research, yet their enantiomers predominantly crystallize as racemic mixtures, posing substantial challenges for chirality-based applications. This study elucidates the racemization mechanism in metal nanoclusters and proposes a rational strategy for achieving spontaneous resolution. We demonstrate that racemic cluster assemblies are stabilized in the unit cell by intermolecular interactions between opposite enantiomers; eliminating or diminishing these interactions induces spontaneous resolution, yielding homochiral crystals of either enantiomer. Two illustrative cases are presented: the racemic assembly of Cu<sub>25</sub>H<sub>10</sub>(PhFS)<sub>18</sub>(PPh<sub>4</sub>)<sub>3</sub> (PhFS = 2-fluorobenzenethiolate) is stabilized by extensive C-H···F hydrogen bonds between enantiomers. Removing fluorine substituents to form Cu<sub>25</sub>H<sub>10</sub>(PhS)<sub>18</sub>(PPh<sub>4</sub>)<sub>3</sub> (PhS = benzenethiolate) disrupts these interactions and enables resolution. In Cu<sub>4</sub>(PhS)<sub>6</sub>(PPh<sub>4</sub>)<sub>2</sub>, substituting benzene with thiophene ligands (forming R/S-Cu<sub>4</sub>(ThS)<sub>6</sub>(PPh<sub>4</sub>)<sub>2</sub>, ThSH = 2-thiophenethiol) diminishes C-H···π interactions between enantiomers, facilitating spontaneous resolution. Successful resolution is unambiguously confirmed by mirror-image circular dichroism spectra of enantiopure crystals. This study demonstrates the critical role of intermolecular interactions in racemate formation and presents strategies for achieving spontaneous chiral resolution in metal nanoclusters.