Separation of Enantiomers and CD Spectra of Au40(SCH2CH2Ph)24: Spectroscopic Evidence for Intrinsic Chirality

Knoppe, Stefan; Dolamic, Igor; Dass, Amala; Bürgi, Thomas

doi:10.1002/anie.201202369

Cited by 145 publications

(150 citation statements)

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Section: Resultsunclassified

Nonlinear Optical Properties of Thiolate-Protected Gold Clusters

et al. 2015

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Thiolate-protected gold clusters are promising candidates for imaging applications due to their interesting, size-dependent properties. Their high stability and the ability to functionalize the clusters with biocompatible ligands render the clusters for various imaging techniques such as fluorescence microscopy or Second-Harmonic Generation microscopy. The latter nonlinear optical effect has not yet been observed on this type of ultra-small nanoparticles.We hereby present Second-and Third-Harmonic Generation and multi-photon luminescence of two thiolate-protected gold clusters, Au 25 (SCH 2 CH 2 Ph) 18 and Au 38 (SCH 2 CH 2 Ph) 24 . At a fundamental wavelength of 800 nm, the Au 38 (SCH 2 CH 2 Ph) 24 cluster is active. In contrast, Au 25 (SCH 2 CH 2 Ph) 18 does not yield significant SHG signal. We ascribe this to the center of inversion in the Au 25 cluster. Measurements on chiral Au 25 (capt) 18 (capt: captopril) gave an SHG response, supporting this interpretation. We also observed Third-Harmonic Generation at a fundamental wavelength of 1200 nm. At 800 and 1,100 nm, the clusters decompose after short illumination time, but are stable at illumination at 1,200 nm. This may be exploited in combined deep tissue imaging and photothermal heating for theranostics applications.

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Section: Resultsunclassified

Nonlinear Optical Properties of Thiolate-Protected Gold Clusters

et al. 2015

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“…Recent studies furthermore showed even longer staples such as Au 3 (SR) 4 , 2 Au 4 (SR) 5 3 or Au 5 (SR) 6 . Particularly stable clusters were found to be Au 25 (SR) 18 , 5,6 Au 38 (SR) 24 , 7 Au 40 (SR) 24 , 8,9 Au 102 (SR) 44 , 10 and Au 144 (SR) 60 , 11 although later a large number of stable clusters has been found (see examples in ref. Particularly stable clusters were found to be Au 25 (SR) 18 , 5,6 Au 38 (SR) 24 , 7 Au 40 (SR) 24 , 8,9 Au 102 (SR) 44 , 10 and Au 144 (SR) 60 , 11 although later a large number of stable clusters has been found (see examples in ref.…”

Section: Introductionmentioning

confidence: 99%

Pd₂Au₃₆(SR)₂₄cluster: structure studies

Bei

Kaziz

et al. 2015

Nanoscale

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The location of the Pd atoms in Pd2Au36(SC2H4Ph)24, is studied both experimentally and theoretically. X-ray photoelectron spectroscopy (XPS) indicates oxidized Pd atoms. Palladium K-edge extended X-ray absorption fine-structure (EXAFS) data clearly show Pd-S bonds, which is supported by far infrared spectroscopy and by comparing theoretical EXAFS spectra in R space and circular dichroism spectra of the staple, surface and core doped structures with experimental spectra.

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“…Currently, ac ouple of enantioseparation methods,i ncluding chiralcounterion-induced resolution [12] and chiral liquid chromatography [13] have been employed to obtain the nanocluster enantiomers.H owever,o wing to the shielding effect of the achiral phosphine ligands of Au 20 ,b oth methods are ineffective in separating Au 20 ( Figure S2 and S3). Currently, ac ouple of enantioseparation methods,i ncluding chiralcounterion-induced resolution [12] and chiral liquid chromatography [13] have been employed to obtain the nanocluster enantiomers.H owever,o wing to the shielding effect of the achiral phosphine ligands of Au 20 ,b oth methods are ineffective in separating Au 20 ( Figure S2 and S3).…”

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Enantioseparation of Au₂₀(PP₃)₄Cl₄ Clusters with Intrinsically Chiral Cores

et al. 2018

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Au (PP ) Cl (PP =tris(2-(diphenylphosphino)ethyl) phosphine), abbreviated as Au , is the only Au nanocluster with an intrinsically chiral core without a chiral environment (chiral ligands or Au-thiolate staples), making it a unique object to understand chiral evolution and explore chiral applications. Unfortunately, the synthesized Au is racemic, and its enantiomers have not yet been separated. Herein, we report a supramolecular assembly strategy with α-cyclodextrin (α-CD) to afford enantiopure Au in bulk, and an enantiomer excess (ee) value of as-separated Au of 97 %. As a result of its high purity, the distinctive optical activity of Au , which originates from electronic transitions confined in chiral cores, is fully explored. Theoretical studies reveals that the enantioseparation results from the preferential self-assembly of α-CD with organic ligands on the surface of right-handed Au .

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Separation of Enantiomers and CD Spectra of Au₄₀(SCH₂CH₂Ph)₂₄: Spectroscopic Evidence for Intrinsic Chirality

Abstract: Chirality unveiled: Thiolate-protected Au40(SR)24 clusters were enantioenriched using an HPLC approach. CD spectra show strong mirror-image responses, indicating the intrinsic chirality of a cluster of unknown structure protected with achiral ligands

Cited by 145 publications

References 35 publications

Nonlinear Optical Properties of Thiolate-Protected Gold Clusters

Nonlinear Optical Properties of Thiolate-Protected Gold Clusters

Pd₂Au₃₆(SR)₂₄cluster: structure studies

Enantioseparation of Au₂₀(PP₃)₄Cl₄ Clusters with Intrinsically Chiral Cores

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Separation of Enantiomers and CD Spectra of Au40(SCH2CH2Ph)24: Spectroscopic Evidence for Intrinsic Chirality

Abstract: Chirality unveiled: Thiolate-protected Au40(SR)24 clusters were enantioenriched using an HPLC approach. CD spectra show strong mirror-image responses, indicating the intrinsic chirality of a cluster of unknown structure protected with achiral ligands

Cited by 145 publications

References 35 publications

Nonlinear Optical Properties of Thiolate-Protected Gold Clusters

Nonlinear Optical Properties of Thiolate-Protected Gold Clusters

Pd2Au36(SR)24cluster: structure studies

Enantioseparation of Au20(PP3)4Cl4 Clusters with Intrinsically Chiral Cores

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Separation of Enantiomers and CD Spectra of Au₄₀(SCH₂CH₂Ph)₂₄: Spectroscopic Evidence for Intrinsic Chirality

Pd₂Au₃₆(SR)₂₄cluster: structure studies

Enantioseparation of Au₂₀(PP₃)₄Cl₄ Clusters with Intrinsically Chiral Cores