SLIDE 1 Chirality transfer from gold nanocluster to adsorbate evidenced by vibrational circular dichroism
Igor Dolamic, Birte Varnholt & Thomas Burgi Departement de Chimie Physique, Universite´ de Gene`ve, 30 Quai Ernest-Ansermet, 1211 Gene`ve 4, Switzerland
- Nat. Commun. 2015, 6, 7117
KRISHNADAS 02-01-2016
SLIDE 2
- M. Zhu et al., J. Am. Chem. Soc. 2008, 130, 5883
Crystal structure of Au25(SR)18
Ih Oh D5h
Gas phase structures of M12 clusters
- X. Li et al., Angew. Chem. Int. Ed. 2002, 41, 4786
SLIDE 3 Manzhou Zhu et al., Nano Lett. 2011, 11, 3963–3969
- E. S. Shibu, T. Pradeep Nano Lett. 2011, 11, 3963–3969
*
SLIDE 4
Igor Dolamic, Stefan Knoppe, Amala Dass & Thomas Bürgi Nat. Comm. 2012, 3, 798. 2-PET 1-PET
SLIDE 5
Schematic conformation on the dimeric motif (top to bottom): (a) cis−trans; (b) trans−trans
SLIDE 6
Runhai Ouyang and De-en Jiang J. Phys. Chem. C 2015, 119, 21555−21560 Schematic of the S−Au−S cis/trans, S−C anti/gauche, and C−C anti/gauche conformations
SLIDE 7 Bonds relevant for the discussion of the 2-PETconformation are marked (S–C1–C2–C3–C4) Centre 2-PET molecule adopts an anti conformation around the C1–C2 bond, whereas the other two molecules are in gauche conformation. Colour code: core Au atoms:
- range, staple Au atoms: ochre,
sulfur: green, carbon: blue, hydrogen: grey.
SLIDE 8
gauche gauche anti anti
CH2 wagging (1232 cm-1) CH2 wagging (1280 cm-1)
Infrared spectra of 2-phenylethylthiol and of gold cluster
2-PET
In-plane phenyl ring (1603, 1583 and 1495 cm-1) CH2 scissoring (1429, 1454 cm-1) In-plane phenyl C-H (1322 cm-1)
SLIDE 9
Infrared spectra of Au38(2-PET)24 and HPLC chromatogrammes of Au38(2-PET)24 enantiomers
SLIDE 10
Infrared and VCD spectra of Au38(2-PET)24
In plane phenyl ring vibrations (1495 cm-1) pure CH2 scissoring (1418 cm-1) CH2 scissoring + in-plane phenyl ring (1454 cm-1) CH2 wagging and twisting (1263 cm-1)
SLIDE 11
c d a b
SLIDE 12
VCD spectra of calculated structures
SLIDE 13
SLIDE 14
Comparison between experimental and calculated VCD spectra
SLIDE 15
SLIDE 16
Summary and Conclusions
VCD measurements reveal a chirality transfer from an intrinsically chiral metal
particle or cluster to the adsorbed achiral molecules. This is the first direct observation of chirality transfer of this kind. Interestingly, in coordination chemistry organic ligands with defined configuration are used to transfer the chiral information to the metal centre. In the system studied here it is in contrast the metal particle that transfers chirality to the organic molecule.
SLIDE 17
Further aspects
What is the role of the conformations of the ligands in the isomerism of monolayer
protected clusters? Isomers of Au25-xAgx(SR)18 and Ag25-xAux(SR)18 and optically active isomers among them? Will a chiral thiol induce a chiral geometry for otherwise achiral cluster core?
THANK YOU
