Chirality transfer from gold nanocluster to adsorbate evidenced by - PowerPoint PPT Presentation

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

Gas phase structures of M 12 clusters O h D 5h I h X. Li et al ., Angew. Chem. Int. Ed. 2002, 41 , 4786 Crystal structure of Au 25 (SR) 18 M. Zhu et al ., J. Am. Chem. Soc. 2008, 130 , 5883

* Manzhou Zhu et al., Nano Lett. 2011, 11, 3963–3969 E. S. Shibu, T. Pradeep Nano Lett. 2011, 11, 3963–3969

2-PET 1-PET Igor Dolamic, Stefan Knoppe, Amala Dass & Thomas Bürgi Nat. Comm. 2012, 3, 798.

Schematic conformation on the dimeric motif (top to bottom): (a) cis−trans; (b) trans−trans

Schematic of the S−Au−S cis/trans, S−C anti/gauche, and C−C anti/gauche conformations Runhai Ouyang and De-en Jiang J. Phys. Chem. C 2015, 119, 21555−21560

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: orange, staple Au atoms: ochre, sulfur: green, carbon: blue, hydrogen: grey.

Infrared spectra of 2-phenylethylthiol and of gold cluster 2-PET anti gauche CH 2 wagging (1232 cm -1 ) anti CH 2 wagging (1280 cm -1 ) gauche CH2 scissoring (1429, 1454 cm -1 ) In-plane phenyl ring (1603, 1583 and 1495 cm -1 ) In-plane phenyl C-H (1322 cm -1 )

Infrared spectra of Au 38 (2-PET) 24 and HPLC chromatogrammes of Au 38 (2-PET) 24 enantiomers

Infrared and VCD spectra of Au 38 (2-PET) 24 CH 2 wagging and twisting (1263 cm -1 ) In plane phenyl ring vibrations (1495 cm -1 ) pure CH 2 scissoring (1418 cm -1 ) CH 2 scissoring + in-plane phenyl ring (1454 cm -1 )

c d a b

VCD spectra of calculated structures

Comparison between experimental and calculated VCD spectra

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.

Further aspects  What is the role of the conformations of the ligands in the isomerism of monolayer protected clusters?  Isomers of Au 25-x Ag x (SR) 18 and Ag 25-x Au x (SR) 18 and optically active isomers among them?  Will a chiral thiol induce a chiral geometry for otherwise achiral cluster core? THANK YOU