The way to prepare gold clusters - Every atom makes a difference

Июль 31, 2022

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The way to prepare gold clusters - Every atom makes a difference

Содержание

2. The strategy for preparing metal clusters Bottom-up preparation Metal ions – electrostatic repulsion ↓ reduction Neutral
3. “Magic numbers” for bare gold clusters Katakuse, I. et al. Int. J. Mass Spec. Ion Proc.
4. Protection of metal clusters by ligands I. Protection by phosphine ligands Dative ligands Au11(PPh3)7(SCN)3 (8e-, magic
5. Protection of metal clusters by ligands I. Protection by phosphine ligands Chiral clusters with BINAP [Au11(BINAP)4Br2]+
6. Protection of metal clusters by ligands II. Protection by thiolate ligands – high affinity between Au
7. Protection of metal clusters by ligands II. Protection by thiolate ligands “Brust-Schiffrin Method” (i) Phase transfer
8. Protection of metal clusters by ligands II. Protection by thiolate ligands (B) Ligand exchange of phosphine-stabilized
9. Fractionation of gold clusters Atomic monodispersity is difficult to achieve ↓ Fractionation (A) Polyacrylamide gel electrophoresis
10. Fractionation by PAGE – suitable for hydrophilic, charged clusters Clusters with larger cores subject to stronger
11. Fractionation by PAGE Au:SG, Au:S(h-G) GSH: glutathione h-GSH: homo-glutathione Negishi, Y. et al. J. Am. Chem.
12. Fractionation by PAGE Negishi, Y. et al. J. Am. Chem. Soc. 2005, 127, 5261. High-resolution ESI
13. (B) Fractionation by GPC – suitable for hydrophobic clusters Size exclusion chromatography: Clusters with larger hydrodynamic
14. (B) Fractionation by GPC Tsunoyama, H. et al. J. Am. Chem. Soc. 2006, 128, 6036. Aun:SC18
15. (C) Size-selective etching Shichibu, Y. et al. Small 2007, 3, 835. “Size focusing” ― Thermodynamically stable
16. Stability of Au25(SG)18 Negishi, Y. et al. J. Am. Chem. Soc. 2007, 129, 11322. “Magic-numbered cluster”
17. The latest results Bond stiffness of Aun(SR)m clusters Yamazoe, S. et al. Nat. Commun. 2016, 7,
18. The latest results Bond stiffness of Aun(SR)m clusters Bond Stiffness: Au-Au(S) > bulk Au-Au > Au-Au(L)
19. The latest results Bond stiffness of Aun(SR)m clusters Yamazoe, S. et al. Nat. Commun. 2016, 7,
20. Conclusion Bottom-up preparation of gold clusters can be achieved by protection with ligands. Monodisperse clusters are
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Слайд 2

The strategy for preparing metal clusters
Bottom-up preparation
Metal ions – electrostatic repulsion

↓ reduction
Neutral metal atoms
　　↓ aggregation
Metal clusters
Problems:
Continuous aggregation 　　
Difficulty in size control 　　

Слайд 3

“Magic numbers” for bare gold clusters
Katakuse, I. et al. Int. J.

Mass Spec. Ion Proc. 1985, 67, 229.

n = 9 (8e-)

n = 21 (20e-)

n = 35 (34e-)

n = 58 (57e-)

“Superatom”
– Stability is explained by electronic shell structure.

Au: [Xe] 4f14 5d10 6s1

Слайд 4

Protection of metal clusters by ligands
I. Protection by phosphine ligands
Dative

ligands　　

Au11(PPh3)7(SCN)3
(8e-, magic number)

McPartlin, M. et al.
Chem. Commun. 1969, 1, 334.

Electronic structure of clusters
is preserved

[(PPh3)14Au39Cl6]Cl2
(31e-, hcp)

Teo, B. K. et al.
J. Am. Chem. Soc. 1992, 114, 2743.

Слайд 5

Protection of metal clusters by ligands
I. Protection by phosphine ligands
Chiral

clusters with BINAP　　

[Au11(BINAP)4Br2]+
(8e-, magic number)

Yanagimoto, Y. et al. J. Phys. Chem. B 2006, 110, 11611.

Слайд 6

Protection of metal clusters by ligands
II. Protection by thiolate ligands
– high

affinity between Au and S
“Brust-Schiffrin Method”
(B) Ligand exchange of phosphine-protected clusters
Thiolation of polymer-stabilized clusters

Слайд 7

Protection of metal clusters by ligands
II. Protection by thiolate ligands
“Brust-Schiffrin Method”

(i) Phase transfer of a gold salt (reaction is not balanced)
HAuCl4 (aq) + TOABr (tol) → [AuCl4-xBrx]TOA (tol) + HCl (aq)
(ii) Reduction of Au (III) to Au(I)
[AuCl4-xBrx]TOA + 3HSR → Au:SR + RSSR
(ii) Reduction of Au (I) to Au(0) → Aggregation
Au:SR + NaBH4 (aq, excess) → Aun(SR)m
Competition between thiolate protection and aggregation
⇒ Kinetic control of size distribution

Слайд 8

Protection of metal clusters by ligands
II. Protection by thiolate ligands
(B) Ligand

exchange of phosphine-stabilized clusters
e.g. [Au11(PPh3)8X2]+, [Au11(BINAP)4X2]+
Thiolation of polymer-stabilized clusters
e.g. Au:PVP
Dependent on the stability of parent clusters
⇒ Thermodynamic control of size distribution

Слайд 9

Fractionation of gold clusters
Atomic monodispersity is difficult to achieve
↓
Fractionation
(A) Polyacrylamide

gel electrophoresis (PAGE)
(B) Gel permeation chromatography (GPC)
(C) Size-selective etching

Слайд 10

Fractionation by PAGE
– suitable for hydrophilic, charged clusters
Clusters with larger

cores subject to stronger resistance.

Fractionation of gold clusters

Слайд 11

Fractionation by PAGE
Au:SG, Au:S(h-G)
GSH: glutathione
h-GSH: homo-glutathione
Negishi,

Y. et al. J. Am. Chem. Soc. 2005, 127, 5261.

Au:S(h-G)

Au:SG

Hydrophilic

Fractionation of gold clusters

Слайд 12

Fractionation by PAGE
Negishi, Y. et al. J. Am. Chem. Soc. 2005,

127, 5261.

High-resolution ESI MS of the fractions enabled correct determination of the compositions.

Aun(SG)m
n-m

Fractionation of gold clusters

10437 Da

10415 Da

Слайд 13

(B) Fractionation by GPC
– suitable for hydrophobic clusters
Size exclusion chromatography:
Clusters

with larger hydrodynamic diameter are excluded by pores of the gel.

Fractionation of gold clusters

Слайд 14

(B) Fractionation by GPC
Tsunoyama, H. et al. J. Am. Chem. Soc.

2006, 128, 6036.

Aun:SC18

n = 53 ± 10

n = 35 ± 6

⇒ n = 55

⇒ n = 38

Size separation with high reproducibility and resolution by recycling GPC

Fractionation of gold clusters

Слайд 15

(C) Size-selective etching
Shichibu, Y. et al. Small 2007, 3, 835.
“Size focusing”
―

Thermodynamically stable cluster Au25(SG)18 is preferentially produced from larger precursors.

Aun(SG)m

n < 25

n ≥ 25

⇒ oxidized to AuI:SG

⇒ etched into Au25(SG)18

Fractionation of gold clusters

Слайд 16

Stability of Au25(SG)18
Negishi, Y. et al. J. Am. Chem. Soc. 2007,

129, 11322.

“Magic-numbered cluster”
― Anionic form [Au25(SG)18]- is stabilized by TOA+
8 valence electrons ⇒ closed shell structure

Au(I)-SG polymers are reduced to [Au25(SG)18]- in the Brust-Schiffrin Method.

Fractionation of gold clusters

Слайд 17

The latest results
Bond stiffness of Aun(SR)m clusters
Yamazoe, S. et al.

Nat. Commun. 2016, 7, 10414.

Au-Au bonds were divided into 3 groups.
The contribution from the longest group was negligible.
⇒ FT-EXAFS data were analyzed with Au-S, Au-Au(S) and Au-Au(L).

Слайд 18

The latest results
Bond stiffness of Aun(SR)m clusters
Bond Stiffness:
Au-Au(S) > bulk

Au-Au > Au-Au(L)
Bond length:
Au-Au(S) < bulk Au-Au < Au-Au(L)
⇒ stiffness is related to length

Yamazoe, S. et al. Nat. Commun. 2016, 7, 10414.

Слайд 19

The latest results
Bond stiffness of Aun(SR)m clusters
Yamazoe, S. et al.

Nat. Commun. 2016, 7, 10414.

Au-S and surface Au-Au(S) bonds constitute rigid ring structure
⇒ Contribution to the stability

Слайд 20

Conclusion
Bottom-up preparation of gold clusters can be achieved by protection with

ligands.
Monodisperse clusters are obtained by the fractionation (PAGE, GPC, and size-selective etching).
Magic-numbered clusters are thermodynamically stable and forms dominantly. The stability is explained by their electronic or geometric structures.

The way to prepare gold clusters - Every atom makes a difference

Содержание

The strategy for preparing metal clustersBottom-up preparationMetal ions – electrostatic repulsion

“Magic numbers” for bare gold clustersKatakuse, I. et al. Int. J.

Protection of metal clusters by ligandsI. Protection by phosphine ligands Dative

Protection of metal clusters by ligandsI. Protection by phosphine ligands Chiral

Protection of metal clusters by ligandsII. Protection by thiolate ligands– high

Protection of metal clusters by ligandsII. Protection by thiolate ligands“Brust-Schiffrin Method”

Protection of metal clusters by ligandsII. Protection by thiolate ligands(B) Ligand

Fractionation of gold clusters Atomic monodispersity is difficult to achieve↓Fractionation(A) Polyacrylamide

Fractionation by PAGE– suitable for hydrophilic, charged clusters Clusters with larger

Fractionation by PAGE Au:SG, Au:S(h-G) GSH: glutathione h-GSH: homo-glutathione Negishi,

Fractionation by PAGENegishi, Y. et al. J. Am. Chem. Soc. 2005,

(B) Fractionation by GPC– suitable for hydrophobic clusters Size exclusion chromatography:Clusters

(B) Fractionation by GPCTsunoyama, H. et al. J. Am. Chem. Soc.

(C) Size-selective etchingShichibu, Y. et al. Small 2007, 3, 835.“Size focusing”―

Stability of Au25(SG)18Negishi, Y. et al. J. Am. Chem. Soc. 2007,

The latest resultsBond stiffness of Aun(SR)m clusters Yamazoe, S. et al.

The latest resultsBond stiffness of Aun(SR)m clusters Bond Stiffness:Au-Au(S) > bulk

The latest resultsBond stiffness of Aun(SR)m clusters Yamazoe, S. et al.

ConclusionBottom-up preparation of gold clusters can be achieved by protection with

Похожие презентации

The strategy for preparing metal clusters
Bottom-up preparation
Metal ions – electrostatic repulsion

“Magic numbers” for bare gold clusters
Katakuse, I. et al. Int. J.

Protection of metal clusters by ligands
I. Protection by phosphine ligands
Dative

Protection of metal clusters by ligands
I. Protection by phosphine ligands
Chiral

Protection of metal clusters by ligands
II. Protection by thiolate ligands
– high

Protection of metal clusters by ligands
II. Protection by thiolate ligands
“Brust-Schiffrin Method”

Protection of metal clusters by ligands
II. Protection by thiolate ligands
(B) Ligand

Fractionation of gold clusters
Atomic monodispersity is difficult to achieve
↓
Fractionation
(A) Polyacrylamide

Fractionation by PAGE
– suitable for hydrophilic, charged clusters
Clusters with larger

Fractionation by PAGE
Au:SG, Au:S(h-G)
GSH: glutathione
h-GSH: homo-glutathione
Negishi,

Fractionation by PAGE
Negishi, Y. et al. J. Am. Chem. Soc. 2005,

(B) Fractionation by GPC
– suitable for hydrophobic clusters
Size exclusion chromatography:
Clusters

(B) Fractionation by GPC
Tsunoyama, H. et al. J. Am. Chem. Soc.

(C) Size-selective etching
Shichibu, Y. et al. Small 2007, 3, 835.
“Size focusing”
―

Stability of Au25(SG)18
Negishi, Y. et al. J. Am. Chem. Soc. 2007,

The latest results
Bond stiffness of Aun(SR)m clusters
Yamazoe, S. et al.

The latest results
Bond stiffness of Aun(SR)m clusters
Bond Stiffness:
Au-Au(S) > bulk

The latest results
Bond stiffness of Aun(SR)m clusters
Yamazoe, S. et al.

Conclusion
Bottom-up preparation of gold clusters can be achieved by protection with