Studies using Ag51BDT19 and Ag29

Electronic Supplementary Information (ESI) for the paper:

Unusual reactivity of dithiol protected clusters in comparison to monothiol protected clusters: Studies using Ag

₅₁

BDT

₁₉

and Ag

₂₉

BDT

₁₂

Atanu Ghosh, Debasmita Ghosh, Esma Khatun, Papri Chakraborty and Thalappil Pradeep*

Department of Chemistry, DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE)

Indian Institute of Technology Madras Chennai, 600 036, India

E-mail: pradeep@iitm.ac.in Table of content:

Name Description

Page no.

S1 Characterization of Au₂₅BT₁₈ and Au₂₅OT₁₈ clusters 2

S2 UV-vis and ESI MS spectrum of cluster II 3

S3 Expanded ESI MS region of cluster I 4

S4 MALDI MS data of clusters I and II 5

S5 Laser fluence dependent MALDI MS data of cluster I 6

S6 SEM/EDAX 7

S7 XPS 8

S8 ESI MS spectrum of cluster I 9

S9 Comparison of luminescence property of cluster I and cluster II 10 S10 Time dependent UV-vis spectra of the reaction between cluster I and

Au₂₅BT₁₈

11 S11 Concentration dependent ESI MS spectra of the reaction between

cluster I and Au25BT18

12 S12 Reactions of cluster I with BT and OT ligated Au₂₅ clusters 13 S13 Comparison of reactivity of cluster I and cluster II with Au₂₅BT₁₈ 14

S14 Reaction of cluster II with Au25BT18 15

S15 Reaction of Au₂₅BT₁₈ cluster with BDT thiol 16 S16 Time dependent ESI MS spectra for inter-cluster conversion process 17 S17 A UV-vis study of the inter-cluster conversion process 18

S18 Transformation of Cluster I to cluster II 19

400 600 800 1000 0.0

0.3 0.6 0.9

Absorbance

Wavelength (nm)

4000 6000 8000

m/z

400 600 800 1000

0.0 0.3 0.6 0.9

Wavelength (nm)

Absorbance

6000 8000 10000

m/z

A) B)

Characterization of Au25BT18 and Au25OT18 clusters

Fig. S1 A) UV-vis spectrum of as synthesized Au25BT18 cluster which matches with the published report.¹ Inset: ESI MS spectrum of the cluster solution. Presence of single peak at m/z 6530 confirms the composition and purity of the sample. B) UV-vis spectrum of Au25OT18

cluster. Inset: ESI MS spectrum of the cluster solution. Composition and purity of the cluster is confirmed from the presence of single peak at m/z 7540.¹

400 600 800 1000 0.0

0.2 0.4 0.6 0.8

Absorbance

Wavelength (nm)

1200 1600 2000

m/z

1599 1602 1605 1608

m/z

A) B)

6 mg 11 mg 16 mg

[Ag₂₉BDT₁₂]^3-

UV-vis and ESI MS spectrum of cluster II

Fig. S2 A) UV-vis spectra of DMF solutions of the clusters. Black, red and blue traces are for the

solutions of 1A3, B3 and C3 of main manuscript, respectively. All the spectra match with those of [Ag29BDT12]^3- (cluster II).² Inset: ESI MS of the cluster solution. As all the solutions gave the same spectra , we have presented only one of them. Presence of a single peak at m/z 1603 confirms the formation of cluster II.² B) Comparison of experimental (black trace) and simulated isotopic pattern (red trace) which matches perfectly.

2716 2720 2724 2728

m/z

2721.0 2721.5 2722.0

m/z 0.33

Expanded ESI MS region of cluster I

Fig. S3 Peak at m/z 2721.56 is expanded here. Separation between the two peaks is m/z 0.33 which confirms that the cluster has 3- charge.

3000 6000 9000 12000 15000

m/z

4005 4050 4095 4140 4185

m/z _{8100 8190 8280 8370 8460}

m/z

[Ag51BDT19]1- [Ag52BDT19]1- [Ag53BDT19]1-

[Ag51BDT19]2- [Ag52BDT19]2- [Ag53BDT19]2-

4770 4860 4950 5040 5130

m/z [Ag29BDT12]1- [Ag30BDT12]1- [Ag31BDT12]1-

MALDI MS data of cluster I and cluster II

Fig. S4 MALDI MS spectra of cluster I (black trace) and cluster II (red trace). The spectra were

measured in the -ve mode at threshold laser fluence. Monoanioninc and dianionic peaks of the cluster I are expanded which shows the presence of silver attached peaks along with the molecular ion ([Ag51BDT19]^-) peak. MALDI MS spectrum of the purified cluster II (red trace) also shows the presence of silver attached peaks along with the molecular ion ([Ag29BDT12]^-) peak. This silver attached peaks with the molecular ion peak may be a characteristic feature of dithiol protected clusters.

27000 36000 45000

9000 18000 27000 36000 45000

m/z

18000 27000 36000 45000

15600 16200 16800 17400

m/z

dimer

trimer

tetramer

pentamer

Expanded dimer region

Laser fluence dependent MALDI MS data of cluster I

Fig. S5 MALDI MS data of cluster I measured at higher laser fluence. Expansion of higher mass

region shows the presence of peaks at regular intervals of ~m/z 8100 along with the molecular ion peak. These higher mass peaks are due to the formation of dimer (~m/z 16200), trimer (~m/z 24300), tetramer (~m/z 32400) and pentamer (~m/z 40,500) of Ag51BDT19 cluster which are marked. Inset: The peak corresponding to the dimer is expanded which also shows the silver attached peaks.

(keV)

A) B) C)

D) E)

SEM image AgL

S K P K

SEM/EDAX

Fig. S6 (A) EDAX spectrum of Ag51BDT19 and (B) SEM image of Ag51BDT19 aggregate from which the EDAX spectrum was taken. Ag:S atomic ratio measured is 1:0.76, as expected (actual is 1:0.74).

366 372 378 160 162 164 166

Binding energy (eV)

In te n si ty

d

_5/2

d

_3/2

Ag 3d

p

_3/2

p

_1/2

A) B) S 2p

XPS

Fig. S7 (A) and (B) represent the XPS spectra for Ag 3d and S 2p, respectively with multiple component fitting. It shows that Ag is almost in the zero oxidation state.

2700 3000 3300

m/z

[Ag₅₁(BDT)₁₉(TPP)_X]^3-

X= 3 X= 2 X= 1 X= 0

ESI MS spectrum of cluster I

Fig S8 ESI MS spectrum of the purified cluster in the negative mode. The peaks are separated by m/z = 87.5. As the cluster has 3- charge, the peak separation of 87.5 is assigned to the loss of one phosphine (molecular mass 262.3) from the parent ion. It shows the sequential dissociation of three phosphines from the parent peak. The peak at m/z 2721.56 (where X= 0) is corresponds to [Ag51(BDT) 19]^3-. Therefore the assigned composition of the parent material is [Ag51(BDT)

19(TPP)3]^3-.

500 600 700 800

In te ns ity

Wavelength (nm)

Cluster II Cluster I

Photograph under UV light Cluster I

Cluster II

λ_ex= 450

Comparison of luminescence property of cluster I and cluster II

Fig S9 Comparison of luminescence property of Ag51 (cluster I) and Ag29 (cluster II) clusters.

Both, the luminescent spectra and the photograph under UV light (inset) show that the cluster I is weekly luminescent in comparison to cluster II.

400 600 800 1000 0.0

0.4 0.8 1.2

A bs or ba nc e

Wavelength (nm)

Parent cluster I

Cluster I + Au₂₅BT₁₈after 15 min

Cluster I + Au₂₅BT₁₈after 45 min

Time dependent UV-vis spectra of the reaction between cluster I and Au25BT18

Fig. S10 Time dependent UV-vis spectra of inter-cluster reaction.

[Ag_51-xAu_xBDT₁₉]^3-

2700 2730 2760 2790 2820

m/z

3 = x 1 2

0

Parent cluster I 10 µL 20 µL 40 µL 80 µL

Concentration dependent ESI MS spectra of the reaction between cluster I and Au25BT18

Fig. S11 Reaction of cluster I (fixed concentration) with increasing concentrations of Au25BT18

clusters. As the amount of Au25BT18 cluster increases in the reaction medium, more and more silver of cluster I get substituted by gold of Au25BT18 cluster leading to the formation of [Ag51- xAu_xBDT₁₉]^3-alloy.

m/z m/z

(BDT, m/z 142)

(BT, m/z 90)

(OT, m/z 146)

4 = x 2 3

Ag51-xAuxBDT19

2 = x 1

0

Ag51-xAuxBDT19

with Au₂₅OT₁₈ with Au25BT18

with Au₂₅OT₁₈ with Au25BT18

= x 1 0

2

Au_25-yAg_yOT₂₅

A) B) 3

C) D)

2790 2820 2850

2730 2760 2790

7290 7380 7470 7560

m/z

Reactions of cluster I with BT and OT ligated Au25 clusters

Fig. S12 A) Compositions and masses of protecting ligands, BDT, OT and BT thiols. B) The Au25OT18 region during reaction with cluster I. The peaks are due to the formation of [Au25- yAgyBT18]^- alloy cluster. No peaks other than those of metal exchange were found. C) and D) compares the [Ag51-XAuXBDT19]^3- region while cluster I reacting with BT and OT ligated Au25

clusters. No new peaks were observed here. Absence of new peaks upon using the differently ligated Au25 clusters confirms that the ligand shell is not involving for this type of reaction.

Au25

Ag51

Ag29

Ag₂₉+ Ag₅₁+ Au₂₅ Ag_51-xAu_x + Ag₂₉

30 min

1500 3000 4500 6000

m/z

Comparison of reactivity of cluster I and cluster II with Au25BT18

Fig. S13 Reactions of equimolar mixture of cluster I and II with Au25BT18 cluster. After 30 min of reaction cluster I disappeared (highlighted portion) whereas cluster II underwent slow reaction.

1600 1650 1700

m/z

6150 6300 6450 6600

m/z

[Ag₂₉BDT₁₂]^3-

[Ag₂₈Au₁BDT₁₂]^3-

[Ag₂₇Au₂BDT₁₂]^3-

[Au₂₅BT₁₈]^-

[Au₂₄Ag₁BT₁₈]^- [Au₂₃Ag₂BT₁₈]^-

[Au₂₂Ag₃BT₁₈]^- A)

B)

Reaction of cluster II with Au25BT18

Fig. S14 ESI MS spectra of reaction of cluster II with Au25BT18 cluster. A) Cluster II undergoes only metal exchange reaction leading to the formation of [Ag29-xAuxBDT12]^3- alloy cluster. B) On the other side, Au25BT18 also under goes metal exchange reaction leading to the formation of [Au25-xAgxBT18]^- alloy cluster.

6500 6600 6700 6800 6900

m/z

Au₂₅BT_18-xBDT_x

x = 0 1 2 3 4 5

Parent Au₂₅BT₁₈ 15 min

30 min 60 min

Reacion of Au25BT18 cluster with BDT thiol

Fig. S15 Time dependent ESI MS spectra for the reaction of Au25BT18 with BDT thiol. As time increases more and more BT ligands of Au25BT18 get exchanged by BDT thiol.

1600 2000 2400 2800

m/z

[Ag₅₁BDT₁₉]^3- [Ag₅₀BDT₁₉]^3-

[Ag₂₉BDT₁₂]^3- [Ag29BDT12]^2-

2400 2405 2410

m/z

1600 1604 1608

m/z

[Ag29BDT12]^2- [Ag29BDT12]^3-

3 h 6 h 12 h 18 h

A) B)

C)

Time dependent ESI MS spectra for inter-cluster conversion process

Fig. S16 A) Time dependent ESI MS spectra for the reaction of cluster I with DMBT (15 µL).

As time progresses, peak at m/z 2721 = due to the parent cluster I disappears slowly. At the same time, peak at m/z 1603 which is due to the cluster II increases gradually. After 18 h of reaction, cluster I was completely converted to cluster II. Upon addition of DMBT, cluster I immediately loses one Ag ion and forms [Ag50BDT19]^3- which is marked in the figure. B) and C) Compare the experimental (black trace) and simulated (res trace) isotopic distribution for 2- and 3- charge states of cluster II.

400 600 800 1000 0.0

0.3 0.6 0.9

A bs or ba nc e

Wavelength (nm)

Parent cluster I

Cluster formed from cluster I Parent cluster II

A UV-vis study of the inter-cluster conversion process

Fig. S17 Optical absorbance spectra where spectra of cluster I (black trace) and II (blue trace) are compared with the reaction product (red trace). It confirms the formation of cluster I.

400 600 800 0.0

0.4 0.8 1.2

Wavelength (nm)

Absorbance ^{Cluster I}

After 2 h After 4 h Cluster I + 1-Butanethiol (10µL)

400 600 800

0.0 0.4 0.8 1.2

Absorbance

Wavelength (nm)

Cluster I after1 h after 2h

Cluster I + 2,5-Dichlorobenzenethiol (10µL)

A) B)

Transformation of Cluster I to cluster II

Fig. S18 A) Time dependent UV-vis spectra for the transformation of Ag51 to Ag29 in presence of 1-butanethiol. B) Time dependent UV-vis spectra for the transformation of Ag₅₁ to Ag₂₉ in presence of 2,5-dichlorobenzenethiol.

2 L. G. AbdulHalim, M. S. Bootharaju, Q. Tang, S. Del Gobbo, R. G. AbdulHalim, M. Eddaoudi, D.-e. Jiang and O. M. Bakr, J. Am. Chem. Soc., 2015, 137, 11970-11975.