Supporting information (SI) for the · PDF fileSupporting information (SI) for the paper: ......

1

Supporting information (SI) for the paper:

Supramolecular Functionalization and Concomitant Enhancement in

Properties of Au25 Clusters

Ammu Mathew, Ganapati Natarajan, Lauri LehtovaaraϮ, Hannu HäkkinenϮ, Ravva Mahesh

Kumar‡, Venkatesan Subramanian ‡, Abdul Jaleel# and Thalappil Pradeep*

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

Technology Madras, Chennai 600036, India.

% Departments of Chemistry and Physics, Nanoscience Center, University of Jyväskylä, Finland.

‡Chemical Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai 600020, India.

#Proteomics Core Facility, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram 695014, India

*E-mail: [email protected]

Table of contents

Number Description Page

no.

S1 Absorption spectra for various Au:BBSH ratios in cluster synthesis. 3

S2 MALDI (L) MS of Au25SBB18 QC in positive and negative ion modes 4

S3 MALDI (L) MS of Au25SBB18 QC at different laser intensities 5

S4 ESI MS of Au25SBB18 in negative ion mode (low mass region) 6

S5 TEM images of Au25SBB18 7

S6 SEM and EDAX characterization of Au25SBB18 QC 7

S7 SEM images of β-CD after reaction in water and THF:water (30:1)

solvent medium 8

S8 LDI MS of the aqueous layer during synthesis of CD functionalized

Au25SBB18 9

2

S9 MALDI (L) and MALDI (R) MS of Au25SBB18 with increasing

SBB:CD ratios in solution 10

S10 MALDI TOF TOF MS of Au25SBB18 wth other ratios of SBB:CD in

solution 11

S11 Dependence of laser fluence on the MALDI (L) and MALDI TOF TOF

mass spectra of Au25SBB18∩CD4 12

S12 NIR luminescence of Au25SBB18 QC 13

S13 DFT calculations and structural modeling of Au25SBB18,

Au25SBB18∩CD4 and BBSH∩CD adducts 14-17

S14 1H NMR of CD, Au25SBB18 and Au25SBB18∩CD QCs 17

S15 2D COSY spectrum of Au25SBB18∩CD QC 18

S16 LDI MS of BBSH∩CD inclusion complex in the positive ion mode 18

S17 ESI MS and tandem mass spectrometry BBSH∩CD inclusion complex 19-20

S18 Binding constant of BBSH∩CD inclusion complex 21

S19 1H NMR and 2D COSY spectrum of BBSH∩CD inclusion complex 22

S20 UV data of ligand exchange of PET with SBB∩CD ligands on

Au25PET18 QCs 23

S21 Effect of metal ion (Cu2+) on the luminescence of Au25SBB18 and

Au25SBB18∩CD QCs 24

S22 Effect of excess ligand (BBSH) on bare and BBSH∩CD incorporated

Au25PET18 QCs 25

S23 Effect of AdT: A case of a competitive guest 26

3

450 600 750 900

0.1

0.2

0.3

Ab

sorb

ance

Wavelength (nm)

1: 9

1: 18

1: 60

1: 90

600 700 800 900

Wavelength (nm)

1: 9

1: 18

1: 60

1: 90

1: 9

1: 18

1: 60

1: 90

B

A

400 600 8000.0

0.2

0.4

0.6

Ab

sorb

ance

Wavelength (nm)

1: 2

1: 3

1: 4.5

600 800 1000

1: 2

1: 3

1: 4.5

Supporting information 1

Figure S1. Effect of UV-vis optical absorption spectra for various Au:BBSH ratios used for

cluster synthesis. An optimum Au:S ratio of 1:6 was employed for typical synthesis of

Au25SBB18 (see Figure 1 in paper). While lower thiol ratios (A) showed significant changes

in the absorption profile indicating that clusters of higher core sizes are getting formed, even

a ten fold increase in thiol (B) compared to the optimised synthesis did not seem to yield still

smaller clusters.

4

20000 40000 60000 80000

Inte

nsi

ty

m/z

positive mode

negative mode

negative

n = 2 1 0

positive

4000 8000 12000

m/z

n = 3 2 1

Au21(SBB)14-2n(S)2n

Au25(SBB)18-2n(S)2nAu25SBB18


Figure S2. Full range MALDI (L) mass spectra of Au25SBB18 cluster in both positive and

negative ion modes. Fragmentation due to the C-S cleavage of SBB ligand on the cluster

surface can be observed apart from the molecular ion peak (these features are expanded in the

inset). Loss of [Au4L4] fragment from the parent cluster is a typical phenomenon in Au25

clusters. Here, we observed similar fragments corresponding to [Au4SBB4BB2n] loss, where n

= 1, 2, 3 in the negative ion mode from parent Au25SBB18. The additional BB losses observed

in the negative mode (red trace in inset) could be due to the facile C-S cleavage as in the case

of the molecular ion peak at 8151 Da. DCTB was used as the matrix and threshold laser

intensities were employed for all the measurements.

5

1284

1323

1432

1482

1551

Laser

intensity

1373

10000 20000 30000

m/z


Figure S3. MALDI (L) mass spectra of the purified Au25SBB18 cluster at different laser

intensities in the positive mode. Control over the laser intensity is vital to observe the

molecular ion peak of the cluster without fragmentation. Laser intensity (shown at the right

extreme) is as given by the instrument and has not been calibrated to a standard unit.

6

1000 2000 3000 40000

4000

Inte

nsi

ty

m/z

(AunSBBn+1)-

n = 1 2 3 4

(Au1SBB2)-

(Au2SBB3)-

(Au3SBB4)-

(Au4SBB5)-

(Au3SBB3S1)-

Negative mode


Figure S4. ESI MS of Au25SBB18 in negative ion mode showing fragments from the cluster

in the low mass region.

7

A B

20 nm 10 nm

Au: S

1 : 0.73

S KAu M

Au L O K C K

30 µm


Figure S5. TEM images of Au25SBB18. Two magnifications are shown. Unlike in typical

thiolated clusters, these samples are resistant to electron beam induced aggregation.


Figure S6. SEM and EDAX characterization of Au25SBB18 cluster. Carbon and aluminium are from the substrate used for the measurement. Contrast of carbon is low due to the use of carbon tape as the substrate. The scale is same for all images.

8

A B C


Figure S7. SEM images of (A) native β-CD powder, (B) drop cast β-CD solution in water and (C) drop cast β-CD solution in THF:water (30:1) mixture, after sonication. The formation of needle-like superstructures by self assembly occurred only in the case of reaction in THF:water (30:1) solvent mixture. Presence of minimal amount of water molecules can enhance the possibility of intermolecular hydrogen bonding between the hydroxyl group present on the outer rim of CD molecules. Control experiments in water (B), did not result in formation of superstructures. Thus the dispersion of β-CD molecules by sonication in THF and their subsequent self assembly by re-formation of the strong hydrogen bonding between the CDs with the aid of THF results in these superstructures.

9

300

350

400In

ten

sity

m/z

400

350

300

24000 48000 72000

1400010000 18000

m/z


Figure S8. LDI mass spectrum of the aqueous layer, post synthesis of the CD-functionalised Au25SBB18 clusters. Addition of excess water to the microtubular arrangement of CD and cluster leads to the formation of Au25SBB18∩CDn (where n=1-4). Though we found better mass spectral intensities for the adducts from the organic layer (see Figure 2 in main text), probably due to the existence of more number of hydrophobic SBB groups on the cluster surface (18-n, where n<4), analysis of the aqueous layer showed a broad peak at higher mass range too albeit with reduced intensity. Inset shows an expanded view. Peak maximum corresponding to Au25SBB18∩CD4 is marked with a line.

10

30000 60000 90000

m/zm/z

12.6 kDa

10.4 kDa

11.5 kDa

(Au25SBB18∩CD4)

(Au25SBB18∩CD3)

(Au25SBB18∩CD2)

9.2 kDa(Au25SBB18∩CD1)

30000 60000 90000

Au25SBB18

1: 1.2

1: 1

1: 0.8

1: 0.05

1: 0.03

20000 30000 40000

m/z

Linear mode Reflectron mode

1 2 3 4

10000 20000 30000 4000010000


Figure S9. Positive mode MALDI (L) and MALDI (R) mass spectra of Au25SBB18 with

increasing SBB:CD ratios in solution. The peak maxima shift with increasing BBS:CD ratio.

This gradual increase is marked. Peak corresponding to parent Au25SBB18 is marked using a

*. These peak positions are the same in both the data sets, but in the reflectron mode the

peaks are better resolved as the resolution is improved. These peaks resolve even better in the

MALDI TOF TOF mode (see S10).

11

(x, y) =

1, 1

1, 2

1, 3

1, 4

0, 0

Au25SBB18-xSx∩CDy

8000 16000 24000

Inte

nsi

ty

m/z

B

D

F

H

J

L

N

P

SBB:CD ratio

in solution

1:1.2

1:1

1:0.95

1:0.8

1:0.5

1:0.05

Au25SBB18

1:1.1


Figure S10. MALDI TOF TOF mass spectra of Au25SBB18 with increasing SBB:CD ratios

(green to brown) in solution. The peaks are better resolved than in S9.

12

15000 30000 45000

Inte

nsi

ty

m/z

B

G

D

E

F

A B

10000 15000 20000 25000

Inte

nsi

ty

m/z

Laser

fluence

Laser

fluence


Figure S11. MALDI (L) mass spectra (A) and MALDI TOF TOF mass spectra (B) of Au25SBB18∩CD4 at different laser intensities in the positive mode. Note that though the background of the spectra increases with more laser fluence, the peak maxima and relative individual peak intensities remain the same except for red trace in (B) wherein peak due to Au25SBB13S5 (marked with a *) gain intensity at higher laser fluence due to cleavage of C-S bond and loss of CDs. There are threshold laser powers above which fragmentations occur.

13

900 1000 1100 1200 13000.0

900.0k

Inte

nsi

ty

Wavelength (nm)

800 1000 1200 14000.0

800.0k

Inte

nsi

ty

Wavelength (nm)

λex

825

882

894

905

916

938

950

971

979

992

Au25SBB18

BBSH in THF

BBSH in THF + NaBH4

Au(I)SBB in THF

(A)

(B)


Figure S12. NIR luminescence observed from the bare Au25SBB18 cluster at (A) various

excitation wavelengths and (B) comparison with the spectra (λex 992 nm) of various starting

materials.

14

Supporting Information 13

Structural optimization of Au25SBB18

The cluster was rotated so that the x-axis lay along the axis of the cluster passing through its center and the bridging sulfur atoms which were spaced the furthest distance apart. Cluster boundary conditions were used and the size of the simulation box was chosen to be 34 Å, leaving about 9 Å of buffer space around the molecule. A negative charge was added to the molecule.

Au25SBB18∩CD4

Ligand structure of Au25SBB18 and CD attachment

The precise arrangement around any given ligand will affect whether that ligand may be a likely one for CD complexation. It was observed that bridging ligands were generally surrounded by ligands which were quite close to it, while the ligands neighboring a non-bridging ligand were spread further apart. The number of nearest-neighbor ligands to a CD centered on a chosen ligand was four.

The model of Au25SBB18∩CD4 was constructed by making attachments of CDs to the DFT optimized structure of Au25SBB18 using molecular builder software. The narrow side of the CD was attached first as this would reduce steric hindrance and this configuration had a lower binding energy as an isolated complex. The choice of ligands also affects the depth of penetration of the CD onto the ligand, which is lesser in the case of the bridging ligands due to greater steric hindrance from the neighbouring ligands. For non-bridging ligands both the aromatic BBS protons and t-butyl group protons would be close to the inner CD protons, which also agrees with the NMR data. For bridging ligands the inner H3 and H5 protons of the CD would be closer to the t-butyl groups. The non-bridging ligand denoted by (y,-z), in the notation described in the main paper, was easily accessible due to the widely separated positions of the surrounding ligands and hence was chosen for making the first attachment of the CD. The attachment was made in a stepwise fashion starting by including the t-butyl group and then by bringing the narrow end of the CD further over the ligand and then reoptimizing using a UFF force field until its position was in agreement with the NMR data. We also rejected position changes which increased the total energy. During the optimization, the core and staple atoms, i.e. the Au and S atoms, were kept fixed in their positions from DFT, while the other atoms were allowed to move. This process was repeated three more times by making CD attachments to the (-z, -x), (x,-y) and (z,-x) non-bridging ligands which were easily accessible. The energy of the final structure in the UFF force field was 60,323 kcal/mol. From our calculations on BBSH∩CD, it is energetically favourable for the included ligand to be at an angle with respect to the CD. Tilting the CD to the angles found in the optimized geometries of BBSH∩CD was found difficult due to the presence of the neighboring ligands. The relative angle of the CD and included ligand varies due to the differing orientations of the included ligand and its neighbors. We remark here that further force-field calculations and molecular dynamics simulations would be necessary to determine more precise attachment

15

A B

C

z

y

x

y

z

x

z

x

y

geometries as several different configurations which differ in depth and angle of attachment are consistent with the NMR data.

Figure S13. Different views of the Au25SBB18∩CD4 model. Hydrogen atoms are not shown

on the SBB ligands for clarity. Sulfur and gold atoms are shown in green and gold,

respectively, while the carbon atoms of the bridging and non-bridging ligands are shown in

blue and magenta, respectively. The four attached CDs are shown in cyan in the stick

molecular representation. The cartesian x, y, and z axes are shown by the red, green and blue

arrows, respectively.

DFT calculations on BBSH∩CD

In this section we give full details of the DFT calculations performed on the BBSH∩CD inclusion complexes and discuss some of the theoretical results presented in the paper in

16

more detail. All calculations were performed with the Gaussian 09 code.1 The experimental structure of β-cyclodextrin (C70H42O35) was obtained from the Hic-Up Database and was based on the Protein Data Bank file pdb1z0n.ent.2 As the downloaded structure was without hydrogen atoms these were added to this structure and the hydrogen positions were optimized at B3LYP/6-31G* keeping all the other atoms fixed in the same positions as experiment. The geometry of BBSH molecule (C11H15SH ) was obtained from the web database ChemSpider.3 A geometry optimization at the B3LYP/6-311+G** level was carried out. The optimization resulted in small changes in the geometry, as the plane of the benzene ring rotated to be perpendicular to the plane containing the C1-C2 bond (carbons are numbered starting from the sulfur end). The above geometries of CD and BBSH were then used for creating the initial configurations of two BBSH∩CD adducts. The BBSH molecule was inserted into the CD cavity with the t-butyl group going in first. The alignment of the BBSH molecule was such that its C1-C2 axis was along the axis of the CD passing through the CD centre and perpendicular to the planes of its openings. Two such initial configurations were constructed by insertion into the wide and narrow ends of the CD. The geometry optimizations were carried out using the meta-GGA hybrid functional m052-X, which describes more accurately the non-covalent interactions found in the adducts, in conjunction with 6-31G* and 6-31+G** basis sets. During the optimization, the CD atoms were kept fixed and only the BBSH atoms were allowed to move. This was done not only to speed up the computations but also because β-CD adopts what is known as the anhydrous configuration after a full DFT geometry optimization,4 which is different from its structure in a solvent. The optimized geometries of the adducts are shown in Figure 4D (narrow end entry) and 4E (wide end entry), indicating the stability of these adducts due to non-covalent interactions. We did not find a significant change in the geometries with increase in the size of the basis set, and we have presented results using 6-31G* in Figures 4D and 4E. The BBSH molecule adopted a slanted configuration with its C1-C2 axis parallel to the side of the CD in both the narrow and wide entry cases. Binding energies of the narrow and wide entry configurations were performed using the Boys counterpoise correction method5 with the m052-X/6-31+G** level of theory. The binding energy is about 2 kcal/mol less for the narrow case. We might attribute this to stronger π-bonding between the BBSH aromatic ring and the inner CD protons in the narrow case because of the shorter inter-proton distance caused by the narrowing of the profile of the CD. A careful note of the relative positions of BBSH and CD protons was made in order that agreement with NMR experimental data might be evaluated. Referring to Figure 4D and 4E we see the following. In the narrow case, the Hb

group protons are located around the level of the O-H1 protons, the lower aromatic Hc protons (closest to the sulfur end) are around the level of the H2 protons of CD, the upper aromatic Hd protons are situated around the level of the H3 CD protons, while the t-butyl group He protons are situated between the level of the H5 and H6

CD protons. In the wide case, the Hb protons are slightly below the H6 protons and not inside the CD, the lower aromatic Hc protons are at the H5 proton level, the upper aromatic Hd

protons are the at H3 proton level, while the t-butyl group He protons are between the H5, H6 and H7

protons. NMR data suggests an interaction between both the aromatic and t-butyl group protons of BBSH with the H3 and H5 inner CD protons, which is also in good general agreement with both the structures. However it is not possible to identify the specific NMR fingerprints of

17

3.03.23.43.63.84.04.24.4 ppm 0.91.01.11.21.31.41.51.61.7

Au25SBB18CD4

Au25SBB18CD2

Au25SBB18

CD

H3

H2 and H4

H6 and H5

Hb

He

3.03.23.43.63.84.04.24.4 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.9 ppm

each of the structures from the experimental data which suggests the possibility of NMR calculations at DFT level. The arrangement of the included ligand and the CD were found to be different for inclusion complexes formed with ligands attached to the cluster rather than isolated ligands. Firstly, the presence of a gold core and -Au-S-Au-S-Au- staples attached to the sulfur of the SBB ligand decreases the penetration depth of the CD. Secondly, the steric hindrance caused by the presence of about four or five ligands around the CD decreases both the CD penetration depth and the angle between the CD and the ligand.


Figure S14. 1H NMR of β-CD, Au25SBB18 and Au25SBB18∩CDx in 1:1 solvent mixture of

DMSO-d6 and CDCl3 at 25 oC. Here signals due to unreacted He protons of BBS can also be

observed (green and pink trace) which suggests the existence of free and complexed BBS on

the cluster.

18

500 1000 1500 2000 2500

0.0

2.0k

4.0k

Inte

nsi

ty

m/z

1250 1300 1350

m/z

H

Experimental

Theoretical

[CD+BBSH+H]+

1316


Figure 15. 2D COSY spectrum of Au25SBB18∩CD4 in 1:1 mixture of DMSO-d6 and CDCl3

at 25 oC.


Figure S16. LDI MS of BBSH∩CD in the positive ion mode.

19

1000 1100 1200 1300 1400

0.0

4.0x104

Inte

nsi

ty

m/z

1315.5

[CD + Na]+

1157.8

[CD+ BBSH + H]+

[CD + H]+

1135.6

β-CD

β-CD + BBSH

Theoretical

Positive mode 1315 13201315 1320

[β-CD+BBSH+H]+

[CD + BBSH + Na]+

1337.8

1135 1139

[β-CD+H]+

1137


Figure S17a. ESI MS of β-CD and BBSH∩CD inclusion complex in the positive ion mode.

Expanded views are given in the inset.

20

1100 1200 1300 1400 1500

m/z

1100 1200 1300 1400 1500

m/z

1100 1200 1300 1400 1500

1100 1200 1300 1400 1500

m/z

m/z

A

B

[BBSH∩CD]+

m/z 1316

[CD]+

m/z 1136

Loss of BBSH

[BBSH∩CD]+

m/z 1316

Loss of BBSH

[CD-Na]+

m/z 1158

[BBSH∩CD-Na]+

m/z 1338

[CD]+

m/z 1136

MS2 of 1316 peak

MS2 of 1338 peak

Collision

energy

Collision

energy

Figure S17b. Tandem mass ESI spectra (positive ion mode) for the peak at m/z 1316 (A) and

1338 (B) with increasing collision energy. Fragment ions are also marked. In the MS2

spectrum of m/z 1338, the peaks formed at m/z 1158, 1316 and 1136 correspond to the loss

of BBSH (180 Da) and Na (23 Da) from the parent ions.

21

360 450 540 630

0

1x107

2x107

B

D

F

H

J

L

Inte

nsi

ty

Wavelength (nm)

0 600 1200 1800

0.0

1.0x10-7

2.0x10-7

1/[

F-F

0]

1/[CD]0

(A) (B)


The binding constant of a simple host-guest adduct, BBSH∩CD was measured in the same

medium used for complexation of clusters using fluorescence spectral titrations.6, 7 From the

modified Benesi-Hildebrand equation, the linear plot of the reciprocal of the change in

fluorescence intensity (∆F) and the reciprocal of the molar concentration of cyclodextrin

([CD]0) indicated a 1:1 stoichiometric complex with a binding constant of ~1776 M-1.

However, for Au25SBB18 and CD, such measurements using normal complexation titration,

NMR, etc. were not attempted as multiple stoichiometries, Au25SBB18∩CDn (where n=1 to

4), can exist in solution thereby making calculation of binding constants difficult.

Figure S18. (A) Emission spectra of BBSH solution (6.9*10-5 M) in THF/water mixture in the presence and absence of β-CD. From bottom to top: [β-CD] = 0, 0.5 × 10-3, 1 × 10-3, 2 × 10-3, 3 × 10-3 and 4 × 10-3 M. (B) Plot of reciprocal of the change in fluorescence intensity (∆F) and the reciprocal of the molar concentration of cyclodextrin ([CD]0)

22

1

2

3

4

5

6

7

1.01.52.02.53.03.54.04.55.05.56.06.57.07.5 ppm

BBSH∩CD

CDHb

H3

H3’

H2, H2’, H4 and H4’

H5

4.4 4.2 4.0 3.8 3.6 3.4 3.2 3.0 ppm

ppm3.0 2.5 2.0 1.53.54.04.55.05.56.06.57.07.5


Figure 19a. Comparison of 1H NMR of CD (blue trace) and BBSH∩CD (green trace)

inclusion complex in 1:1 mixture of DMSO-d6 and CDCl3 at 25 oC.

Figure 19b. 2D COSY spectrum of BBSH∩CD in 1:1 mixture of DMSO-d6 and CDCl3 at 25 oC.

23

500 600 700 800 9000.0

Ab

sorb

ance

Wavelength (nm)

Au25pet18

B

D

F

1 : 0

1 : 0.05

1 : 0.1

1: 0.5

Au25PET18-x(SBB∩CD)x

Au25PET18

PET SBB SBB∩CD


Figure S20. Effect of UV-vis absorption spectra after ligand exchange reaction of Au25PET18

with SBB∩CD (as incoming ligand). The PET:SBB∩CD ratios are shown.

24

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

0

20

40

60

80

100

% L

um

inescen

ce In

ten

sit

y

Volume of Cu(II) added (mL)

Au25

BBS18

Au25

BBS18

+ CD

Au25SBB18

Au25SBB18∩CD4


Figure S21. Quenching of (A) bare Au25SBB18 and (B) Au25SBB18∩CD4 upon treatment with an aqueous solution of 250 mM Cu2+ solution (note that clusters were taken in THF solvent so as to allow better miscibility). The spectra were measured after 5 minutes of addition.

25

4000 8000 12000 16000

m/z

B

C

E

32

1

45

67

89

1011

1213

1415

1617

7000 7500 8000 8500

m/z

Au25SBB18

Au25PET18

Au25PET18: BBSH

1: 5

Au25PET18: BBSH

1: 3

(A)

Cluster 2

Cluster 2:BBSH

1: 5

Cluster 2:BBSH

1: 3

Au25PET18

Au25SBB18

Au25PET15(SBB∩CD-Na)3

(B)

Au25PET13S3(SBB∩CD-Na)2

Au25PET18-xSBBx

x=1 to 17


Figure S22. MALDI (L) mass spectra of bare Au25PET18 (A) and BBSH∩CD incorporated Au25PET18 QCs (denoted as ‘Cluster 2’ in the figure) (B) with excess BBSH thiol. In the case of Au25PET18 with excess BBSH (A), peaks corresponding to various ligand exchanged species, Au25PET18-xSBBx (where x=0 to 17) separated by m/z 42 due to the exchange of PET (MW 137.2) for BBS (MW 179.3), are seen under various conditions (labelled in figure). Spectrum corresponding to bare Au25SBB18 is also shown for comparison (blue trace in A). For (B), various amounts of BBSH was added to ‘Cluster 2' which is a mixture of Au25PET18 and BBSH∩CD incorporated Au25PET18 QCs. While Au25PET18 ligand exchanges completely with BBSH to give a peak at m/z 8152 corresponding to Au25SBB18 (marked on the graph), peaks due to Au25PET15(SBB∩CD-Na)3 and Au25PET13S3(SBB∩CD-Na)2 do not show any shift and their relative intensities are unaffected indicating the absence of ligand exchange.

26

Adamantane thiol

Au25SBB18

Au25SBB18∩CDx

+

+

0.00 0.05 0.100

30

60

90

% L

um

inescen

ce In

ten

sit

y

Vol. of Adamantane thiol added (mL)

Au25

BBS18

Au25

BBS18

+ CD

400 600 800

0.5

1.0

Ab

sorb

ance

Wavelength (nm)

Au25

BBS18

Vol. of Adamantanethiol added

0.025 mL

0.1 mL

450 600 750 900

0.3

0.6

Ab

sorb

ance

Wavelength (nm)

Au25

BBS18

+CD

Vol. of Adamantanethiol added

0.025 mL

0.1 mL

600 750 900

A

bso

rba

nce

% L

um

ine

sce

nce

In

ten

sity

Wavelength (nm)

400 600 8000.00 0.05 0.10

0.5

1.0

Vol. of adamantanethiol added (mL)

600 750 900

600 750 900450

Wavelength (nm)

Ab

sorb

an

ce

Au25SBB18 (blank)

Vol. of AdT added

0.025 mL

0.1 mL

Au25SBB18 ∩CDx (blank)

Vol. of AdT added

0.025 mL

0.1 mL

AdT

Au25SBB18 + Au25SBB18∩CDx + AdT∩CD

(A)

(B) (C)

(D)

Au25SBB18

Au25SBB18∩CDx


Figure S23. Effect of 1-adamantanethiol (AdT) on both Au25SBB18 and Au25SBB18∩CDx was studied. Schematic of the possible events upon addition of AdT are depicted in (A). Luminescence from the QCs upon AdT addition is compared in (B). UV-vis absorption spectra of Au25SBB18 (C) and Au25SBB18∩CDx (D), with addition of AdT are also shown. Re-appearence of Au25 absorption features with 0.1 mL of AdT (green trace, marked with an arrow) in Au25SBB18∩CD is observed in the expanded region of (D).

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