Bulky Surface Ligands Promote Surface Reactivities of [Ag141X12(S-Adm)40] 3+ (X=Cl, Br, I) Nanoclusters: Models for Multiple-Twinned Nanoparticles

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1 Supporting information for Bulky Surface Ligands Promote Surface Reactivities of [Ag141X12(S-Adm)40] 3+ (X=Cl, Br, I) Nanoclusters: Models for Multiple-Twinned Nanoparticles Liting Ren, 1 Peng Yuan, 1 Haifeng Su, 1 Sami Malola, 2 Shuichao Lin, 1 Zichao Tang, 1 Boon K. Teo, 1* Hannu Häkkinen, 2* Lansun Zheng, 1 Nanfeng Zheng 1* 1 Collaborative Innovation Center of Chemistry for Energy Materials, State Key Laboratory for Physical Chemistry of Solid Surfaces, and Department of Chemistry,College ofchemistry and Chemical Engineering, Xiamen University, Xiamen , China 2 Departments of Physics and Chemistry, Nanoscience Center, University of Jyväskylä, FI Jyväskylä, Finland Experimental Details Reagents: Silver nitrate (AgNO3, analytical grade), tetraphenylphosphonium bromide (PPh4Br, 98%), tetraphenylphosphonium chloride (PPh4Cl, 98%), tetraphenylphosphonium iodide (PPh4I, 98%), tert-butyl mercaptan (C4H10S, 97%), phenylacetylene (PhC CH, 98%) were purchased from Alfa Aesar Chemical Reagent Co. Ltd. 1-Adamantanethiol (C10H16S, purity 95%), sodium borohydride (NaBH4, purity 98%), dichloromethane (CH2Cl2, analytical grade) and methanol(ch3oh, analytical grade) were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). The water used in all experiments was ultrapure. All reagents were used as received without further purification. Synthesis of [Ag141X12(S-Adm)40] 3+ clusters: The synthesis of [Ag141X12(S-Adm)40] 3+ nanocluster involves chemical reduction of metal precursors (such as, AgNO3) by an aqueous NaBH4 in the presence of S-Adm and PPh4X (X= Cl, Br, I) in a mixed solvent of dichloromethane and methanol in an ice bath. Synthesis of [Ag141Br12(S-Adm)40] 3+ clusters: In a typical experiment, AgNO3 (60mg, 0.35mmol) was dissolved in a mixed solvent of dichlomethane and methanol at 0 C. Then, adamantanethiol (15 mg, 0.09 mmol) and tetraphenylphosphonium S1

2 bromide (12 mg, 0.03 mmol) were added and stirred vigorously. After 20-min stirring, 1mL NaBH4 aqueous solution (45 mg/ml) and 50 ul triethylamine were added quickly under vigorous stirring. The reaction was aged for 12 h at 0 C. The aqueous phase was then removed and the mixture in organic phase was washed several times with water. The crystals were grown from a dichloromethane solution placed in a closed container with toluene. Dark green rhombic crystals were obtained in a week. Yield~20% based on AgNO3. Physical measurements: UV-Vis absorption spectra were recorded on a Shimadzu UV-2550 Spectrophotometer with dichloromethane as solvent. The absorption coefficient of [Ag141Br12(S-Adm)40] 3+ clusters at 460 nm was measured to be M -1 cm -1. Mass spectra were recorded on an Agilent Technologies ESI-TOF-MS. TEM studies were performed on a TECNAI F-30 transmission electron microscope operating at 300 kv. Single-Crystal Analysis: The diffraction data were collected on an Agilent SuperNove X-Ray single crystal diffractometer using Mo Kα (λ= Å) micro-focus X-ray sources at 100 K. The data were processed using CrysAlisPro. 1 The structure was solved and refined using Full-matrix least-squares based on F 2 with program SHELXS-97 and SHELXL-97 2 within OLEX2. 3 Crystallographic data: orthorhombic Pbcn, a = (6) Å, b = (6) Å, and c = (7) Å, α=90, β=90, γ=90, V= (17) Å 3, Z=4, Mo Kα, T=100K, 2θmax=54.960, reflections were measured, of which were unique with Rint= Final R1= 8.64%, wr2= for 2825 parameters and reflections with Ι>2σ(Ι). Ligand exchange with phenylacetylene (PAH) and tert-butyl thiol (TBSH): To a 1 ml CH2Cl2 solution of [Ag141Br12(S-Adm)40] 3+ or [Ag141Cl12(S-Adm)40] 3+ (5mg, 2x10-4 mmol) was added exchange ligands (PAH or TBSH) in varying proportions. After stirring for 0.5 h at room temperature, hexane was added to precipitate out the Ag nanoparticles. The solid products were separated by centrifugation, washed three times with water, then dissolved in 1 ml CH2Cl2 for ESI-MS meaurements. Ligand exchange with mercaptosuccinic acid: To a 1 ml ethanol suspension of [Ag141Br12(S-Adm)40] 3+ (5 mg, mmol) was added mercaptosuccinic acid S2

3 (0.4mg, mmol). After stirring overnight at room temperature, concentrated ammonia ( mmol) was added to precipitate out the Ag nanoparticles. The solid products (hereafter referred to as MSA-exchanged 1) were separated by centrifugation, washed three times with ethanol, and dissolved in deionized water for UV-vis meaurements. DFT calculations: We used the real space grid code-package GPAW. 4,5 Experimental crystal structure with true S-Adm ligands and Br-anions was used as a starting point for all of the calculations. All the structures were relaxed using PBE-functional, Å grid spacing and 0.05 ev/å force criterion for the residual forces. The energy minimized structure follows closely the crystal data. The idealized principal moments of inertia were calculated both from the crystal structure data and from the computationally optimized structure; the results for the crystal structure are amu Å 2, amu Å 2 and for the computationally relaxed structure amu Å 2, amu Å 2. These values (two higher, degenerate values, and one lower value) are consistent with the slightly prolate shape of the nanoparticle. The Ag-Ag atomic distances in the inner Ag19 IBI were found to be: central-central Å; central-peripheral Å; and peripheral-peripheral Å. The average Ag-S bond distance at the metal-ligand interface is Å, and the Ag-Br distances fall into two classes: Å at the C5 axis and Å elsewhere. Superatom states were analyzed by projecting the Kohn-Sham wave functions to the spherical harmonics with respect to the center of the mass of the cluster. 7 Optical spectra were calculated with 0.25 Å grid spacing using linear response time-dependent density-functional theory (LR-TDDFT). The continuous spectra were plotted using a 0.1 ev Gaussian smoothing of the individual oscillator strengths. The plasmonic peak was analyzed using the so-called transition contribution map (TCM) that is based on time-dependent density functional perturbation theory (TD-DFPT). 8 In addition to TCM, the induced density was analyzed to reveal the nature of electron oscillations of the plasmon peak. S3

4 Figure S1. Electrospray ionization (ESI) mass spectra (MS) of [Ag141Br12(S-Adm)40] 3+. (a) High-resolution spectrum; (b) Spectrum with a wide mass range. The surface bromide ligands on the cluster were replaced by chlorides (presumably from CH2Cl2) during the measurement. S4

5 Figure S2. The packing diagram of [Ag141Br12(S-Adm)40] 3+ (1) in the orthorhombic unit cell of Pbcn space group (Z=4). Color legend: green, Ag; yellow, S; claret-red, Br. All carbon and hydrogen atoms are omitted for clarity. Figure S3. TEM images of the title cluster 1. The solids were dissolved in CH2Cl2 and dispersed onto Cu grid in the preparation of TEM samples. S5

6 Figure S4. The left- and right-handed enantiomers of the Ag19 core of 1 resulted from a twist about the principal fivefold symmetry axis. S6

7 Figure S5. The binding modes of Br and S ligands on the surface Ag70 shell of 1. Color legend: green, Ag; yellow, S; claret-red, Br; grey, C. All hydrogen atoms are omitted for clarity. S7

8 Figure S6. The van der Waals representation of the two pentagonal Ag5(S-Adm)5 rings with (right) and without (left) the halide ligands, showing that the two polar sites (on the idealized principal fivefold symmetry axis) are capable of hosting the halide ligands. Color legend: green/blue, Ag; yellow, S; claret-red, halide; grey, C. All hydrogen atoms are omitted for clarity. Figure S7. ESI-MS of [Ag141Cl12(S-Adm)40] 3+ in CH2Cl2 showing the main m/z peak at 7441 for [Ag141Cl12(S-Adm)40] 3+ and an impurity peak at for [Ag141Cl13(S-Adm)39] 3+. S8

9 Figure S8. ESI-MS of [Ag141l12(S-Adm)40] 3+ in CH2Cl2 showing m/z peaks between 7850 and 7700, corresponding to [Ag141I12-nCln(S-Adm)40] 3+ where n=0-3, respectively. Figure S9. Calculated projected density of the electron states on spherical harmonics for [Ag141Br12(S-Adm)40] 3+ nanoparticle. Inset figure shows a zoom-in view of the states close to zero energy that corresponds to the HOMO state energy. The gap around 0.15 ev matches with 86 electrons in the Jellium electron count. S9

10 Figure S10. Level scheme of the electronic states close to the HOMO energy (E=0) of the [Ag141Br12(S-Adm)40] 3+ cluster. The numbers in the scheme indicate the free-electron counts after each level. On the right, the two almost-degenerate levels are magnified and electron occupancies for 1+ and 3+ states of the cluster are shown. Figure S11. UV-Vis spectra of toluene solution of Ag141Br12(S-Adm)40 heated in air at 50 C for different time intervals. S10

11 Figure S12. Calculated optical absorption spectra for [Ag141Br12(S-Adm)40] 3+ (in blue) and [Ag141Br12(S-Adm)40] + (in red). Spectra have been shifted from each other vertically for better visualization. The spectra have been broadened using Gaussians (0.1eV broadening) for individual transitions. S11

12 Figure S13. Transition contribution map (on the left) and the total induced density (on the right) analyzed computationally for the plasmonic peak at 406nm. Bright yellow spots in the 2D-map correspond to the strongest contributions of transitions from the occupied states (lower left panel) to the unoccupied states (upper right panel). The lower right panel shows the calculated absorption spectrum in which the analyzed peak is marked with arrow. Figure S14. The special S atoms (marked in pink) with longer-than-normal Ag-S bonds (bond lengths in Å) in the middle layers of 1. S12

13 Figure S15. ESI-MS of [Ag141Cl12(S-Adm)40] 3+ after ligand-exchange with tert-butyl mercaptan (TBSH) to give [Ag141Cl12(S-Adm)40-n(SR)n] 3+ where n=0-14 and SR = SC4H9. Figure S16. UV-Vis of [Ag141Br12(S-Adm)40] 3+ nanoparticle in ligand-exchange with mercaptosuccinic acid. before and after S13

14 Figure S17. Photographs of the solution of [Ag141Br12(S-Adm)40] 3+ nanocluster (1) after ligand-exchange with mercaptosuccinic acid. (a) ethanol solution, the molar ratios of MSA : 1 used in the ligand exchange are 4:1 (left) and 12:1 (right); (b) the corresponding aqueous solution after exchange reactions for 8h. Figure S18. Photographs of the solution of [Ag136(SR)64Cl3Ag0.45] - nanocluster after ligand-exchange with mercaptosuccinic acid. (a) ethanol solution, the molar ratios of MSA : Ag136 used in the ligand exchange are 4:1 (left) and 12:1 (right); (b) the corresponding aqueous solution after exchange reactions for 8h, showing no solubilities in water as a result of no thiolate ligand exchange. S14

15 Table S1. The thiolate coverage on thiolated metal nanoparticles as a ratio of the number of surface thiolates (B) to the surface metal atoms (A). Cluster Composition Number of surface Ag atoms (A) Number of surface SR ligands (B) Surface Thiolate Coverage (B/A) Surface Ligand Coverage Ag141 Ag141Cl12(S-Adm) Ag136 Ag136(SR)64Cl3Ag Ag374 Ag374(SR)113Br2Cl Reference: 1) CrysAlis, P. Agilent Technologies, Yarnton, England ) Sheldrick, G. M. Acta crystallographica. Sect. A, 2008, 64, ) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. J. Appl.Crystallogr. 2009, 42, ) Mortensen, J. J.; Hansen, L. B.; Jacobsen, K. W. Phys. Rev. B 2005, 71, ) Enkovaara, J.; Rostgaard, C.; Mortensen, J. J.; Chen, J.; Dułak, M.; Ferrighi, L.; Gavnholt, J.; Glinsvad, C.; Haikola, V.; Hansen, H. A.; Kristoffersen, H. H.; Kuisma, M.; Larsen, A. H.; Lehtovaara, L.; Ljungberg, M.; Lopez-Acevedo, O.; Moses, P. G.; Ojanen, J.; Olsen, T.; Petzold, V.; Romero, N. A.; Stausholm-Møller, J.; Strange, M.; Tritsaris, G. A.; Vanin, M.; Walter, M.; Hammer, B.; Häkkinen, H.; Madsen, G. K.H.; Nieminen, R. M.; Nørskov, J. K.; Puska, M.; Rantala, T. T.; Schiøtz, J.; Thygesen, K. S.; Jacobsen, K. W. J. Phys. Condens. Matter. 2010, 22, ) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996, 77, ) Walter, M.; Akola, J.; Lopez-Acevedo, O.; Jadzinsky, P. D.; Calero, G.; Ackerson, C. J.; Whetten, R. L.; Grönbeck, H.; Häkkinen, H. Proc. Natl. Acad. Sci. 2008, 105, ) Malola, S.; Lehtovaara, L.; Enkovaara, J.; Häkkinen, H. ACS Nano 2013, 7, S15