Crystal Structure of Faradaurate-279: Au279(SPh ... - ACS Publications

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Cite This: J. Am. Chem. Soc. 2017, 139, 15450-15459

Crystal Structure of Faradaurate-279: Au279(SPh‑tBu)84 Plasmonic Nanocrystal Molecules Naga Arjun Sakthivel,† Shevanuja Theivendran,† Vigneshraja Ganeshraj,† Allen G. Oliver,‡ and Amala Dass*,† †

Department of Chemistry and Biochemistry, University of Mississippi, Oxford, Mississippi 38677, United States Department of Chemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States

‡

S Supporting Information *

ABSTRACT: We report the discovery of an unprecedentedly large, 2.2 nm diameter, thiolate protected gold nanocrystal characterized by single crystal X-ray crystallography (sc-XRD), Au279(SPh-tBu)84 named Faradaurate-279 (F-279) in honor of Michael Faraday’s (1857) pioneering work on nanoparticles. F-279 nanocrystal has a core−shell structure containing a truncated octahedral core with bulk face-centered cubic-like arrangement, yet a nanomolecule with a precise number of metal atoms and thiolate ligands. The Au279S84 geometry was established from a low-temperature 120 K sc-XRD study at 0.90 Å resolution. The atom counts in core−shell structure of Au279 follows the mathematical formula for magic number shells: Au@Au12@Au42@Au92@Au54, which is further protected by a final shell of Au48. Au249 core is protected by three types of staple motifs, namely: 30 bridging, 18 monomeric, and 6 dimeric staple motifs. Despite the presence of such diverse staple motifs, Au279S84 structure has a chiral pseudo-D3 symmetry. The core−shell structure can be viewed as nested, concentric polyhedra, containing a total of five forms of Archimedean solids. A comparison between the Au279 and Au309 cuboctahedral superatom model in shell-wise growth is illustrated. F-279 can be synthesized and isolated in high purity in milligram quantities using size exclusion chromatography, as evidenced by mass spectrometry. Electrospray ionization-mass spectrometry independently verifies the X-ray diffraction study based heavy atoms formula, Au279S84, and establishes the molecular formula with the complete ligands, namely, Au279(SPh-tBu)84. It is also the smallest gold nanocrystal to exhibit metallic behavior, with a surface plasmon resonance band around 510 nm.

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cules.13,14 For instance, an alkanethiolate protected nanomolecule series15−25 comprises of Au25(SR)18, Au38(SR)24, Au 6 7 (SR) 3 5 , Au 1 3 0 (SR) 5 0 , Au 14 4 (SR) 6 0 , Au 3 2 9 (SR) 8 4 , Au∼500(SR)∼120, and Au∼940 ± 20(SR)∼160±4. These nanomolecules offer the unique opportunity to probe into factors influencing the evolution from molecular to metallic behavior in nanoparticles. Evolution in size can be traced using optical and electrochemical behaviors. Small nanomolecules (such as Au25(SR)18, Au38(SR)24, Au36(SR)24, Au30(SR)18, etc.)15,26−29 exhibit unique discrete electronic transitions, whereas plasmonic gold nanocrystals have an optical plasmon band around 500−530 nm.7,24,25 Likewise, smaller Au nanomolecules have an electrochemical gap.30,31 Larger nanomolecules exhibit quantized double layer charging in electrochemical studies indicative of metal−electrolyte interface.30,32−35 In ultrafast electron dynamic studies, molecular-like particles do not show pump-power-dependent transients, but the plasmonic metallike particles exhibit pump-power-dependent properties and have plasmon bleach.36−40 With an increasing number of applications employing Au NPs, crystal structure determination of those Au NPs is highly

INTRODUCTION Gold nanoparticles (Au NPs) are engineered for different applications in nanomedicine,1,2 imaging,1 sensors,3 electrocatalysis,4 and solar cells.5 Au NPs in 3−100 nm size range have some degree of polydispersity in size. But thiolate protected Au NPs, whose diameter is smaller than 3 nm, offer highly stable discrete sizes with atomic precision (±0 atoms), hence termed as “nanomolecules”.6−9 Revolutionary work in two-phase synthesis of thiol derivatized Au NPs by Brust et al. led to the intense interest in the ultrasmall (1−3 nm) Au NPs.10 Concurrent work by Whetten et al. on molecular-like gold nanocrystals with different core sizes ranging from ∼116−459 Au atoms laid the groundwork for atomically precise Au NP research.6 Pioneering work by Kornberg et al.11 in the X-ray crystallographic structure determination of Au102(S-C6H4COOH)44 provided clarity and insight into structural arrangement of metal−ligand self-assembly interface and led to the resurgence in structural determination of atomically precise Au NPs. Subsequently, several crystal structures have been reported revealing several new kernels and staple assemblies that govern the stability of those nanomolecules.9,12 Ligand stereochemistry and electronics dictate the core size formation; therefore, each type of ligand has a unique series with discrete sizes in thiolate protected gold nanomole© 2017 American Chemical Society

Received: August 14, 2017 Published: October 9, 2017 15450

DOI: 10.1021/jacs.7b08651 J. Am. Chem. Soc. 2017, 139, 15450−15459

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Journal of the American Chemical Society

of minute gold particles to manipulate light−matter interactions.58 Other Faradaurates include F-329, F-500, and F940.7,24,25 Herein, we report: (a) the structure of the largest gold nanocrystal characterized by single crystal X-ray crystallography that has a molecular formula of Au279(SPh-tBu)84; (b) the synthesis and isolation of pure samples in milligram quantities of Au279(SPh-tBu)84 nanocrystal; and (c) mass spectrometric characterization and optical absorption properties of the Au279 gold nanocrystal. Au246(p-MBT)80 (core size 2.2 nm) is molecular in behavior,51 whereas in Au279(TBBT)84 with a mere increment of 33 Au atoms and 4 ligands exhibits surface plasmon resonance in an unprecedented manner. Au279 is the smallest thiolate protected Au NP to exhibit metallic behavior.

desired to understand their properties. However, growing single crystals for structural determination is still seemingly a daunting task. It has been reported that the challenge of growing single crystals can be overcome by employing rigid and bulky ligands.41 Maran et al. have reported an electrochemical route to obtain quality single crystal of thiolate protected Au nanomolecules in a reproducible manner.42 Owing to the rigidity and bulkiness of the 4-tertbutylbenzenethiolate (TBBT) ligand, the TBBT protected gold nanomolecule series is one with the highest number of crystal structures for different sizes, viz. Au28(SR)20, Au36(SR)24, Au 44 (SR) 28 , Au 52 (SR) 32 , Au 92 (SR) 44 , Au 133 (SR) 52 , and Au279(SR)84, where SR is TBBT ligand.41,43−46 Au28, Au36, Au44, Au52, and Au92 TBBT protected gold nanomolecules have face-centered cubic (fcc) kernels, in contrast with the Au25 and Au38 alkanethiolate series, which have noncrystalline icosahedral (Ih) cores.15,17 Although the above-mentioned five kernels have an fcc arrangement, they are not metallic and have discrete electronic transitions and an optical band gap. Unlike other sizes in the TBBT series, Au133 has a noncrystalline icosahedral core and is also molecular-like with a broad optical absorption at ∼500 nm reminiscent of emergent surface plasmon resonance. Au36 and Au133 are remarkably stable among the molecular-regime TBBT protected nanomolecules and can be synthesized in large quantities.45,47−49 Although the crystal structures of Au28, Au44, Au52, and Au92 have been reported, they are not stable under etching conditions, unlike Au36 and Au133, and could not be isolated in significant quantities. Another case of a rigid aromatic ligand protected series of Au nanomolecules is the para-methylbenzenethiol (p-MBT). Jin et al. have reported the crystal structure of Au130(p-MBT)5050 and Au246(p-MBT)8051 nanomolecules with an inodecahedron core. Au130 has an inodecahedron core and quasi-D5h symmetry, whereas Au133 has an icosahedron core, and complete Au133(TBBT)52 structure has no symmetry. Both Au130 and Au133 have isomeric Au13 and Au55 core−shells. Au130(pMBT) 50 has optical absorption spectra similar to Au130(SC2H4Ph)50.20 Au246(p-MBT)80, the next size in the pMBT series, is not metallic, and it has no SPR band, but has absorption features at 400, 470, and 600 nm. The crystal structures of larger Au nanomolecules such as Au102, Au103, Au246 - decahedra,11,51,52 Au130 - inodecahedra,50 and Au133 icosahedra41,45 are all multiply twinned particles (MTPs), and Au146 - singly twinned anticuboctahedron,53 and lack a true metallic fcc. Pioneering works on crystallography of other noble metal nanocrystals include icosahedral Pd145 and PtPd164 by Dahl et al.,54,55 icosahedral Ag216 by Mak et al.,56 and TBBT protected plasmonic five-fold twinned decahedral Ag136 and Ag374 by Zheng et al.57 Several unanswered questions still remain: What is the next size in the TBBT series? Is it metallic or molecular? Does it have an icosahedral core similar to Au133 or a bulk fcc-like core? At what size will the mutiple twinning in particles converge to relaxed bulk fcc? Is it atomically precise and plasmonic as with Au329(SR)84 or plasmonic but not a nanomolecule like Au∼500±10(SR)∼120±3? To answer these questions, we have synthesized and crystallized the Faradaurate Au279(TBBT)84 nanocrystal using a bottom-up methodology. F-279 is the next ultrastable size in the TBBT series. Faradaurate nanocrystals7 are a class of Au NPs, which are monodisperse, highly stable and plasmonic, thiol-derivatized gold nanocrystals named in honor of Michael Faraday, who was the first to report the ability

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RESULTS AND DISCUSSION Crystallography. The heavy atom molecular formula, Au279S84 was established from low-temperature X-ray diffraction study. Au279S84 consists of a central Au atom surrounded by four concentric shells, containing 12 atoms (shell 1), 42 atoms (shell 2), 92 atoms (shell 3), and 102 atoms (shell 4). The metal core consists of cuboctahedral Au13, cuboctahedral Au55, cuboctahedral Au147, truncated octahedral Au201, and a truncated octahedral variant Au249. The Au249 core is protected by 6 dimeric [-SR-Au-SR-Au-SR-] staples, 18 monomeric [-SRAu-SR-] staples, and 30 bridging [-Au-SR-Au-] ligands, leading to the total heavy atom composition, Au 279 S 84 . This composition was independently verified by ESI mass spectrometry, vide infra, and its molecular formula was established as Au279(SPh-tBu)84. Core−Shell Structure Au13, Au55, and Au147 Cuboctahedrons in Au279S84. Crystal structure of Au279S84 nanocrystal containing a cuboctahedron (CO) core−shell structure in a fcc arrangement is shown in Figure 1. Au279 nanocrystal has a centered Au13 CO core, an Au central atom with 12 neighboring Au atoms along the vertices of a CO (Au@Au12) (Figure 1a). The cuboctahedron is one of the 13 Archimedean solids and it has 12 vertices, 8 triangular {111} facets, and six square {100} facets with 24 edges. Au@Au12 is followed by Au42 and Au92 CO shells (Figure 1b,c). Au279 nanocrystal has 3 perfect CO shells forming Au147 (Au@Au12@Au42@Au92) magic number core−shell structure. Au55 (Au@Au12@Au42) CO core−shell in Au279 is a steroisomer of Au55 icosahedron core−shell structure found in Au133. The magic numbers of the Au147 cuboctahedron core−shell follows the equation N(n) = (2n − 1)[5n(n − 1) + 3]/3, and S(n) = 10n2 + 2, where N(n) is the number of atoms, S(n) is the surface atoms in respective shell, n is the number of surface atoms in respective shell, and n is the number of concentric shells.59,60 For example, when n = 1−5, the magic numbers of concentric shells are 1, 13, 55, 147, and 309 and with 12, 42, 92, and 162 surface atoms, which is identical to the concentric icosahedral shells but with different packing. Au102 Fourth Shell, Au201 Truncated Octahedron (TO), Geometric Relevance of TO, and Au249 TO+ Core of Au279. In an ideal Au309 structure, the Au147 would be protected by a shell of 162 surface atoms to give a total of 309 atoms. In the Au279 nanocrystal, the outer shell of Au147 is not protected by a perfect 162 atom CO shell. Instead, each square {100} facet has 9 Au atoms (Figure 1d, magenta atoms) arranged over the octahedral holes of {100} facets in Au147 CO core, adding up to 54 Au atoms. This forms a perfect Au201 truncated octahedron (TO 201). The perfect Au201 TO follows the magic 15451


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Figure 1. X-ray crystallographic atomic structure of Au279S84 gold nanocrystal core of Au279(SPh-tBu)84. First and second row shows the front and side views, respectively. (a) Au13: Centered (cyan) Au12 atom cuboctahedra (CO) core (blue). (b) Au42 atom CO shell (orange). (c) Au92 atom CO shell (green). (d) Au201 truncated octahedron structure with 9 Au atoms (magenta) arranged on 6 square facets {100} (green) of CO Au147. (e) 6 Au atoms (red) arranged on the 8 {111} facets of Au201. (f) Au279S84 structure with ligand shell; yellow, S; blue, monomeric Au; and orange, dimeric Au. (g) Au249: Au147 with breakdown of Au102 outer shell made up of 6 square facets with 9 atoms, 2 symmetric triangles on the poles, and 6 asymmetric triangles arranged on the body. (h) Core−shell structure of Au279S84. Ball and stick view is shown in Figure S1.

number equation for TO, that is, N = 16n3 + 15n2 + 6n + 1, where n = 2.59 Au201 TO structure (Figure 1d) is equivalent to truncating 3 edge atoms on all 24 edges (72 atoms), 12 vertex atoms, and 8 triangular {111} facets (24 atoms) from the Au309 superatom model. It is also equivalent to symmetrically truncating 5 atoms (or 2 layers) along the six vertices of a Au231 octahedral (Oh) superatom model.60,61 Further, on the TO 201 core, 48 atoms are arranged on the 8 {111} facets with 6 Au atoms on each face, forming “Au249 atom core” (Au@Au12@Au42@Au92@Au54@Au48) (Figure 1e,g). There are two types of 6 Au atom triangular layer additions on {111} facets of TO 201, namely: 2 symmetric and 6 asymmetric triangles. The 2 symmetric triangles are added on either pole of the TO 201 (Figure 1g). The remaining 6 asymmetric triangular faces are arranged over {111} facets on the body of the TO 201 (Figure 1g). This type of addition to the {111} facets of TO leads to the TO+ 249 structure with reentrant grooves along the edges adjoining {100} and {111} facets (Figure 1e−g). Total structure of Au279S84 is shown in Figure 1f,h. Complementary View of Au249 TO+ Core−Shell Structure as Nested Polyhedra. The centered Au13 CO (Schläfli symbol: r{4,3}) is encapsulated by Au42 CO shell

(Figure 2). The Au42 CO shell can be viewed as Au30 rhombicuboctahedron (rr{4,3}) nested in Au12 CO (i.e., Au30@Au12) (Figure 2b,c). Next the Au92 shell can be viewed as an Au80 great rhombicuboctahedron (tr{4,3}) nested in Au12 CO (Figure 2d,e). Au54 atoms of 102 atom outer shell can be viewed as a Au54 TO (t{3,4}) (Figure 2f). The remaining 48 atoms on the {111} facets of TO+ 249 forms a distorted truncated cube (t{4,3})) (i.e., Au54@Au48) (Figure 2g). The distortions in the form of elongated square (i.e., rectangle) faces in rhombicuboctahedron and great rhombicuboctahedron (Figure 2b,d) keeps them from being the ideal Archimedean solids. In total, there are 5 forms of Archimedean solids, namely: cuboctahedron, rhombicuboctahedron, great rhombicuboctahedron, truncated octahedron, and truncated cube, nested in the Au249 core. Alvarez and Dahl et al. have beautifully presented a similar nested-core−shell structure for icosahedral Pd145 and PtPd164 clusters, respectively.55,62 Ligand Shell Protecting the Au249 Core and Surface Patterns. The complete structure of Au279S84 comprises a Au249 core and ligand shell with 3 types of staple motifs viz. bridging (30 S), monomeric (18 AuS2), and dimeric (6 Au2S3) staples (Figures 1f and 3). The bridging ligands and monomeric staple motifs of the ligand shell can be classified into two types, 15452


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Figure 2. Nested Archimedean polyhedral shells in Au249 TO+ core−shell structure. (a) Au13: Centered (cyan) Au12 atom cuboctahedral (CO) core (blue). (b) Au30 rhombicuboctahedron nested in (c) Au12 CO forms the Au42 atom CO shell (orange). (d) Au80 great rhombicuboctahedron nested in (e) Au12 CO forms Au92 atom CO shell (green). (f) Au54 truncated octahedron (TO) and (g) Au48 distorted truncated cube (d-TC) form the Au102 shell. Some bonds in (a), (b), (d), (f), and (g) are excluded for clarity; refer to Figure S2 with all bonds.

Triple Helix Surface Pattern. In Figure 3g, the red Au atoms bound by bridging ligands, along with the monomeric blue Au located on distorted {111} facets on body forms a four stepladder-like triple-helix assembly pattern on the nanocrystal. The triple-helix assembly is color coded (red, orange, and blue) to reveal that the helix begins from one vertex atom on one {111} faceted pole and terminates near an equivalent vertex Au atom of {111} facet on the other pole; top and side views are shown in Figure 3h,i, respectively. Symmetry Reduction from High Symmetry Octahedral Point Group TO 201 Core−Shells to Chiral, PseudoD3 Point Group F-279. A cuboctahedron has an octahedral point group with 16 proper axes of rotation (3 C4, 4 C3, and 9 C2), 7 improper axes (4 S6 and 3 S4), 9 planes (3 σh and 6 σd), and an inversion center. Up to three shells, that is, Au147 CO, have the Oh point group. In the fourth shell, the Oh symmetry is retained in TO 201 and up to the addition of two symmetric triangles to {111} facets. Addition of the asymmetric triangles on 6 {111} facets and the ligand shell reduces the symmetry of the Au279S84 structure to a chiral, pseudo-D3 point group. The principal C3 rotational axis passes through the poles via the central atom (symmetric triangles) of the nanocrystal (Figures 3c and S3). The three perpendicular C2 axes passes through the 3 vertices of TO+ core via the central atom, at the equatorial position of the nanocrystal protected by dimeric staples (Figures 3e and S3). Shell Growth Pattern in Au249 TO+ Core of Au279S84 Nanocrystals and Its Comparison with Naked Au309 CO Model. The shell growth of Au279 nanocrystal takes place in three modes of packing: (1) ABCAC packing along two {111} facets on the poles of the nanocrystal (Figure 4a); (2) the remaining six {111} facets on the body takes ABCA packing mode for the first three shells, followed by a hybrid packing (Figure 4b); and (3) along the six {100} square facets the packing follow the ABABA mode (Figure 4c). Growth Along {111} Facets on the Poles. Poles of the TO+ 249, with symmetric triangles, follow ABCAC arrangement.

namely: intrafacet (24 S and 6 AuS2) and interfacet (6 S and 12 AuS2) ligands/staples. The 14 faceted polyhedron, TO+ Au249, can be viewed as a structure with triangular {111} facets on the two poles (symmetric triangular faces), and the remaining 6 square {100} and 6 triangular {111} facets are split equally into 3 square and 3 triangular facets arranged in an alternating fashion on 2 halves of the body with 2 squares and 2 triangles meeting at all vertices (Figures 1e and 3). Ligand Shell on {100} Facets. Each {100} square facet on the body of Au279 nanocrystal has 9 Au atoms, in a 3 × 3 matrix arrangement. Six of the 9 Au atoms in the {100} square facets are protected by 3 intrafacet bridging ligands. The remaining 3 Au atoms are anchored by one interfacet bridging ligand connecting the neighboring {111} facet on the same half of the body, one monomeric staple to the {111} facet on the pole, and one dimeric staple connecting to the {111} facet on the other half of the body (Figure 3a). Ligand Shell on {111} Facets. The 6 {111} triangular facets on the body have one intrafacet bridging ligand, one intrafacet monomeric staple, and one monomeric staple anchoring the {111} facet on the pole (Figure 3b). Hence, one monomeric staple from each of the alternating {111} and {100} facets from each half of the body anchors 6 Au atoms on the poles in a propeller blade type arrangement (Figure 3c). Assembly of Staple Motifs on the TO+ 249 Core. Two types of monomeric staples protecting the nanocrystal namely: 6 intrafacet monomeric staples on body of the nanocrystal (1 on each {111} facet on body) and 12 interfacet monomeric staples on the poles (6 on each pole). Figure 3e shows the 6 dimeric staples, one from each {100} facet on one-half to {111} facet on the other half of the nanocrystal, suturing one-half to the other and protecting the grooves on the equator, while the monomeric staples protect both poles. Two types of bridging ligands in Au279 are shown in Figure 3f, that is, three intrafacet bridging ligands on {100} facets, one intrafacet on {111} facets, and one interfacet ligand bridging adjoining {100} and {111} facets. 15453


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Figure 3. Staple motif modes of protecting the Au249 core. (a) Six {100} square facets of the nanocrystal are protected by 3 intrafacet bridging ligands, one interfacet bridging ligand, and one monomeric and one dimeric staple. (b) Six {111} triangular facets on the body of the nanocrystal are protected by one intrabridging ligand and two monomeric and one dimeric staples. (c) Two {111} facets on poles of the nanocrystal are protected by 6 monomeric ligands, with 3 anchoring square facets and 3 anchoring triangular facets. (d) 18 monomeric staples: 6 staples protecting each pole of the nanocrystal and one monomeric staple on each {111} facet on the body. (e) Dimeric staples suturing two halves of the body and monomeric staples anchoring the poles to body. (f) Bridging ligands protecting {100} (yellow ball) and {111} (yellow wire) facets on body. (g) Au bound to the bridging ligands (red ball) on {111} facets forms a 4 stepladder-like arrangement with monomeric Au (blue). (h) Front view of three ladder-like helical arrangement. In total there are 30 bridging ligands [-Au-S-Au-], 18 monomeric staples [-S-Au-S-], and 6 dimeric staples [-S-Au-S-Au-S-]. Yellow, sulfur; blue, monomeric Au; orange, dimeric Au; magenta, square face Au; and red, triangular face Au. Au147 CO is not shown in (d−i) for clarity.

model which has ideal ABCAB packing (Figure 4a,d). In the presence of the ligand shell, only the ABCAC arrangement would allow for the maximum of 6 Au atoms to be packed on

ABCA up to the third shell (Au147 CO) corresponds to typical fcc packing. The C type arrangement as the next layer (TO+) makes it unique to Au279 when compared to the Au309 CO 15454


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Figure 4. Tessellation in shell growth of Au279S84 gold nanocrystal along {111} and {100} facets compared with a Au309 cuboctahedron model. Top row reveals the side view of shell growth pattern, and bottom row shows the front view of respective facets. Cyan, central Au atom; blue, Au12 CO core around the central atom; orange, Au42 shell; green, Au92 shell; magenta, Au atoms on {100} facet of Au102 shell; red, Au atoms on {111} facets of Au102 shell; and yellow, S. Shell wise growth pattern in (a) two symmetric triangular {111} facets in Au279 nanocrystal follows ABCAC stacking, and front view shows the outer C layer (red) eclipsed on inner C layer (orange) and staggered on B layer (blue). (b) Six asymmetric {111} facets in Au279 nanocrystal follow ABCA pattern followed by a hybrid outer layer containing an arrangement of C (4 red atoms) and B (2 red atoms indicated by arrows), monomeric staple Au, blue. (c) Six square {100} facets of Au279 nanocrystal following ABABA pattern similar to Au309 CO model but the outer layer (magenta) of Au279 has only 9 atoms without the edge and vertex atoms compared to complete Au309 CO model. (d) Eight {111} facets of Au309 CO model following ABCAB stacking pattern typical for fcc. (e) Six {100} facets of Au309 CO model follows the pattern ABABA.

the outer layer of the {111} facet. The presence of ligand shell makes it unfeasible to accommodate edge atoms as seen with naked Au309 (Figure 4a,d). Growth Along {111} Facets on the Body. Six {111} facets on the body of F-279 has 6 Au atoms packed in a asymmetric triangular fashion. The distortion is the result of an intrafacet monomeric staple and bridging ligand, on each of the six {111} facet on the body (Figure 4b). The inner three shells follow ABCA mode of shell growth, and in the 6 Au atom, outer layer, 4 Au red atoms are packed in C stacking, and 2 Au red atoms are arranged (indicated by arrows) in B stacking mode (Figure 4b). Growth Along {100} Facets on the Body. Despite the presence of ligand shell, {100} facets in Au279 follow the same packing (ABABA) as the naked Au309 model with missing edge and vertex atoms (Figure 4c,e). The ideal ABABA growth pattern of the nanocrystal corresponds to the fcc TO 201. Comparison between Relaxed Au279 fcc Structure and Multiply Twinned Au133 Structure. Table 1 shows the analysis of bond length (mean, standard deviation (SD), and range) comparison between core−shell Au279S84 and Au133S52 crystal structure data. The noncrystalline Au133 has a significant variability of 0.197 Å in the mean bond length from centered Au13 icoshedron core (Au0-Au1) to Au52 (Au3-Au3) atom outer layer, whereas in the crystalline fcc core of Au279 the variation is narrow. Also, the SD increases rapidly for Au133 (0.008 to 0.073), but in Au279 SD increases gradually. Dahl et al. have reported a similar trend observed in icosahedral Pd145 and Pd164−xPtx clusters, where the mean bond length varies from 13 atom core to outer shell.55 The Au-Au bond length in cubic close packed gold is 2.88 Å; Au279

nanocrystal core has a similar bond length of 2.864 Å which is very relaxed compared with icosahedral Au133 (2.75 Å). Similar phenomena in transformation from multiply twinned icosahedral structures that have noticeable strain to bulk cubiclike packing have been reported.63,64 In the case of Pd cluster with N > 561 atoms, twinned structures converge to relaxed fcc.63,64 Also, TBBT protected Ag374 nanocrystals possess a fivefold twinned structure.57 Therefore, the transition in structure from twinned geometry to relaxed bulk fcc-like structures is element specific. Perhaps, Au279 is the critical size where goldthiolate NPs transform from MTP to metallic particles. Until now, all the sizes smaller than Au279 have twinned structures (Au102, Au103, Au130, Au133, Au146, and Au246) and sizes larger than Au279 have fcc structures (Au329, Au∼500, and Au∼940). In the Au279 nanocrystal, mean bond length for all the four shells, intra- and intershell linkages vary by a very narrow range. In addition, the staple gold atoms in Au279 are closer to the core compared with Au133. The mean bond length and range of Au4Au4 shell linkage is greater compared with the remaining inner shells, because of the difference in packing along the {111} facets of TO 201. Alternate TO+ 243 Core View and a Au Atom Modeled with Partial Occupancy in the Structure. Au279S84 structure can be alternatively viewed as TO+ 243 protected by 18 bridging ligands (solely on {100} facets), 24 monomeric staples, and 6 dimeric staples, that is, the 6 Au red atoms shown in Figure 3g can be considered as monomeric staple gold. A detailed representation of TO+ 243 is given in the SI (Figure S4). The 6 Au red atoms are accounted as part of the core to form TO+ 249, due to their proximity to the Au92 third shell (average bond length from Au92 to 6 red Au atoms = 3. 079 Å) 15455


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Journal of the American Chemical Society Table 1. Comparison of Bond Length in Intra and Intershell Between Au279S84 and Au133S52 Nb

Meanb (Å)

SDb

Range (Å)

Connectivity

279

133

279

133

279

133

279

133

Au0-Au1 Au1-Au1 Au1-Au2 Au2-Au2 Au2-Au3 Au3-Au3 Au3-Au4 Au4-Au4 Au4-Au(st)c Au(st)-S Au4−Sc

12 24 84 96 228 216 348 131 96 60 108

12 30 72 120 156 76

2.862 2.862 2.866 2.860 2.885 2.861 2.845 2.947 3.125 2.337 2.376

2.760 2.903 2.832 2.945 2.819 2.957

0.011 0.015 0.029 0.034 0.034 0.049 0.094 0.159 0.176 0.043 0.050

0.008 0.035 0.033 0.073 0.088 0.154

2.838−2.883 2.833−2.882 2.815−2.922 2.786−2.923 2.813−2.991 2.777−3.027 2.658−3.232 2.710−3.432 2.844−3.462 2.244−2.417 2.212−2.616

2.750−2.775 2.843−2.966 2.776−2.894 2.804−3.117 2.674−3.027 2.784−3.441

82 52 52

3.186 2.319 2.385

0.157 0.023 0.025

2.861−3.459 2.267−2.357 2.340−2.433

a

In Au279, Au0, central atom; Au1, Au12 along the vertices of a centered cuboctahedron core; Au2, Au42 atom shell; Au3, Au92 atom shell; and Au4, Au102 atom shell. In Au133, Au0, central atom; Au1, Au12 along the vertices of a centered icosahedron core; Au2, Au42 atom shell; and Au3, Au52 atom shell. Au(st), staple gold; S, sulfur. bN is the number of bonds; and mean is the average length of bonds; and SD is the standard deviation. cThe Au3Au(st) and Au3-S for Au133 values since it has one less shell than Au279.

important role in its stability. As noted before, the stability of nanomolecules arises from a combination of geometric, electronic and staple motif structures.8,78−81 In line with these findings, Kumara et al. have reported the probable atomic structures of three phenylethanethiolate protected F-329, F-500, and F-940 nanocrystals based on atomic pair distribution function to be TO based structures.24,25,82 Au329 has an core size of 2.2 nm, analogous to that of Au279, and it was proposed to have TO 260 or Oh core structure.82 Au∼500 and Au∼940 were found to have a TO or mDh core structure; a very close match was found between the experimental PDFs of F-500 and F-940 and simulated PDFs of TO and m-Dh models.24,25 Mass Spectrometry. Matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrum of Au279(SPh-tBu)84 nanocrystals are presented in Figure 5. MALDI-TOF-MS mass spectrum of 68.8 kDa nanocrystal under high laser fluence (Figure 5a, red spectra) shows that it has ∼54 kDa core. The absence of other peaks such as Au36 and Au133 in MALDI demonstrates the purity of the sample. The molecular formula of the titled gold nanocrystal was further confirmed to be Au279(TBBT)84 using high-resolution ESI-MS spectrum as shown in Figure 5a, blue spectrum, with a molecular weight of 68,836 Da showing multiple charge state peaks, 3+ at 22,945 Da and 4+ at 17,209 Da. While analyzing neutral molecules in ESI-MS, cesium acetate is used to facilitate the ionization of the neutral molecules by Cs+ adduct formation. Au279(TBBT)84 ionizes without Cs+ adduct formation, and such ionization without adduct formation has been reported for plasmonic nanocrystals.23 The charge state and the number of free electrons in Au279(TBBT)84 are yet to be determined. UV−vis Absorption Spectroscopy. The transition from molecular to metallic behavior in TBBT protected Au133 and F279 nanocrystals is revealed in UV−vis absorption spectra (Figure 5b). Au133 have discrete electronic transitions with optical absorption features at 430, 510, and 700 nm. The broad absorption band centered around 510 nm of Au133 is reminiscent of emergent surface plasmon resonance, whereas, F-279 nanocrystals exhibit metal-like SPR at ∼510 nm with ∼200 free electrons. A comparison between the UV−vis absorption spectra of phenylethanethiolate protected Au144(SR)60 and F-329 nanomolecules and the two TBBT

and difference in bond angle between those 6 Au red atoms and bridging sulfurs (average: 98.05° and 103.98°) compared with other monomeric staples (typically ∼90°). Along one of the {111} facets with asymmetric triangular face, one Au atom in the structure was modeled with partial occupancy of 0.3, 0.3, and 0.4 (Figure S5). The position with 0.4 occupancy alone has been used for describing the structure. Geometric and Electronic Factors Contributing to the Extraordinary Stability of F-279. In 1990s, Whetten et al. theoretically predicted that gold nanocrystal molecules could have relaxed fcc TO motifs and variants thereof as core. TO variants are formed by either addition (TO+) or removal (TO−) of layers along {111} facets of the polyhedra. TO+ was found to be one of the energetically favorable and most stable motifs, along with marks decahedral (m-Dh) and twin-faulted tTO+.6,65,66 It was shown that out of all the regular and semiregular polyhedral Archimedean structures, TO (38, 201, 586, ...) have the lowest energies, and such TO forms are close to “true Wulff construction”.61,66−70 TO+ motifs possess energies less than that of TO motifs and are comparable with that of nearly strain free m-Dh motifs.65,66 Ih motifs have higher energy than TO due to high volumetric strain. Compounds with fcc CO, and Oh motifs have higher energies as well, hence fcc TO and m-D h remain to be competitive stable structures.65,66,70 Fihey et al. have reported theoretical studies on Au249, following Wulff construction, and its optical properties exhibiting SPR.71,72 Here we present experimental evidence in the form of TO201 and TO+249 validating the theoretical predictions since the 1990s. Hence, such a relaxed geometry both internally and on surface of the TO+ 249, and the simplicity and beauty of the concentric geometric shells demonstrate that geometric factors make a major contribution toward the extraordinary stability of F-279. Au279(SPh-tBu)84 in a neutral charge state would possess 195 (279−84) free electrons. Even though we could not determine the charge state of F-279, a 3- charge state would lead to an electronic shell closing of 198 electrons.73−75 Xu et al. have reported the threshold number of Au atoms (N) where the transition from molecule-like to metal-like transition occur to be ∼263 by linear fitting the HOMO−LUMO gaps of various thiolate protected gold nanomolecules against N−1/3.76,77 The reported empirical threshold value of ∼263 is very close to the metallic F-279. It is likely that electronic factors also play an 15456


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Figure 5. (a) MALDI-MS and ESI-MS spectra of Au279(TBBT)84 protected gold nanocrystals. Red spectra correspond to the MALDI-MS of Au279 nanocrystals under high laser fluence showing 1+ and 2+ of the Au core at ∼54 kDa and ∼27 kDa, respectively. Blue spectra correspond to the ESIMS spectra of the nanocrystal showing 3+ and 4+ charge state peaks at 22,945 Da and 17,209 Da, respectively. (b) UV−vis-NIR spectrum of Au279 nanocrystals (red) compared with Au133(SR)52 (blue, dash) (SR = TBBT). were monitored using MALDI-MS. The samples were spotted using DCTB matrix85 at 20 mM concentration in toluene, and data were collected under high laser fluence (Figure 6). Step 1: Crude Synthesis. 200 mg HAuCl4·3H2O and 280 mg TOABr were dissolved in ethyl acetate (20 mL) in a 100 mL roundbottom flask under vigorous stirring for 2 h. 4-tert-Butylbenzenethiol (TBBT) (Au:Thiol = 1:2) was added to the red-colored reaction mixture and stirred for 4 h. The nearly clear polymeric (Au(I)x(SR)y) mixture was reduced with 192 mg NaBH4 (Au:NaBH4 = 1:10) dissolved in ice cold water (6 mL). Upon reduction, the reaction mixture turns black instantaneously, and the reaction was stopped after 24 h. Then the solvent was removed by rotary evaporation, and the black colored crude product was washed with methanol to remove excess thiol and other byproducts (4 times, 20 mL). The synthetic procedure is summarized in Scheme 1. MALDI-MS of the crude product is shown in the Figure 6 orange spectrum. Step 2: Thermochemical Treatment (Etching). The crude was etched with 400 μL of TBBT and 500 μL of toluene in a 10 mL roundbottom flask at 85 °C for 4−6 d. The etching reaction was monitored daily to follow the reaction progress, and the mass spectra are shown in Figure 6 (days 1−4). The etched product was rotary evaporated to remove the solvent and washed with methanol to remove the excess thiols. The etched product was washed with methanol (4 times, 20 mL) to remove excess thiol and byproducts, followed by DCM/ toluene extraction. These nanocrystals are very stable and can withstand 85 °C under ambient conditions and excess thiol for ∼10 days (Figure S7). Step 3: Isolation of Molecularly Pure Au279 Nanocrystals and Crystallization. Pink-colored Au279(TBBT)84 plasmonic gold nanocrystal was isolated by using size exclusion chromatography (SEC).84 The Bio-Rad SX1 support beads were used as a stationary phase, and THF-BHT solvent was used for loading the sample and as a mobile phase to separate the product. Typically, 20 mg of etched product was loaded on a column with 1 in. diameter and ∼20 in. long bed size. The eluted product was collected in fractions and screened using MALDITOF-MS under high laser fluence. It is very crucial to collect the data under high laser fluence and wide mass range (3−200 kDa) to reveal any higher mass polydisperse clusters present. SEC purified F-279 under high laser fluence and wide mass range is shown in Figure 6, red spectrum. Pure fractions were washed with methanol (10 mL) to remove residual amounts of BHT present in the sample and analyzed using ESI-MS. Then, molecularly pure Au279(TBBT)84 nanocrystals were crystallized by vapor diffusion of pentane into DCM solution of Au279 nanocrystals.

protected nanomolecules (Au133 and F-279) is shown in Figure S6. The SPR band of the F-329 nanocrystals is blue-shifted compared to F-279 due to the difference in ligand groups. A detailed study on the optical properties of Au279 is currently underway and is beyond the scope of this crystal structure report.

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CONCLUSIONS In summary, Au279(TBBT)84 nanocrystal is the next ultrastable size in the TBBT series of gold nanomolecules. At this size, the core structure converges from twinned icosahedral structure to a bulk fcc-like structure with truncated octahedral core. The theoretically predicted Au201 truncated octahedral core for gold clusters has been experimentally found in the Au279 structure, nested in an Au249 TO+ core. Shell growth pattern in Au279 follows fcc along {100} facets, and in {111} facets it follows fcc up to three layers, then takes a different packing due to the ligand shell. In {100} facets, the ligands are self-assembled as they would on extended Au surfaces without affecting the geometric integrity. Au279 exhibits surface plasmon resonance (SPR) at 510 nm. As this is the first crystal structure of a plasmonic Au NP, it holds the key to unlock the origin of SPR.

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EXPERIMENTAL SECTION

Materials. Hydrogen tetrachloroaurate(III) (HAuCl4.3H2O) (Alfa Aesar ACS grade), tetraoctylammonium bromide (TOABr) (Acros), sodium borohydride (NaBH4) (Acros, 99%), 4-tert-butylbenzenethiol, (TBBT) (TCI America, >97%), cesium acetate (Acros, 99%), anhydrous ethyl alcohol (Acros, 99.5%), and trans-2-[3[(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB matrix) (Fluka ≥99%) were used as received. HPLC grade solvents ethyl acetate (EtOAc), methylene chloride (DCM), tetrahydrofuran (THF), toluene, methanol, butylated hydroxytoluene stabilized tetrahydrofuran (THF-BHT), and acetonitrile were purchased from Fisher Scientific. All materials were used as received. Synthesis. The synthesis, isolation, and crystallization of 68.8 kDa Au279(TBBT)84 gold nanocrystals were carried out in three steps. The synthetic protocol is a modified version of a previous report.41 Briefly, the crude product was washed, extracted with toluene, and etched83 for 4−6 days. Titled nanocrystals were isolated using size exclusion chromatography.84 Synthesis, etching reaction, and isolation of F-279 15457


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Crystal structure data and coordinates. CCDC number is 1568278 (submitted on August 10, 2017) (CIF)

AUTHOR INFORMATION

Corresponding Author

*[email protected] ORCID

Amala Dass: 0000-0001-6942-5451 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS NSF-CHE-1255519 supported the work performed by N.S., S.T., V.G., and A.D. We dedicate this work to Prof. Royce Murray and Prof. Robert Whetten. We acknowledge Mr. Senthil Kumar Eswaramoorthy for his help with the art work.

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Figure 6. Synthesis and isolation of Au279(SR)84 nanocrystals (SR − TBBT) monitored by MALDI-MS. Top (orange) spectra correspond to the crude product, followed by mass spectra of samples during 4 days of thermochemical treatment (etch). Au279(SR)84 (bottom red spectra) was isolated by performing SEC on the 4 day etch product. Au36(SR)24 remains remarkably stable under harsh thermochemical environment. The * is polydisperse metastable clusters, and Aun(SR)m is polydisperse plasmonic clusters that are not resolved. All the spectra were collected under high laser fluence.

(1) Boisselier, E.; Astruc, D. Chem. Soc. Rev. 2009, 38, 1759. (2) Dreaden, E. C.; Alkilany, A. M.; Huang, X.; Murphy, C. J.; ElSayed, M. A. Chem. Soc. Rev. 2012, 41, 2740. (3) Mayer, K. M.; Hafner, J. H. Chem. Rev. 2011, 111, 3828. (4) Zhu, W.; Michalsky, R.; Metin, Ö .; Lv, H.; Guo, S.; Wright, C. J.; Sun, X.; Peterson, A. A.; Sun, S. J. Am. Chem. Soc. 2013, 135, 16833. (5) Abbas, M. A.; Kim, T. Y.; Lee, S. U.; Kang, Y. S.; Bang, J. H. J. Am. Chem. Soc. 2016, 138, 390. (6) Whetten, R. L.; Khoury, J. T.; Alvarez, M. M.; Murthy, S.; Vezmar, I.; Wang, Z. L.; Stephens, P. W.; Cleveland, C. L.; Luedtke, W. D.; Landman, U. Adv. Mater. 1996, 8, 428. (7) Dass, A. J. Am. Chem. Soc. 2011, 133, 19259. (8) Dass, A. Nanoscale 2012, 4, 2260. (9) Jin, R.; Zeng, C.; Zhou, M.; Chen, Y. Chem. Rev. 2016, 116, 10346. (10) Brust, M.; Walker, M.; Bethell, D.; Schiffrin, D. J.; Whyman, R. J. Chem. Soc., Chem. Commun. 1994, 0, 801. (11) Jadzinsky, P. D.; Calero, G.; Ackerson, C. J.; Bushnell, D. A.; Kornberg, R. D. Science 2007, 318, 430. (12) Häkkinen, H. Nat. Chem. 2012, 4, 443. (13) Negishi, Y.; Chaki, N. K.; Shichibu, Y.; Whetten, R. L.; Tsukuda, T. J. Am. Chem. Soc. 2007, 129, 11322. (14) Dass, A.; Jones, T. C.; Theivendran, S.; Sementa, L.; Fortunelli, A. J. Phys. Chem. C 2017, 121, 14914. (15) Heaven, M. W.; Dass, A.; White, P. S.; Holt, K. M.; Murray, R. W. J. Am. Chem. Soc. 2008, 130, 3754. (16) Zhu, M.; Aikens, C. M.; Hollander, F. J.; Schatz, G. C.; Jin, R. J. Am. Chem. Soc. 2008, 130, 5883. (17) Qian, H.; Eckenhoff, W. T.; Zhu, Y.; Pintauer, T.; Jin, R. J. Am. Chem. Soc. 2010, 132, 8280. (18) Nimmala, P. R.; Yoon, B.; Whetten, R. L.; Landman, U.; Dass, A. J. Phys. Chem. A 2013, 117, 504. (19) Negishi, Y.; Sakamoto, C.; Ohyama, T.; Tsukuda, T. J. Phys. Chem. Lett. 2012, 3, 1624. (20) Jupally, V. R.; Dass, A. Phys. Chem. Chem. Phys. 2014, 16, 10473. (21) Negishi, Y.; Nakazaki, T.; Malola, S.; Takano, S.; Niihori, Y.; Kurashige, W.; Yamazoe, S.; Tsukuda, T.; Häkkinen, H. J. Am. Chem. Soc. 2015, 137, 1206. (22) Fields-Zinna, C. A.; Sardar, R.; Beasley, C. A.; Murray, R. W. J. Am. Chem. Soc. 2009, 131, 16266. (23) Kumara, C.; Dass, A. Anal. Chem. 2014, 86, 4227. (24) Kumara, C.; Zuo, X.; Ilavsky, J.; Chapman, K. W.; Cullen, D. A.; Dass, A. J. Am. Chem. Soc. 2014, 136, 7410. (25) Kumara, C.; Zuo, X.; Cullen, D. A.; Dass, A. ACS Nano 2014, 8, 6431. (26) Chaki, N. K.; Negishi, Y.; Tsunoyama, H.; Shichibu, Y.; Tsukuda, T. J. Am. Chem. Soc. 2008, 130, 8608.

Scheme 1

Instrumentation. MALDI-TOF mass spectra used 20 mM DCTB matrix in toluene with a Voyager DE PRO mass spectrometer from applied Biosystems. ESI-MS was collected from Waters Synapt HDMS with THF as the solvent, and cesium acetate was added to facilitate ionization of neutral molecules. Optical UV−Vis−NIR absorption data were collected using a Shimadzu UV-1601 spectrophotometer with toluene as the solvent. Crystal structure. Crystal data for C840H1092Au279S84; Mr = 68836.87; Monoclinic; space group P21/n; a = 35.924(5) Å; b = 95.717(12) Å; c = 36.659(5) Å; α = 90°; β = 94.532(8)°; γ = 90°; V = 125659(28) Å3; Z = 4; T = 120(2) K; λ(Cu−Kα) = 1.54184 Å; μ(Cu−Kα) = 60.971 mm−1; dcalc = 3.637g·cm−3; 320841 reflections collected; 95334 unique (Rint = 0.0901); giving R1 = 0.1372, wR2 = 0.3456 for 44,100 data with [I > 2σ(I)] and R1 = 0.2513, wR2 = 0.3968 for all 95,334 data. Residual electron density (e−·Å−3) max/min: 12.087/−9.824. An arbitrary sphere of data was collected on a black tablet-like crystal, having approximate dimensions of 0.06 × 0.05 × 0.01 mm, with a Bruker APEX-II diffractometer using a combination of ω- and φ-scans of 0.5°.86 Data were corrected for absorption and polarization effects and analyzed for space group determination.87 The structure was solved by direct methods and expanded routinely.88 The model was refined by full-matrix least-squares analysis of F2 against all reflections.89

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REFERENCES

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.7b08651. Detailed figures illustrating complementary core−shell structure, alternate core view, point group, partial occupancy atom in the structure model (PDF) 15458


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Journal of the American Chemical Society (27) Nimmala, P. R.; Knoppe, S.; Jupally, V. R.; Delcamp, J. H.; Aikens, C. M.; Dass, A. J. Phys. Chem. B 2014, 118, 14157. (28) Dass, A.; Jones, T.; Rambukwella, M.; Crasto, D.; Gagnon, K. J.; Sementa, L.; De Vetta, M.; Baseggio, O.; Aprà, E.; Stener, M.; Fortunelli, A. J. Phys. Chem. C 2016, 120, 6256. (29) Pei, Y.; Zeng, X. C. Nanoscale 2012, 4, 4054. (30) Chen, S.; Ingram, R. S.; Hostetler, M. J.; Pietron, J. J.; Murray, R. W.; Schaaff, T. G.; Khoury, J. T.; Alvarez, M. M.; Whetten, R. L. Science 1998, 280, 2098. (31) Antonello, S.; Holm, A. H.; Instuli, E.; Maran, F. J. Am. Chem. Soc. 2007, 129, 9836. (32) Murray, R. W. Chem. Rev. 2008, 108, 2688. (33) Jupally, V. R.; Thrasher, J. G.; Dass, A. Analyst 2014, 139, 1826. (34) Quinn, B. M.; Liljeroth, P.; Ruiz, V.; Laaksonen, T.; Kontturi, K. J. Am. Chem. Soc. 2003, 125, 6644. (35) Ingram, R. S.; Hostetler, M. J.; Murray, R. W.; Schaaff, T. G.; Khoury, J. T.; Whetten, R. L.; Bigioni, T. P.; Guthrie, D. K.; First, P. N. J. Am. Chem. Soc. 1997, 119, 9279. (36) Link, S.; El-Sayed, M. A. Annu. Rev. Phys. Chem. 2003, 54, 331. (37) Ramakrishna, G.; Varnavski, O.; Kim, J.; Lee, D.; Goodson, T. J. Am. Chem. Soc. 2008, 130, 5032. (38) Zhou, M.; Zeng, C.; Chen, Y.; Zhao, S.; Sfeir, M. Y.; Zhu, M.; Jin, R. Nat. Commun. 2016, 7, 13240. (39) Miller, S. A.; Womick, J. M.; Parker, J. F.; Murray, R. W.; Moran, A. M. J. Phys. Chem. C 2009, 113, 9440. (40) Varnavski, O.; Ramakrishna, G.; Kim, J.; Lee, D.; Goodson, T. J. Am. Chem. Soc. 2010, 132, 16. (41) Dass, A.; Theivendran, S.; Nimmala, P. R.; Kumara, C.; Jupally, V. R.; Fortunelli, A.; Sementa, L.; Barcaro, G.; Zuo, X.; Noll, B. C. J. Am. Chem. Soc. 2015, 137, 4610. (42) Antonello, S.; Dainese, T.; Pan, F.; Rissanen, K.; Maran, F. J. Am. Chem. Soc. 2017, 139, 4168. (43) Zeng, C.; Chen, Y.; Iida, K.; Nobusada, K.; Kirschbaum, K.; Lambright, K. J.; Jin, R. J. Am. Chem. Soc. 2016, 138, 3950. (44) Zeng, C.; Liu, C.; Chen, Y.; Rosi, N. L.; Jin, R. J. Am. Chem. Soc. 2016, 138, 8710. (45) Zeng, C.; Chen, Y.; Kirschbaum, K.; Appavoo, K.; Sfeir, M. Y.; Jin, R. Sci. Adv. 2015, 1, e1500045. (46) Liao, L.; Chen, J.; Wang, C.; Zhuang, S.; Yan, N.; Yao, C.; Xia, N.; Li, L.; Bao, X.; Wu, Z. Chem. Commun. 2016, 52, 12036. (47) Theivendran, S.; Dass, A. Langmuir 2017, 33, 7446. (48) Nimmala, P. R.; Theivendran, S.; Barcaro, G.; Sementa, L.; Kumara, C.; Jupally, V. R.; Apra, E.; Stener, M.; Fortunelli, A.; Dass, A. J. Phys. Chem. Lett. 2015, 6, 2134. (49) Liao, L.; Yao, C.; Wang, C.; Tian, S.; Chen, J.; Li, M.-B.; Xia, N.; Yan, N.; Wu, Z. Anal. Chem. 2016, 88, 11297. (50) Chen, Y.; Zeng, C.; Liu, C.; Kirschbaum, K.; Gayathri, C.; Gil, R. R.; Rosi, N. L.; Jin, R. J. Am. Chem. Soc. 2015, 137, 10076. (51) Zeng, C.; Chen, Y.; Kirschbaum, K.; Lambright, K. J.; Jin, R. Science 2016, 354, 1580. (52) Higaki, T.; Liu, C.; Zhou, M.; Luo, T.-Y.; Rosi, N. L.; Jin, R. J. Am. Chem. Soc. 2017, 139, 9994. (53) Vergara, S. L. D. A.; Martynowycz, M. W.; Santiago, U.; Plascencia-Villa, G.; Weiss, S. C.; de la Cruz, M. J.; Black, D. M.; Alvarez, M. M.; Lopez-Lozano, X.; Barnes, C. O.; Lin, G.; Weissker, H.; Whetten, R. L.; Gonen, T.; Calero, G. as published on arXiv:1706.07902 preprint service 2017. (54) Tran, N. T.; Powell, D. R.; Dahl, L. F. Angew. Chem., Int. Ed. 2000, 39, 4121. (55) Mednikov, E. G.; Jewell, M. C.; Dahl, L. F. J. Am. Chem. Soc. 2007, 129, 11619. (56) Chen, Z.-Y.; Tam, D. Y. S.; Mak, T. C. W. Nanoscale 2017, 9, 8930. (57) Yang, H.; Wang, Y.; Chen, X.; Zhao, X.; Gu, L.; Huang, H.; Yan, J.; Xu, C.; Li, G.; Wu, J.; Edwards, A. J.; Dittrich, B.; Tang, Z.; Wang, D.; Lehtovaara, L.; Häkkinen, H.; Zheng, N. Nat. Commun. 2016, 7, 12809. (58) Faraday, M. Philos. Trans. R. Soc. London 1857, 147, 145. (59) Teo, B. K.; Sloane, N. J. A. Inorg. Chem. 1985, 24, 4545.

(60) Hermann, K. Bulk Crystals: Three-Dimensional Lattices. In Crystallography and Surface Structure: An Introduction for Surface Scientists and Nanoscientists; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2016; pp 7−89. (61) Baletto, F.; Ferrando, R. Rev. Mod. Phys. 2005, 77, 371. (62) Alvarez, S. Dalton Trans. 2005, 2209. (63) Volkov, V. V.; Van Tendeloo, G.; Tsirkov, G. A.; Cherkashina, N. V.; Vargaftik, M. N.; Moiseev, I. I.; Novotortsev, V. M.; Kvit, A. V.; Chuvilin, A. L. J. Cryst. Growth 1996, 163, 377. (64) K.H, K. Mackay, Anti-Mackay, Double-Mackay, Pseudo-Mackay, and Related Icosahedral Shell Clusters. In Science of Crystal Structures;Hargittai, I., Hargittai, B., Ed.; Springer: Cham, 2015. (65) Cleveland, C. L.; Landman, U.; Schaaff, T. G.; Shafigullin, M. N.; Stephens, P. W.; Whetten, R. L. Phys. Rev. Lett. 1997, 79, 1873. (66) Cleveland, C. L.; Landman, U.; Shafigullin, M. N.; Stephens, P. W.; Whetten, R. L. Z. Phys. D: At., Mol. Clusters 1997, 40, 503. (67) Cleveland, C. L.; Landman, U. J. Chem. Phys. 1991, 94, 7376. (68) Barnard, A. S.; Curtiss, L. A. ChemPhysChem 2006, 7, 1544− 1553. (69) Wulff, G. Z. Kristallogr. - Cryst. Mater. 1901, 34, 449. (70) Li, H.; Li, L.; Pedersen, A.; Gao, Y.; Khetrapal, N.; Jónsson, H.; Zeng, X. C. Nano Lett. 2015, 15, 682. (71) Fihey, A.; Kloss, B.; Perrier, A.; Maurel, F. J. Phys. Chem. A 2014, 118, 4695. (72) Fihey, A.; Maurel, F.; Perrier, A. J. Phys. Chem. C 2015, 119, 9995. (73) de Heer, W. A. Rev. Mod. Phys. 1993, 65, 611. (74) Li, X.; Wu, H.; Wang, X.-B.; Wang, L.-S. Phys. Rev. Lett. 1998, 81, 1909−1912. (75) Walter, M.; Akola, J.; Lopez-Acevedo, O.; Jadzinsky, P. D.; Calero, G.; Ackerson, C. J.; Whetten, R. L.; Groenbeck, H.; Hakkinen, H.; Grönbeck, H. Proc. Natl. Acad. Sci. U. S. A. 2008, 105, 9157. (76) Xu, W. W.; Gao, Y. J. Phys. Chem. C 2015, 119, 14224. (77) Jin, R. Nanoscale 2015, 7, 1549. (78) Xu, W. W.; Zhu, B.; Zeng, X. C.; Gao, Y. Nat. Commun. 2016, 7, 13574. (79) Jiang, D.-e.; Tiago, M. L.; Luo, W.; Dai, S. J. Am. Chem. Soc. 2008, 130, 2777. (80) Jiang, D.-e. Chem. - Eur. J. 2011, 17, 12289. (81) Desireddy, A.; Kumar, S.; Guo, J.; Bolan, M. D.; Griffith, W. P.; Bigioni, T. P. Nanoscale 2013, 5, 2036. (82) Kumara, C.; Zuo, X.; Ilavsky, J.; Cullen, D.; Dass, A. J. Phys. Chem. C 2015, 119, 11260. (83) Schaaff, T. G.; Whetten, R. L. J. Phys. Chem. B 1999, 103, 9394. (84) Knoppe, S.; Boudon, J.; Dolamic, I.; Dass, A.; Bürgi, T. Anal. Chem. 2011, 83, 5056. (85) Dass, A.; Stevenson, A.; Dubay, G. R.; Tracy, J. B.; Murray, R. W. J. Am. Chem. Soc. 2008, 130, 5940. (86) APEX-3; Bruker AXS: Madison, WI, 2016. (87) Krause, L.; Herbst-Irmer, R.; Sheldrick, G. M.; Stalke, D. J. Appl. Crystallogr. 2015, 48, 3. (88) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Adv. 2015, 71, 3. (89) Sheldrick, G. M. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3.

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Crystal Structure of Faradaurate-279: Au279(SPh ... - ACS Publications

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