Assembling Atomically Precise Noble Metal Nanoclusters Using Supramolecular Interactions

Abstract

Supramolecular chemistry (SC) of noble metal nanoclusters (NMNCs) is one of the fascinating areas of contemporary materials science. It is principally concerned with the noncovalent interactions between NMNCs, as well as between NMNCs and molecules or nanoparticles. This review focuses on recent advances in the supramolecular assembly of NMNCs and applications of the resulting structures. We have divided the topics into four distinct subgroups: (i) SC of NMNCs in gaseous and solution phases, (ii) supramolecular interactions of NMNCs in crystal lattices, (iii) supramolecular assemblies of NMNCs with nanoparticles and NMNCs, and (iv) SC of NMNCs with other molecules. The last explores their interactions with fullerenes, cyclodextrins, cucurbiturils, crown ethers, and more. After discussing these topics concisely, various emerging properties of the assembled systems in terms of their mechanical, optical, magnetic, charge-transfer, etc. properties and applications are presented. SC is seen to provide a crucial role to induce new physical and chemical properties in such hybrid nanomaterials. Finally, we highlight the scope for expansion and future research in the area. This review would be useful to those working on functional nanostructures in general and NMNCs in particular.

Figure 1

Various kinds of supramolecular assemblies of atomically precise NCs. Individual structures have been gathered from refs (20, 38, 43, 44, 46, 48, 53, 64, 65, 67, 69, 81, 82, 86), and. At the center, an isolated ligand-protected cluster has been redrawn from ref (47).

Figure 2

(A) (a) Formation of [Au₂₅Ag₂₅(PET)₁₈(DMBT)₁₈]^2– heterodimer via intercluster reaction between [Ag₂₅(DMBT)₁₈]^1– and [Au₂₅(PET)₁₈]^1–. (b) Experimental and calculated isotopic patterns for the dimer confirming the charge state of 2^–. (c) DFT optimized structure of the adduct [Au₂₅Ag₂₅(PET)₁₈(DMBT)₁₈]^2–. Color codes: white, H; yellow, S; red, Au; green, Ag; cyan, C. (Reproduced from ref (38). Copyright 2016 Nature Publishing Group.) (B) (a and b) Isotopic patterns and mobility distributions of [Au₂₅(PET)₁₈]^1– and [Au₅₀(PET)₃₆]^2– at the collision energies (CEs) 30 and 5 eV, respectively. With the increase of CE, the dimer is converted to a monomer. (c) DFT optimized structure and Borromean ring model of [Au₅₀(PET)₃₆]^2–. Color codes: pale red, S; orange, Au. (Adopted from ref (39). Copyright 2016 Royal Society of Chemistry.) (C) (a) Mobility distributions of [Ag₂₉(S₂R)₁₂Na]^2– and [Ag₂₉(S₂R)₁₂Na]₂^4– with different drifts (S₂R = BDT: 1,3-benzenedithiol). (b) DFT optimized structure of [Ag₂₉(S₂R)₁₂Na]₂^4–. Color codes: yellow, S; blue and red, Ag; purple, Na; white, H; gray, carbon. (Adopted from ref (43). Copyright 2016 Royal Society of Chemistry.)

Figure 3

(A) Schematic representation of the luminescent enhancement of [Ag₂₉(S₂R)₁₂(TPP)₄] in solution by the dissociation–aggregation process (S₂R = BDT). (B) (i) π···π interaction between S₂R ligands and (ii) π···H–C interaction between S₂R and TPP ligands, respectively. (Reproduced from ref (44). Copyright 2018 Royal Society of Chemistry.) (C) Emission and excitation spectra of NCs with different secondary ligands; each set is presented using the same color code. The DFT optimized structure of [Ag₂₉(S₂R)₁₂] is presented in the inset. About 30 times enhancement in PL intensity related to its parent NMNC, [Ag₂₉(S₂R)₁₂(TPP)₄], was confirmed when TPP was replaced with DPPP. (Reproduced from ref (46). Copyright 2018 Royal Society of Chemistry.)

Figure 4

(A) Packing of [Au₂₄₆(p-MBT)₈₀] in the unit cell. Views from the (a) z-direction, (b) y-direction, (c) and x-direction. Color codes: [Au₂₄₆(p-MBT)₈₀] with different chirality, gold, blue, and magenta; sulfur, yellow; carbon, gray. (d–f) Arrangement of ligands of [Au₂₄₆(p-MBT)₈₀] along the z-, y-, and x-directions. Color codes: ligands positioned at the middle of [Au₂₄₆(p-MBT)₈₀], gray, red, blue, and green; ligands positioned at the extremes, green, blue, and red. (B) Intercluster self-assembly generated by the ligands. (a and b) Coordination geometry of [Au₂₄₆(p-MBT)₈₀] in the unit cell: side view (a) and top view (b). (c) Interactions among the intercluster ligands. (d) Side-by-side assembly of the ligands in [Au₂₄₆(p-MBT)₈₀] with the same chirality. (e) Point-to-point assembling of the ligands in [Au₂₄₆(p-MBT)₈₀] with opposite chirality. (f) Schematic representation of the directional packing of [Au₂₄₆(p-MBT)₈₀]. (C) Various π···H–C interactions between the ligands of NMNC: (a) rotational and (b) parallel patterns. (Reproduced from ref (47). Copyright 2016 American Association for the Advancement of Science.)

Figure 5

(A) Cubic unit cell and (B) trigonal unit cell of Ag₂₉ NMNC. (C) Emission spectra of the cubic and trigonal crystals of the NMNC. (Adopted from ref (53). Copyright 2018 Royal Society of Chemistry.) (D) Structure of Ag₂₉ NMNC. (E) Crystal structure of [Ag₂₉Cs₃(S₂R)₁₂(DMF)_m] (m = 5, 6). (Adopted from ref (58). Copyright 2019 American Chemical Society.)

Figure 6

(A) (a) Crystal structures of the [Au₁₀₃S₂(S-Nap)₄₁] NMNC, Au₇₉ (middle), and ligands (right). Color codes: magenta and blue, Au; yellow, S; white, H. (b) Intracluster interactions via ligands. (c) T-shaped arrangement adopted a ‘‘herringbone pattern” via π···H–C. (B) (a) Intercluster interactions (π···H–C) in the crystal lattice of Au₁₀₃ NMNC. (b) Intercluster and intracluster interactions resulted in the “herringbone pattern”. (Adopted from ref (54). Copyright 2017 American Chemical Society.)

Figure 7

(A) Schematic representation of the interactions between [Ag₄₄(SR)₃₀] and Te NWs. (B) Total structure of [Ag₄₄(p-MBA)₃₀]. (C) Formation of the crossed-bilayer assembly (CBA) of Ag44@Te NWs shown via TEM images. (D) H-bonding between the carboxylic group of the ligand of adjoining. The adjoining NCs’ network via H-bonding with L₂ (i) and L₃ (ii) fashion. (E) (i) Schematic representation of the CBA. (ii) Zoom in view of the area shown in (i). Further zoom in view is presented in (iii). Different NCs are labeled as C₁, C₂, and C₃. (Reproduced from refs (28, 64), and (68). Copyright 2019 American Chemical Society, 2016 and 2017 Wiley.)

Figure 8

(A) (a) ESI-MS of [Ag₂₉(S₂R)₁₂(C₆₀)_n]^3– (n = 1–4) adducts. (b) Theoretical and experimental isotopic patterns of [Ag₂₉(S₂R)₁₂(C₆₀)₁]^3–. (c) DFT optimized structure of [Ag₂₉(S₂R)₁₂(C₆₀)₄]^3–. (B) Strong noncovalent interactions between the NMNC and C₆₀. (Reproduced from ref (69). Copyright 2018 American Chemical Society.) (C) Fullerene (C₆₀) induced aggregation of [Ag₂₅(SR)₁₈]⁻. (Adopted from the ref (70). Copyright 2020 American Chemical Society.) (D) Assembly of [Au₈(TPP)₈(C₆₀)₂] along the (001) plane. (Reproduced from the ref (71). Copyright 2008 Wiley.)

Figure 9

(A) ESI-MS of the [Au₂₅SBB₁₈∩CD_n] (n = 1–4) adducts. (B) Schematic presentation of the [Au₂₅(SBB)₁₈∩(β-CD)_n] (n = 1–4) adducts. (Adopted from ref (72). Copyright 2014 American Chemical Society.) (C) Schematic presentation of (a) [Ag₂₉(S₂R)₁₂] where S₂R is BDT and (b) β-CDs. (D) Simple presentation of the isomers of [Ag₂₉(S₂R)₁₂∩(CD)_n] (n = 2 to 3). (Reproduced from ref (81). Copyright 2018 American Chemical Society). (E) Supramolecular interactions of CB[8] with AuNCs resulted in enhancement in luminescence. (Adopted from ref (82). Copyright 2020 Royal Society of Chemistry.) (F) (i) DFT optimized structure of [Ag₂₉(LA)₁₂CB[7]₁]. (ii) Highly luminescent [Ag₂₉(LA)₁₂CB[7]] complexes in water. (Reproduced from ref (85). Copyright 2020 American Chemical Society.)

Figure 10

(A) Crystal structure of [Ag₂₉(S₂R)₁₂(TPP)₄]^3– with dibenzo-18-crown-6. (B) Supramolecular interaction between one of the DB₁₈C₆Na⁺ and S₂R and TPP of the NMNC. (C) Zoomed in view of the three DB₁₈C₆Na⁺ molecules connected to the NMNC. Color codes: Ag, gray; S, yellow; P, orange; O, red; C of TPP and S₂R, green; H of TPP and S₂R, white; H and C of DB₁₈C₆, light blue; Na, pink. Color codes in part C: C and H of the three DB₁₈C₆Na⁺ molecules, light blue, dark blue, and purple, respectively. (D) Formation of coassembly of [Ag₂₉(S₂R)₁₂(TPP)₄]^3– with dibenzo-18-crown-6 via supramolecular interactions. (Adopted from ref (86). Copyright 2019 American Chemical Society.)

Figure 11

(A) Synthesis of [Ag₂₉(LA-P₅)₁₂(TPP)₂] via two methods: (i) direct synthesis and (ii) ligand exchange. (B) Schematic representation of host–guest interaction between [Ag₂₉(LA-P₅)₁₂(TPP)₂] and CTAB leading to self-assembly and luminescence enhancement. (Reproduced from ref (87). Copyright 2019 Wiley.)

Figure 12

(A) Study of the mechanical properties of single crystals of NMNCs such as dithiol-protected Ag₂₉ polymorphs (C and T), monothiol-protected Ag₄₆, and its cocrystal with Ag₄₀. (Reproduced from ref (90). Copyright 2020 American Chemical Society.) (B) γ-CD-MOF induced water solubility of [Au₄₀(S-Adm)₂₂] NMNCs. This water-soluble hybrid component activated gold NCs for the horseradish peroxidase (HRP)-mimicking catalysis. (Adopted from ref (98). Copyright 2020 American Chemical Society.)