Correction: Secondary ligand-induced orthogonal self-assembly of silver nanoclusters into superstructures with enhanced NIR emission.

Correction for 'Secondary ligand-induced orthogonal self-assembly of silver nanoclusters into superstructures with enhanced NIR emission' by Korath Shivan Sugi, et al., Nanoscale, 2023, https://doi.org/10.1039/d3nr02561f.

Secondary ligand-induced orthogonal self-assembly of silver nanoclusters into superstructures with enhanced NIR emission.

Orthogonal self-assembly is one of the crucial strategies for forming complex and hierarchical structures in biological systems. However, creating such ordered complex structures using synthetic nanoparticles is a challenging task and requires a high degree of control over structure and multiple non-covalent interactions. In this context, nanoarchitectonics serves as an emerging tool to fabricate complex functional materials. Here, we present a secondary ligand-induced orthogonal self-assembly of atomically precise silver nanoclusters into complex superstructures. Specifically, we use Ag14NCs protected with naphthalene thiol and 1,6-bis(diphenylphosphino)hexane ligands. Controlled addition of 1,6-bis(diphenylphosphino)hexane, the secondary ligand resulted in a self-assembled supracolloidal structure including helical fibers, spheres, and nanosheets. The self-assembly process is tunable by controlling the molar ratio of the ligand. The resulting superstructures exhibit enhanced NIR emission due to restricted intramolecular motion. This demonstrates that by tuning supramolecular interactions, hierarchical nanostructures with desired properties similar to biomolecules can be obtained from atomically precise building blocks.

Carborane-thiol protected copper nanoclusters: stimuli-responsive materials with tunable phosphorescence.

Atomically precise nanomaterials with tunable solid-state luminescence attract global interest. In this work, we present a new class of thermally stable isostructural tetranuclear copper nanoclusters (NCs), shortly Cu4@oCBT, Cu4@mCBT and Cu4@ICBT, protected by nearly isomeric carborane thiols: ortho-carborane-9-thiol, meta-carborane-9-thiol and ortho-carborane 12-iodo 9-thiol, respectively. They have a square planar Cu4 core and a butterfly-shaped Cu4S4 staple, which is appended with four respective carboranes. For Cu4@ICBT, strain generated by the bulky iodine substituents on the carboranes makes the Cu4S4 staple flatter in comparison to other clusters. High-resolution electrospray ionization mass spectrometry (HR ESI-MS) and collision energy-dependent fragmentation, along with other spectroscopic and microscopic studies, confirm their molecular structure. Although none of these clusters show any visible luminescence in solution, bright µs-long phosphorescence is observed in their crystalline forms. The Cu4@oCBT and Cu4@mCBT NCs are green emitting with quantum yields (Φ) of 81 and 59%, respectively, whereas Cu4@ICBT is orange emitting with a Φ of 18%. Density functional theory (DFT) calculations reveal the nature of their respective electronic transitions. The green luminescence of Cu4@oCBT and Cu4@mCBT clusters gets shifted to yellow after mechanical grinding, but it is regenerated after exposure to solvent vapour, whereas the orange emission of Cu4@ICBT is not affected by mechanical grinding. Structurally flattened Cu4@ICBT didn't show mechanoresponsive luminescence in contrast to other clusters, having bent Cu4S4 structures. Cu4@oCBT and Cu4@mCBT are thermally stable up to 400 °C. Cu4@oCBT retained green emission even upon heating to 200 °C under ambient conditions, while Cu4@mCBT changed from green to yellow in the same window. This is the first report on structurally flexible carborane thiol appended Cu4 NCs having stimuli-responsive tunable solid-state phosphorescence.

Cocrystals of Atomically Precise Noble Metal Nanoclusters.

Cocrystallization is a phenomenon involving the assembly of two or more different chemical entities in a lattice, occurring typically through supramolecular interactions. In this concept, recent advancements in the cocrystallization of atomically precise noble metal clusters and their potential future directions are presented. Different strategies to create coassemblies of thiolate-protected noble metal nanoclusters are presented first. An approach is the simultaneous synthesis, and cocrystallization of two clusters having similar structures. A unique pair of clusters found recently, namely Ag40 and Ag46 with same core but different shell are taken to illustrate this. In another category, the case of the same core is presented, namely Ag116 with different shells, as in a mixture of Ag210 and Ag211 . Next, an intercluster reaction is presented to create cocrystals through selective crystallization of the reaction products. The coexistence of competing effects, magic sizes, and magic electron shells in a coassembly of alloy nanoclusters is discussed next. Finally, an assembly strategy for nanoclusters using electrostatic interactions is described. This concept is concluded with a future perspective on the emerging possibilities of such solids. Advancements in this field will certainly help the development of novel materials with exciting properties.

Dual emitting Ag35 nanocluster protected by 2-pyrene imine thiol.

In this communication, we present the synthesis of 2-pyrene imine thiol (2-PIT)-protected Ag35 nanoclusters using a ligand exchange-induced structural transformation reaction. The formation of the nanocluster and its composition were confirmed through several spectroscopic and electron microscopic studies. The UV-vis absorption spectrum showed a set of characteristic features of the nanocluster. This nanocluster showed blue emission under UV light due to pyrene to metal core charge-transfer, and NIR emission due to charge-transfer within the metal core. This is the first report on dual emitting pyrene protected atomically precise silver nanoclusters.

Interparticle Reactions between Silver Nanoclusters Leading to Product Cocrystals by Selective Cocrystallization.

We present an example of an interparticle reaction between atomically precise nanoclusters (NCs) of the same metal, resulting in entirely different clusters. In detail, the clusters [Ag12(TBT)8(TFA)5(CH3CN)]+ (TBT = tert-butylthiolate, TFA = trifluoroacetate, CH3CN = acetonitrile) and [Ag18(TPP)10H16]2+ (TPP = triphenylphosphine) abbreviated as Ag12 and Ag18, respectively, react leading to [Ag16(TBT)8(TFA)7(CH3CN)3Cl]+ and [Ag17(TBT)8(TFA)7(CH3CN)3Cl]+, abbreviated as Ag16 and Ag17, respectively. The two product NCs crystallize together as both possess the same metal chalcogenolate shell, composed of Ag16S8, making them indistinguishable. The occupancies of Ag16 and Ag17 are 66.66 and 33.33%, respectively, in a single crystal. Electrospray ionization mass spectrometry (ESI MS) of the reaction product and a dissolved crystal show the population of Ag16 and Ag17 NCs to be in a 1:1 and 2:1 ratio, respectively. This suggests selective crystallization in the cocrystal. Time-dependent ESI MS was employed to understand the formation of product clusters by monitoring the reaction intermediates formed in the course of the reaction. We present an unprecedented growth mechanism for the formation of silver NCs mediated by silver thiolate intermediates.

Confining an Ag10 Core in an Ag12 Shell: A Four-Electron Superatom with Enhanced Photoluminescence upon Crystallization.

We introduce a cluster coprotected by thiol and diphosphine ligands, [Ag22(dppe)4(2,5-DMBT)12Cl4]2+ (dppe = 1,2-bis(diphenylphosphino)ethane; 2,5-DMBT= 2,5-dimethylbenzenethiol), which has an Ag10 core encapsulated by an Ag12(dppe)4(2,5-DMBT)12Cl4 shell. The Ag10 core comprises two Ag5 distorted trigonal bipyramidal units and is uncommon in Au and Ag nanoclusters. The electrospray ionization mass spectrum reveals that the cluster is divalent and contains four free electrons. An uncommon crystallization-induced enhancement of emission is observed in the cluster. The emission is weak in the solution and amorphous states. However, it is enhanced 12 times in the crystalline state compared to the amorphous state. A detailed investigation of the crystal structure suggests that well-arranged C-H···π and π···π interactions between the ligands are the major factors for this enhanced emission. Further, in-depth structural elucidation and density functional theory calculations suggest that the cluster is a superatom with four magic electrons.

Phase controlled colour tuning of samarium and europium complexes and excellent photostability of their PVA encapsulated materials. Structural elucidation, photophysical parameters and the energy transfer mechanism in the Eu(3+) complex by Sparkle/PM3 calculations.

Luminescent [Sm(acac)3(pyz)2] (1) and [Eu(acac)3(pyz)2] (2) complexes (acac is the anion of acetylacetone and pyz is pyrazine) have been synthesized and thoroughly characterized by microanalyses, TGA, DTA, IR, ESI-MS(+) and NMR spectroscopy. The photophysical properties of these complexes have been investigated. The Sparkle/PM3 model was utilized for predicting the ground-state geometry of (2). The Judd-Ofelt intensity parameters, radiative parameters, intramolecular energy transfer rates and quantum efficiency are calculated and discussed. The intramolecular energy transfer rates predict that the major energy transfer (96%) is from the ligand triplet state to the levels (5)D1 (74.53%) and (5)D0 (21.87%) of the Eu(3+) ion, in the complex. Complexes (1) and (2) were analysed for colour tuning properties and these show varying colours upon changing phases. This property would possibly allow the use of these complexes as 'colour indicators'. The photoluminescence and photostability of the thin hybrid films of both complexes (1) and (2) in polyvinyl alcohol (PVA) are investigated and discussed. The hybrid films of (1) and (2) are quite robust due to their higher photostability. An important feature of complex (2) is that the excitation window extends close to the visible range (393 nm). The lasing property of the Eu(3+) complex in various phases is also presented.