Facile Synthesis of High Nuclearity Silver–Ferrocenyldiselenolate Clusters

New protective ligands for atomically precise silver nanoclusters

Atomically precise silver nanoclusters (NCs) have emerged as a hot topic attracting immense research interest. Protecting ligands are needed for direct capping on cluster surfaces in order to prevent aggregation and to stabilize NCs. It has been demonstrated that protective ligands are critical to determining the sizes, structures and properties of silver NCs. The past decades have witnessed conventionally used organic ligands (thiolates/selenols, phosphines and alkynyls) and inorganic ligands (chalcogens and halogens) being extensively used to passivate NC surfaces. However, only in the most recent years have new-type protecting ligands beyond the conventional ones begun to be introduced in the protecting sphere of new functional silver NCs. The present Frontier article covers the most recent examples of some new protective agents for well-defined silver NCs. We describe four classes of novel silver NCs stabilized by newly-developed surface ligands, namely, nitrogen-donor organic ligands, oxygen-donor inorganic ligands, metalloligands and macrocyclic hosts, paying attention to the synthesis, structures and properties of these silver NCs. This Frontier article will hopefully attract more cluster scientists to explore more freshly ligated atomically precise silver NCs with novel structures and properties in the years ahead. The literature survey in this review is based on publications up to February 2020. Some suggestions for future directions in this field are also given.

Metal Nanoclusters Stabilized by Selenol Ligands

The past decades have witnessed great advances in controllable synthesis, structure determination, and property investigation of metal nanoclusters. Selenolated nanoclusters, a special branch in the nanocluster family, have attracted great interest in these years. The electronegativity and atomic radius of selenium is different from sulfur, and thus the selenolated nanoclusters are anticipated to display different electronic/geometric structures and distinct chemical/physical properties relative to their thiolated analogues. This review covers the syntheses, structures, and properties of selenolated nanoclusters (including Au, Ag, Cu, and alloy nanoclusters). Ligand effects (between SeR and SR) on nanocluster properties, including optical absorption, stability, and electrochemical properties, are disclosed as well. At the end of the review, a scope for improvements and future perspectives of selenolated nanoclusters is highlighted. The review hopefully opens up new horizons for cluster scientists to synthesize more selenolated nanoclusters with novel structures and properties. This review is based on publications available up to May 2019.

Recent advances in the self-assembly of polynuclear metal–selenium and –tellurium compounds from 14–16 reagents

The use of reagents containing bonds between group 14 elements and Se or Te for the self-assembly of polynuclear metal–chalcogen compounds is covered. Background material is briefly reviewed and examples from the literature are highlighted from the period 2007–2017. Emphasis is placed on the different classes of 14–16 precursors and their application in the targeted synthesis of metal–chalcogen compounds. The unique properties arising from the combination of specific 14–16 precursors, metal atoms, and ancillary ligands are also described. Selected examples are chosen to underline the progress in (i) controlled synthesis of heterometallic (ternary) chalcogen clusters, (ii) chalcogen clusters with organic functionalized surfaces, and (iii) crystalline open-framework metal chalcogenides.

New polydentate trimethylsilyl chalcogenide reagents for the assembly of polyferrocenyl architectures

A series of polychalcogenotrimethylsilane complexes Ar(CH2ESiMe3)n, (Ar = aryl; E = S, Se; n = 2, 3, and 4) can be prepared from the corresponding polyorganobromide and M[ESiMe3] (M = Na, Li). These represent the first examples of the incorporation of such a large number of reactive -ESiMe3 moieties onto an organic molecular framework. They are shown to be convenient reagents for the preparation of the polyferrocenylseleno- and thioesters from ferrocenoyl chloride. The synthesis, structures, and spectroscopic properties of the new silyl chalcogen complexes 1,4-(Me3SiECH2)2(C6Me4) (E = S, 1; E = Se, 2), 1,3,5-(Me3SiECH2)3(C6Me3) (E = S, 3; E = Se, 4) and 1,2,4,5-(Me3SiECH2)4(C6H2) (E = S, 5; E = Se, 6) and the polyferrocenyl chalcogenoesters [1,4-{FcC(O)ECH2}2(C6Me4)] (E = S, 7; E = Se, 8), [1,3,5-{FcC(O)ECH2}3(C6Me3)] (E = S, 9; E = Se, 10) and [1,2,4,5-{FcC(O)ECH2}4(C6H2)] (E = S, 11 illustrated; E = Se, 12) are reported. The new polysilylated reagents and polyferrocenyl chalcogenoesters have been characterized by multinuclear NMR spectroscopy ((1)H, (13)C, (77)Se), electrospray ionization mass spectrometry and, for complexes 1, 2, 3, 4, 7, 8, and 11, single-crystal X-ray diffraction. The cyclic voltammograms of complexes 7-11 are presented.

Ferrocenyl functionalized silver-chalcogenide nanoclusters

New (chalcogenoethyl)ferrocenylcarboxalate functionalized silver chalcogenide nanoclusters were synthesized using a combination of silylated chalcogen reagents at low temperatures. The addition of E(SiMe(3))(2) to reaction mixtures of FcC{O}OCH(2)CH(2)ESiMe(3) (E = S, Se) and (Ph(3)P)(2)·AgOAc affords nanoclusters with approximate molecular formulas [Ag(36)S(9)(SCH(2)CH(2)O{O}CFc)(18)(PPh(3))(3)] (1), [Ag(100)Se(17)(SeCH(2)CH(2)O{O}CFc)(66)(PPh(3))(10)] (2), and [Ag(180)Se(54)(SeCH(2)CH(2)O{O}CFc)(72)(PPh(3))(14)] (3) as noncrystalline solids. Compositions were formulated on the basis of elemental analysis, high resolution transmission electron microscopy, and dynamic light scattering experiments. Solutions of these polyferrocenyl assemblies display a single quasi-reversible redox wave with some adsorption to the electrode surface as studied by cyclic voltammetry. With the smaller clusters 1, the addition of [Bu(4)N][HSO(4)] results in a shift of the reduction wave to less positive potentials than those of the complex in the absence of these oxoanions. No further shift is observed after the addition of approximately 1 equivalent of HSO(4)(-)/ferrocene branch. Cyclic voltammograms of the larger clusters 2 and 3 show the appearance of a new, irreversible wave at less positive potentials than the initial wave upon the addition of HSO(4)(-). The appearance of this new wave together with the disappearance of the reduction wave indicates a stronger interaction between the nanoclusters and the hydrogen sulfate anion.

Metal chalcogenide nanoclusters with 'tailored' surfaces via 'designer' silylated chalcogen reagents

Silylated chalcogen reagents are proven entry points for the preparation of ligand-stabilized, nanometre-sized metal-chalcogen clusters. More recently, these reagents have been developed to incorporate specific functionalities onto the surfaces of nanoclusters. The group 11 metals Cu and Ag in particular yield a wealth of structural types, the features for which are dependent on the nature of the surface chalcogenolate ligands. The content of this review focuses on complexes that have been structurally characterized by single-crystal X-ray diffraction studies and illustrates the ease by which these frameworks can be assembled.

Reversible phase transfer of (CdSe/ZnS) quantum dots between organic and aqueous solutions

Ttrioctylphosphine oxide (TOPO) stabilized CdSe/ZnS quantum dots (QD) were modified with 6-ferrocenyl-1-hexanethiol (FcHT) or 11-ferrocenyl-1-undecanethiol (FcUT) via ligand exchange. The presence of ferrocenyl thiol ligands on the surface of the QDs was proven by diffusion ordered NMR spectroscopy. Upon replacement of the initial TOPO ligand with ferrocene derivatives the emission of the QDs decreased. Phase transfer of ferrocene-modified QDs from organic solvents into water was achieved by complexation reactions with beta-cyclodextrin (beta-CD). The QDs coated with ferrocene thiols are soluble in nonpolar solvents and are transferred into the aqueous phase upon formation of host-guest complexes between the ferrocene units and the cavity of beta-CD. The reversibility of the phase transfer was probed by the addition of naphthalene and adamantane derivatives to the aqueous phase containing QD-[Fc-CD] adduct.