John F. Corrigan

Molecular nanocluster analogues of CdSe/ZnSe and CdTe/ZnTe core/shell nanoparticles

The ternary II–II′–VI nanoclusters [(N,N′-tmeda)5Zn5Cd11E13(EPh)6(thf)n] (1, E = Se, n = 2; 2, E = Te, n = 1) have been synthesized by the reaction of bis(trimethylsilylchalcogenolate)zinc(II) complexes in the presence of PhESiMe3 and solubilizing phosphine ligands. Structural characterization of the complexes by X-ray crystallography revealed that the clusters consist of CdE cores whose surfaces are stabilized by [(N,N′-tmeda)5ZnE2] units, and hence can be described as molecular analogues of core/shell nanoparticles. The optical properties of the clusters exhibit the effects of quantum confinement and are luminescent at room temperature with emission occurring near the absorption edge. Solid-state thermal decomposition of 1 and 2 results in the formation of ternary ZnCdE materials with the same metal stoichiometry as the cluster precursors.

Ferrocene-based trimethylsilyl chalcogenide reagents for the assembly of functionalized metal-chalcogen architectures

The ferrocene-based trimethylsilyl chalcogenide reagents [FcC(O)OCH(2)CH(2)ESiMe(3)] (2, E=S, 3 E=Se, Fc=[Fe(η(5)-C(5)H(5))(η(5)-C(5)H(4))]) and [FcC(O)NHCH(2)CH(2) SSiMe(3)] (8b) have been synthesized. The reagents were reacted with solubilized transition-metal acetates to yield functionalized complexes and clusters, including the spherical nanocluster [Ag(14)S{SCH(2)CH(2)O(O)CFc)}(12)(PPh(3))(6)] (11, PPh(3) =triphenylphosphine). The complexes were characterized by NMR spectroscopy and X-ray crystallography. The electrochemical behavior of the complexes was explored by cyclic voltammetry and each displayed a single quasi-reversible redox wave with some adsorption to the electrode surface.

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.

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.

Synthesis and structural characterisation of new copper–tellurium clusters: TeBun(SiMe3) as a source of RTe– and Te2– ligands

Reactions of cobalt(II) and copper(I) salts with the functionalised reagents alkyl- and aryl-(trimethylsilyl)tellurium have been explored. The silylated reagents are found to be an excellent source of RTe– and Te2– ligands alike in high-nuclearity transition metal–tellurium clusters and the products isolated from the reaction mixtures have been structurally characterised by single-crystal X-ray analyses: [Co6(µ3-Te)8(PPh2Prn)6]1,[Cu11(µ3-TeBun)7(µ4-TeBun)2(µ7-Te)(PPh3)5]2,[Cu18(µ3-TeBun)6Te6(PPrn3)8]3,[Cu58Te32(PPh3)16]4 and [Cu23Te13(PEt3)12]5 have been synthesised. The formation of the complexes is highly dependent on the ancillary phosphine used. Cluster 1 consists of a non-bonded octahedral array of Co atoms with eight tellurium ligands capping the open Co3 faces. Complexes 2–4 possess layered structures composed of Te atoms with Cu occupying peripheral and interlayer sites. The Te atoms in 5 form a body-centred icosahedron, with an overall near-spherical cluster framework.

A molecular precursor approach for the synthesis of composition-controlled ZnxCd1−xS and ZnxCd1−xSe nanoparticles

Ternary ZnxCd1−xS and ZnxCd1−xSe nanoparticles have been synthesized using a low temperature molecular precursor approach. The co-injection of silylated metal chalcogenolate complexes [(N,N′-TMEDA)Zn(ESiMe3)2] (E = S, 1; E = Se, 2) and [(N,N′-TMEDA)Cd(ESiMe3)2] (E = S, 3; E = Se, 4) to solutions of (N,N′-TMEDA)M(OAc)2 (M = Zn, Cd) in THF resulted in the formation of nanocrystalline quantum dots with particle sizes in the 2–3 nm range. Nanoparticles with Zn mole fractions (x) ranging from 0.95 to 0.05 can be achieved via manipulation of the reaction stoichiometry of 1(2) and 3(4). The size uniformity of the ternary nanoparticles permits control of the absorption properties by changing the metal ion composition. UV-visible and NMR spectroscopy, thermogravimetric analysis as well as X-ray and electron diffraction studies provide substantial evidence that the Zn(II) and Cd(II) ions are homogeneously mixed both within the cores of the nanoparticles and at the particle surfaces. Further control of the optical properties of the ternary materials was achieved via the growth of the particles in hot hexadecylamine while maintaining the Zn/Cd ratio.

Functionalizing the surface of II–VI clusters: redox active centres on the adamantoid complex [Cd4Cl4{μ-(SeC5H4)Fe(C5H5)}6]2−

Trimethylsilylselenoferrocene 1 has been prepared in good yield. The reactive silyl group on 1 is used as a driving force for the synthesis [Cl4Cd4[mu2-Se(C5H4)Fe(C5H5))6]2- 2, a Cd4Se6 adamantoid cluster with six surface ferrocenyl groups.

From Molecule to Materials: Crystalline Superlattices of Nanoscopic CdS Clusters

Make way for a superlattice! A crystalline 3D superlattice of 2.3 nm molecular CdS nanoclusters was prepared from a convenient mononuclear cadmium thiophenolate precursor. HRTEM and STEM tomography show highly crystalline repetition of monodisperse frameworks. This combined with elemental and thermogravimetric analyses suggests an approximate formula [Cd(130)S(103)(SPh)(54)].

A Homoleptic Silver-Ferrocenylselenolate: Synthesis and Characterization of [Ag4(fcSe2)3]2−

Abstract1,1′-Bis(trimethylsilylseleno)ferrocene has been used to synthesize the anionic cluster [Ag4(fcSe2)3]2−