Water-in-Oil Microemulsion Preparation and Characterization of Cs2[Mo6X14]@SiO2 Phosphor Nanoparticles Based on Transition Metal Clusters (X = Cl, Br, and I)
✍ Scribed by F. Grasset; F. Dorson; S. Cordier; Y. Molard; C. Perrin; A.-M. Marie; T. Sasaki; H. Haneda; Y. Bando; M. Mortier
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 391 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0935-9648
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✦ Synopsis
Much research has been devoted to molybdenum octahedral clusters Mo 6 since the discovery of the A x Mo 6 Y 8 solidstate series (Y = S, Se, Te) in the early 1970s. [1] Indeed, their interesting physical properties and potential applicationse.g., superconductivity at high critical field, thermoelectric, catalysis, or redox intercalation processes -have stimulated the research of many groups. [2] They are based on [(Mo 6 L i 8 )L a 6 ] units (where L a is the apical ligand and L i the inner ligand), which constitute the basic building blocks in molybdenum octahedral cluster chemistry. [3] The Mo 6 cluster is face-capped by eight inner ligands (L i ) and is additionally bonded to six apical ligands (L a ) (Fig. 1). The physical properties of Mo 6 solid-state compounds are related to the number of electrons available for metal-metal bonding within the cluster (valence electron count, VEC) and to the strength of interaction between the units. Mo-centered electrons are located on twelve metal-metal bonding molecular orbitals of the molecular orbital diagram. Their full occupation leads to a closed-shell configuration with a VEC of 24. [4] In the A x Mo 6 Y 8 series, the units are strongly interconnected by L i-a /L a-i chalcogen bridges, leading to band structures and transport properties with the possibility of VEC values lower than 24. Halogen ligands favor the formation of solid-state molecular compounds based on [Mo 6 X i 8 X a 6 ] 2-(X = Cl, Br, I) units with VEC values of 24 that can be discrete or poorly interconnected within the solid. [5][6][7] The disssolution of inorganic solid-state halide precursors affords nanometric [Mo 6 X 14 ] 2-anionic units that exhibit interesting structural, photophysical, and redox properties [8,9] that can be used for the formation and organization of supramolecular assemblies as well as hybrid materials. Hybrids can be synthesized either by the grafting of functional donor ligands in apical position or through the association of anionic cluster units with organic or organometallic cations by cation metathesis or electrochemical techniques. [10] The large emission region of the [Mo 6 X 14 ] 2-anion in the red and near infrared (580-900 nm) is particularly interesting for biotechnology applications as it is selectively transmitted through tissues owing to the relatively low absorption at these wavelengths. [11] Anionic Mo 6 cluster units are usually associated with alkali counter cations within inorganic solids. Indeed, the use of inorganic cluster compounds as luminescent dyes, for instance in bio-imaging strategies, presupposes that both clusters and counter cations are embedded in an inert matrix in order to avoid ionic diffusion, oxidization of the cluster, or apical ligand exchanges in aqueous media, which will precipitate the cluster as a hydroxo species. For this purpose, we have chosen a novel synthesis strategy in cluster chemistry in order to prepare Cs 2 Mo 6 X 14 @SiO 2 nanoparticles based on both [Mo 6 X 14 ] 2-anionic cluster units and Cs + cations COMMUNICATION