A Nanosized Molybdenum Oxide Wheel with a Unique Electronic‐Necklace Structure: STM Study with Submolecular Resolution

Abstract

The electrons go in two by two: Scanning tunneling microscopy (STM)/spectroscopy (STS), shows the Mo154 giant wheel cluster to have a unique localization of states within each of the 14 identical compartments forming its necklace‐type structure (see picture). Each compartment contains two delocalized electrons. These states make the system different from conventional quantum dots that have completely free electrons or excitonic states.

Insights into the Reaction Mechanism of Cyclohexane Oxidation Catalysed by Molybdenum Blue Nanorings

“…As MB presents a oxo-bridge system this gives rise to two intervalence bands [27], a band at high energy (low wavelength) due to a metal-tobridge charge transfer (MBCT) [28] and a band at lower energy due to a metal-to-metal charge transfer (MMCT). This phenomenon has been observed in oxo-bridged Ru complexes [29], and we tentatively assign the peak at 611 nm to a MBCT band and the peak at 654 nm 8 to a MMCT band. For the shoulder at 450 nm instead, this leads to an offset of 410 nn and in turn a band gap [30] of 3.02 eV, a value very similar to the band gap of thin films of MoO 3 (3.04 eV) [31].…”

“…A further feature of interest in this material is the presence of Mo 5+ -O-Mo 6+ units embedded into the nanoring structure [8], a property that we exploited showing that MB can be an efficient catalyst for the oxidation of cyclohexane [9]. In particular, MB had the interesting property to be is selective towards the formation of cyclohexanol rather than cyclohexanone and with minimal formation of adipic acid (the three major products of cyclohexane oxidation) [9].…”

Molybdenum blue nano-rings: an effective catalyst for the partial oxidation of cyclohexane

“…To date there has been limited progress in the characterization of the microstructure of these mixed-valency molybdenum compounds by electron microscopy. Nevertheless, highresolution TEM images acquired in these previous studies show poor correlation with the STM images obtained by Zhong et al, 6 as no discrete nano-ring structures were observed. While there has been considerable interest in the structure of MB nano-rings and their molecular assemblies, its use as a catalyst has not been considered in any great detail.…”

Selective Oxidation of Sulfides Catalyzed by the Nanocluster Polyoxomolybdate (NH4)12[Mo36(NO)4O108(H2O)16]

“…[20][21][22][23][24] In the majority of these cases, the molybdenum is usually present as Mo V and Mo VI and the catalysts exhibit significant electron hopping between the Mo V and Mo VI sites through Mo V -O-Mo VI bridging bonds, potentially representing materials that could be highly active towards selective redox chemistry. [25,26] As part of our ongoing study of the selective and green synthesis of sulfoxides, [27][28][29][30][31] we report herein a highly efficient, recyclable, and green method for the selective oxidation of a series of sulfides to the corresponding sulfoxides in excellent yields and selectivities under mild reaction conditions with the aid of the polyoxomolybdate nanocluster (NH 4 ) 12 16 ] as an efficient catalyst and urea hydrogen peroxide (UHP) as the oxidant. 16 ] salt.…”