Soumyajit Roy

En route from the mystery of molybdenum blue via related manipulatable building blocks to aspects of materials science

From a unique library containing molybdenum-oxide based building blocks/fragments under reducing conditions in aqueous solution a huge variety of nanoobjects, allowing specific reactions at well-defined positions, can be generated. This enables us to perform a new type of nanochemistry. Examples include: the well-known molecular big-wheel of the type {Mo-154} and its derivatives and the molecular big-sphere of the type {Mo-132}, the derivatives of which are considered here. In addition the by far largest structurally well characterized cluster with the shape of a lemon is also discussed. After solving the mystery of molybdenum blue, which was the starting point of this type of chemistry, it became evident that the acquired knowledge could be useful for advancing the frontiers of materials science

Multifunctional metal oxide based nanoobjects: spherical porous capsules/artificial cells and wheel-shaped species with unprecedented materials properties

Spherical and wheel-shaped molybdenum oxide based nanosized clusters exhibit unprecedented materials properties, due to the large number of active sites/functionalities on their outer and innermost surfaces, especially with respect to specific interactions with their environment.

Urea as 'deus ex machina' in giant molybdenum blue type cluster synthesis: an unusual hybrid compound with perspectives for related nano, supramolecular and extended structures.

The reaction of an aqueous solution of ammonium heptamolybdate with sodium dithionite and urea--a glue and cluster hydration shell destructing agent corresponding to its role in inclusion compound chemistry--at low pH value results in the formation of nanosized ring shaped molybdenum-oxide based clusters which in a short time get linked to chains.

Cover Picture: Angew. Chem. Int. Ed. 19/2002

The cover picture shows a novel hierarchic endohedral clusterization of H2O molecules in the form of a dodecahedron ((H2O)20, red), a further “mounted” dodecahedron (green), and a rhombicosidodecahedron ((H2O)60, yellow). The shell/host (Mo atoms blue, O red) is built up by 12 pentagonal {(Mo)Mo5} type building blocks (one is highlighted as a blue ring),which are connected by 30 MoV2 linkers with the consequence that 20 nanosized Mo9O9 pores/rings of classical crown ether quality are formed in which 20 guanidinium cations are encapsulated (C black, N green). The MoV2 type linkers are stabilized by PO2H2−/SO42− ligands (P/S purple). As the clusterization in the cavity takes place after filling the receptors/pores at the cluster surface with guests, a process is modeled by which a cell converts an extracellular molecular signal into a response. The representative red ring below the blue ring is marked out by the 60 H2O ligands coordinated to the pentagonal Mo units, which altogether form a rhombicosidodecahedron (not shown completely). As the geometric forms described are those of Platonic and Archimedean solids Plato and Archimedes feel involved. Further details are reported by A. Muller et al. on p. 3604u2009ff.

Visible light driven carbon dioxide reduction coupled with organic conversion by a functional ‘Janus’ catalyst based on Keplerate {Mo132}

Catalysts enabling CO2 reduction coupled with another organic reaction are rare. In this study, we report such a catalyst keplerate {Mo132}, which catalyses photochemical carbon dioxide reduction to formic acid coupled with organic transformation, i.e., hydration of phenylacetylene to acetophenone in visible light. It initially oxidizes water and injects the reducing equivalents for reduction of carbon dioxide at the same time, converting acetylenic group to ketone. Our designed redox Janus catalyst provides an inexpensive pathway to achieve carbon dioxide reduction as well as conversion of phenylacetylene to acetophenone, which is an industrially important precursor.