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Trioctylphosphine oxide

Trioctylphosphine oxide
Other names TOPO
Tri-n-octylphosphine oxide
Molecular formula [CH3(CH2)7]3PO
Molar mass 386.63 g/mol
Appearance White solid
CAS number [78-50-2]
Melting point 52 °C (325 K)
Flash point 110 °C (383 K)
Except where noted otherwise, data are given for
materials in their standard state (at 25°C, 100 kPa)
Infobox disclaimer and references

Trioctylphosphine oxide, frequently referred to simply as TOPO, is a chemical compound. TOPO, a tertiary alkylphosphines, can be used as an extraction or stabilizing agent. It is a stable white solid at room temperature.

It can be synthesized from phosphorus trichloride, or from a phosphine.

It is now frequently used as a capping ligand for quantum dots (e.g. CdSe quantum dots). In these cases, it stabilizes the nanoparticles in organic solvents. TOPO-coated quantum dots are typically soluble in chloroform, toluene, and (to a lesser extent) hexane.

Tri-n-octylphosphine oxide (TOPO) contains three octyl chains resulting in different conformational structures. Density functional theory (DFT) calculations performed at different levels of theory suggest that the lowest energy conformation of TOPO has C3 symmetry. The next most stable conformation is very close to possessing a plane of symmetry. In addition, there are at least 14 other conformations having no symmetry (not including optical isomers) which lie within 1 kcal/mol of the C3 geometry. The energies of these gauche conformations do not vary in a systematic fashion as the kink (dihedral angle θ=60°) moves towards the phosphorus along the octyl chain.

TOPO has a large permanent dipole moment resulting from the phosphorus-oxygen bond. The calculated vibrational frequencies of P=O bond do not correlate with the electronic density at the bond critical point.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Trioctylphosphine_oxide". A list of authors is available in Wikipedia.
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