Jump to main content
Jump to site search

Issue 39, 2012
Previous Article Next Article

Relating highly distorted Jahn–Teller MnO6 to colouration in manganese violet pigments

Author affiliations

Abstract

‘Manganese violet’ pigments have been known for over 150 years, but are receiving renewed interest due to their non-toxicity and earth-abundant components. For the first time we report here a detailed study into the structural aspects that define the sought-after pigment properties of these materials. This work identified two polymorphs, designated as α- and β-NH4MnP2O7 that provide the strong colouration and compared them to a commercially available sample. Rietveld analysis of neutron powder diffraction data indicated that the α-polymorph crystallised in space group P21/c (a = 7.4252(3) Å, b = 9.6990(4) Å, c = 8.6552(4) Å and β = 105.627(3)°) and exhibited a highly distorted MnO6 coordination sphere. The apparent [2 + 2 + 2] distortion gives rise to the optical properties and appears to be driven, in part, by a “plasticity effect” in the Mn coordination induced by the pyrophosphate ligand. A second polymorph β-NH4MnP2O7 was found to crystallise in space group P[1 with combining macron] (a = 8.4034(6) Å, b = 6.1498(4) Å, c = 6.1071(4) Å, α = 104.618(5)°, β = 100.748(5)° and γ = 96.802(6)°) and possessed similarly distorted MnO6 octahedra, but was found to differ from α-NH4MnP2O7 in the relative dimensions of the intersecting framework tunnels that contained the ammonium cations. UV-visible spectroscopy was used to characterise optical behaviour and a combination of TGA-MS and in situ high temperature X-ray powder diffraction were used to determine thermal decomposition pathways.

Graphical abstract: Relating highly distorted Jahn–Teller MnO6 to colouration in manganese violet pigments

Back to tab navigation

Supplementary files

Publication details

The article was received on 11 Jun 2012, accepted on 28 Aug 2012 and first published on 29 Aug 2012


Article type: Paper
DOI: 10.1039/C2JM33731B
Citation: J. Mater. Chem., 2012,22, 21110-21116
  •   Request permissions

    Relating highly distorted Jahn–Teller MnO6 to colouration in manganese violet pigments

    Y. Begum and A. J. Wright, J. Mater. Chem., 2012, 22, 21110
    DOI: 10.1039/C2JM33731B

Search articles by author

Spotlight

Advertisements