Unique Colours of 3d-Transition-Metal-Substituted Lyonsite Molybdates and Their Derivatives: The Role of Multiple Coordination Geometries and Metal-to-Metal Charge Transfer

Laha, Sourav and Natarajan, Srinivasan and Gopalakrishnan, Jagannatha (2016) Unique Colours of 3d-Transition-Metal-Substituted Lyonsite Molybdates and Their Derivatives: The Role of Multiple Coordination Geometries and Metal-to-Metal Charge Transfer. In: EUROPEAN JOURNAL OF INORGANIC CHEMISTRY (24). pp. 3883-3891.

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Abstract

We describe the synthesis, crystal structures, and optical absorption spectra/colours of 3d transition-metal-substituted lyonsite-type oxides Li3Al1-xMxIII(MoO4)(3) (0<x1.0; M-III = Cr, Fe) and Li3-xAl1-xM2xII(MoO4)(3) (0<x1.0; M-II = Co, Ni, Cu). The oxides were readily synthesized by the solid-state reaction of stoichiometric mixtures of the constituent binaries at around 700 degrees C in air. The crystal structures determined by Rietveld refinement of PXRD data revealed that in the smaller trivalent-metal-substituted lyonsite oxides, the M-III ions occupy the octahedral (8d, 4c) sites and the lithium ions occur exclusively at the trigonal-prismatic (4c) site in the orthorhombic (Pnma) structure. On the other hand, larger divalent-metal (Co-II/Cu-II)-substituted derivatives show occupancy of the Co-II/Cu-II ions at both the octahedral and trigonal-prismatic sites. We have investigated the colours and optical absorption spectra of Li3Al1-xMxIII(MoO4)(3) (M-III = Cr, Fe) and Li3-xAl1-xM2xII(MoO4)(3) (M-II = Co, Ni, Cu) and interpreted the results in terms of the average crystal field strengths experienced by M-III/M-II ions in multiple coordination geometries. We have also identified the role of metal-to-metal charge transfer (MMCT) from the partially filled transition metal 3d orbitals to the empty Mo 4d orbitals in the resulting colours of these oxides.

Item Type:	Journal Article
Publication:	EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
Additional Information:	Copy right for this article belongs to the WILEY-V C H VERLAG GMBH, POSTFACH 101161, 69451 WEINHEIM, GERMANY
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	28 Oct 2016 07:22
Last Modified:	28 Oct 2016 07:22
URI:	http://eprints.iisc.ac.in/id/eprint/55163

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