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The Solid Solutions (Per)2[PtxAu(1−x)(mnt)2]; Alloying Para- and Diamagnetic Anions in Two-Chain Compounds

Matos, M. ; Bonfait, G. ; Santos, I. C. ; Afonso, M. ; Henriques, R. T. ; Almeida, M.

Magnetochemistry Vol. 3, Nº 3, pp. 1 - 13, April, 2017.

ISSN (print): 2312-7481
ISSN (online): 2312-7481

Journal Impact Factor: 2,690 (in )

Digital Object Identifier: 10.3390/magnetochemistry3020022

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Abstract
The α-(Per)2[M(mnt)2] compounds with M = Pt and Au are isostructural two-chain solids that in addition to partially oxidized conducting perylene chains also contain anionic chains that can be either paramagnetic in the case of M = Pt or diamagnetic for M = Au. The electrical transport and magnetic properties of the solid solutions (Per)2[Ptx-Au(1−x)(mnt)2] were investigated. The incorporation of paramagnetic [Pt(mnt)2] impurities in the diamagnetic chains, and the effect of breaking the paramagnetic chains with diamagnetic centers for the low and high Pt range of concentrations were respectively probed. In the low Pt concentration range, there is a fast decrease of the metal-to-insulator transition from 12.4 K in the pure Au compound to 9.7 K for x = 0.1 comparable to the 8.1 K in the pure Pt compound. In the range x = 0.50−0.95, only β-phase crystals could be obtained. The spin-Peierls transition of the pure Pt compound, simultaneous with metal-to-insulator (Peierls) transition is still present for 2% of diamagnetic impurities (x = 0.98) with transition temperature barely affected. Single crystal X-ray diffraction data obtained a high-quality structural refinement of the α-phase of the Au and Pt compounds. The β-phase structure was found to be composed of ordered layers with segregated donors and anion stacks, which alternate with disordered layers. The semiconducting properties of the β-phase are due to the disorder localization effects.