SCIENTIFIC HIGHLIGHTS

New facets of molecular conductors

Molecular conductors still have many uncovered facets like silver-based single molecule metals and anilate-based small polaron hopping conductors

The field of molecular conductors continuously offers new surprises and accomplishments because of the broad tunability range offered by their molecular components. Two of these still uncovered features are the recent preparation of silver-based ambient pressure single molecule metals and anilate-based new two-dimensional semiconductors.

Based on the properties of the two-band conductors it was predicted that stable metals without any doping could exist. This prediction was first confirmed by the preparation of Ni[tmdt]2, a 3D molecular metal. The more challenging preparation of a stable 1D or pseudo-1D metal has been more involved. As a result of a long term experimental-theoretical collaboration between the groups of D. Lorcy (Rennes) and E. Canadell (ICMAB) in order to design the necessary structural and electronic requirements it has been finally possible to prepare and characterize, the first single component ambient pressure stable metal built from chains of neutral radicals, [Au(Me-thiazdt)2]. This system is immune to the ubiquitous Mott and Peierls type instabilities and keeps the room temperature metallic conductivity down to very low temperatures.

The coexistence of electrical conductivity and magnetic ordering in mixed valence FeII/FeIII two-dimensional oxalate-based coordination polymers has recently stimulated a large interest. Up to now the oxalate-based materials were found to be poor conductors. However the related anilate-based systems are very good semiconductors, opening the way towards the preparation of multifunctional conducting materials based on these extended coordination materials. As a first step in the way to elaborate a simple and predictive model helpful in the search for new systems, we have proposed a small polaron hopping Mott-Marcus based approach which can be easily extended to other materials and provides a simple explanation of the conductivity differences.

Authors:
Yann Le Gal,1 Thierry Roisnel,1 Pascale Auban-Senzier,2 Nathalie Bellec,1 Jorge Íñiguez,3 Enric Canadell,4 Dominique Lorcy, 1 Suchithra Ashoka Sahadevan,5,6 Alexandre Abhervé,5 Noemi Monni,6 Cristina Sáenz de Pipaón,7 José R. Galán-Mascarós,7,8 Joao C. Waerenborgh,9 Bruno J. C. Vieira,9Sébastien Pillet,10 El-Eulmi. Bendeif,10 Pere Alemany,11 Maria L. Mercuri,6 Narcis Avarvari5

Affiliations:
1Université de Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, France
2Laboratoire de Physique des Solides UMR 8502, CNRS-Université de Paris-Sud, France
3 Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), Luxembourg
4 Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain
5Laboratoire MOLTECH-Anjou UMR 6200, UFR Sciences, CNRS, Université d’Angers, France
6Dipartimento di Scienze Chimiche e Geologiche, Universitá degli Studi di Cagliari,  Italy
7 Institute of Chemical Research of Catalonia, BIST, Spain
8 ICREA, Spain
9 Centro de Ciéncias e Tecnologias Nucleares, Instituto Superior Técnico, Universidade  de Lisboa, Portugal
10 Université de Lorraine, CNRS, France
11 Departament de Ciència de Materials i Química Física and Institut de Química Teórica i Computacional (IQTCUB), Universitat de Barcelona, Spain

Publications:
[1] Stable metallic state of a neutral radical single-component conductor at ambient pressure.
Am. Chem. Soc. 140, 6998-7004 (2018)
DOI: 10.1021/jacs.8b03714
[2] Conducting Anilate-Based Mixed-Valence Fe(II)Fe(III) Coordination Polymer: Small-Polaron Hopping Model for Oxalate-Type Fe(II)Fe(III) 2D Networks
Am. Chem. Soc. 140, 12611-12621 (2018)
DOI: 10.1021/jacs.8b08032

Figure:
Temperature dependence of the conductivity (left) and Fermi surface (right) of the single component ambient pressure stable metal, [Au(Me-thiazdt)[2].

 

 

Acknowledgments

The work in Bellaterra was supported by MINECO (Spain) through grant FIS2015-64886-C5-3-P as well as the Severo Ochoa Centers of Excellence Program under grant SEV-2015-0496 and by Generalitat de Catalunya (2017SGR1506). J.I. is funded by the Luxembourg National Research Fund through the PEARL project (grant FNR/P12/4853155/Kreisel COFERMAT). We thank T. Guizouarn for magnetic susceptibility measurements and P. Alemany for assistance with the calculations.

The work in France was supported by the CNRS, the University of Angers, the Erasmus program (mobility grant to N.M.), the RFI Regional project LUMOMAT (grant to A.A., project ASCO MMM), and the PIA project “Lorraine Université d'Excellence” (reference ANR-15-IDEX-04-LUE). This work was supported in Italy by the Fondazione di Sardegna-Convenzione triennale tra la Fondazione di Sardegna e gli Atenei Sardi, Regione Sardegna-L.R. 7/2007 annualitá 2016-DGR 28/21 del 17.05.2015 “Innovative Molecular Functional Materials for Environmental and Biomedical Applications” and INSTM. Work in Spain was supported by the Spanish Ministerio de Economía y Competitividad (Grants FIS2012-37549-C05-05, FIS2015-64886-C5-4-P, CTQ2015- 64579-C3-3-P, and CTQ2015-71287-R) and Generalitat de Catalunya (2014SGR301, 2017SGR797, and XRQTC and the CERCA program). E.C. acknowledges support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2015-0496. J.C.W. and B.J.C.V. acknowledge Fundaçao para a Ciência e a Tecnologia (FCT, Portugal) through the project UID/Multi/04349/2013

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