The Conducting Spin-Crossover Compound Combining Fe(II) Cation Complex with TCNQ in a Fractional Reduction State

Yuri N Shvachko; Denis V Starichenko; Aleksander V Korolyov; Eduard B Yagubskii; Alexander I Kotov; Lev I Buravov; Konstantin A Lyssenko; Vladimir N Zverev; Sergey V Simonov; Leokadiya V Zorina; Olga G Shakirova; Lyudmila G Lavrenova

doi:10.1021/acs.inorgchem.6b01829

The Conducting Spin-Crossover Compound Combining Fe(II) Cation Complex with TCNQ in a Fractional Reduction State

Inorg Chem. 2016 Sep 6;55(17):9121-30. doi: 10.1021/acs.inorgchem.6b01829. Epub 2016 Aug 19.

Affiliations

¹ M. N. Miheev Institute of Metal Physics, Ural Branch of Russian Academy of Sciences , S. Kovalevskaya Street 18, Yekaterinburg 620137, Russia.
² Institute of Problems of Chemical Physics, Russian Academy of Sciences , Semenov Avenue 1, Chernogolovka, 142432 Moscow District, Russia.
³ A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences , Vavilov Street 28, Moscow 119991, Russia.
⁴ Institute of Solid State Physics, Russian Academy of Sciences , Ossipyan Street 2, Chernogolovka 142432, Moscow District, Russia.
⁵ Moscow Institute of Physics and Technology , Dolgoprudnyi, Moscow District 141700, Russia.
⁶ Komsomolsk-on-Amur State Technical University , Lenin Avenue 27, Komsomolsk-on-Amur 681013, Russia.
⁷ Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences , Lavrentyev Avenue 3, Novosibirsk 630090, Russia.

PMID: 27541570
DOI: 10.1021/acs.inorgchem.6b01829

Abstract

The radical anion salt [Fe{HC(pz)3}2](TCNQ)3 demonstrates conductivity and spin-crossover (SCO) transition associated with Fe(II) complex cation subsystem. It was synthesized and structurally characterized at temperatures 100, 300, 400, and 450 K. The compound demonstrates unusual for 7,7,8,8,-tetracyanoquinodimethane (TCNQ)-based salts quasi-two-dimensional conductivity. Pronounced changes of the in-plane direct-current resistivity and intensity of the electron paramagnetic resonance (EPR) signal, originated from TCNQ subsystem, precede the SCO transition at the midpoint T* = 445 K. The boltzmannian growth of the total magnetic response and structural changes in the vicinity of T* uniquely show that half [Fe{HC(pz)3}2] cations exist in high-spin state. Robust broadening of the EPR signal triggered by the SCO transition is interpreted in terms of cross relaxation between the TCNQ and Fe(II) spin subsystems.