Evolution of Spin-Crossover Transition in Hybrid Crystals Involving Cationic Iron Complexes [Fe(III)(3-OMesal2-trien)]+ and Anionic Gold Bis(dithiolene) Complexes Au(dmit)2 and Au(dddt)2

• Published in: Crystals (Basel) Vol. 8; no. 10; p. 382
• Main Authors: Spitsyna, Nataliya, Shvachko, Yuri, Starichenko, Denis, Lahderanta, Erkki, Komlev, Anton, Zorina, Leokadiya, Simonov, Sergey, Blagov, Maksim, Yagubskii, Eduard
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 03.10.2018
• Subjects: [Au(dmit)2]−, [Au(dddt)2]; Cations; Conformational analysis; coordination complexes; Coordination compounds; Coupling (molecular); Crossovers; Crystal structure; Dimers; Fe(III)(3-OMesal2-trien); Gold; Hydrogen bonding; ion-pair crystals; Iron; Ligands; Magnetic measurement; magnetic properties; magnetic susceptibility; magnetization; metal dithiolene complexes; Nitrates; Phase transitions; Physical properties; Physics; Rigid structures; Single crystals; spin-crossover transition; Stoichiometry; Superconducting quantum interference devices; Thermal cycling; Thermogravimetric analysis; X-ray diffraction; Germany; Russia
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst8100382

Hybrid ion-pair crystals involving hexadentate [Fe(III)(3-OMesal2-trien)]+ spin-crossover (SCO) cationic complexes and anionic gold complexes [Au(dmit)2]− (1) (dmit = 4,5-dithiolato-1,3-dithiole-2-thione) and [Au(dddt)2]− (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) were synthesized and studied by single-crystal X-ray diffraction, P-XRD, and SQUID magnetometry. Our study shows that both complexes have similar 1:1 stoichiometry but different symmetry and crystal packing. Complex 1 has a rigid structure in which the SCO cations are engaged in strong π-interplay with molecular surrounding and does not show SCO transition while 2 demonstrates a reversible transition at Tsco = 118 K in a much “softer”, hydrogen-bonded structure. A new structural indicator of spin state in [Fe(sal2-trien)]+ complexes based on conformational analysis has been proposed. Aging and thermocycling ruined the SCO transition increasing the residual HS fraction from 14 to 41%. Magnetic response of 1 is explained by the AFM coupled dimers S = 5/2 with J1 = −0.18 cm−1. Residual high-spin fraction of 2, apart from a contribution of the weak dimers with J12 = J34 = −0.29 cm−1, is characterized by a stronger interdimer coupling of J23 = −1.69 cm−1, which is discussed in terms of possible involvement of neutral radicals [Au(dddt)2].