Abstract
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].
Highlights
Octahedral complexes with d4 -d7 metal ions can demonstrate spin-crossover (SCO) transition under external factors such as temperature, pressure, and electromagnetic radiation [1,2,3]
Polyfunctional compounds combining the conductivity and the spinthe spin-crossover transition have been highlighted in connection with spin-dependent transport and crossover transition have been highlighted connection spin-dependentconducting transport and single single molecular switching
We report synthesis, crystal structure, and magnetic properties of [Fe3+
Summary
Octahedral complexes with d4 -d7 metal ions can demonstrate spin-crossover (SCO) transition under external factors such as temperature, pressure, and electromagnetic radiation [1,2,3]. 2S2) and present electron system as intensively a planar central core different formal oxidation states This complex has been studied asM(C a component of molecular conductors [10,11,12]. SCO and complexes could undergo phase transition, andthe combining components in one crystal metal dithiolene complexes could undergo phase transition, and combining two components in one might give rise to a novel molecular material with exotic phenomena. 2 -trien)][Ni(dmit)2 ] showing a cooperative spin transition behavior with a wide a simple salt [Fe(sal a cooperative spin transition behavior a wide These results convinced us that metal bis(dithiolene) anionic and [M(dddt)2 ] complexes [12] might be promising candidates for enhancing cooperativity in SCO and [M(dddt).
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