An unprecedented hetero-bimetallic three-dimensional spin crossover coordination polymer based on the tetrahedral [Hg(SeCN)₄]²⁻building block

Abstract

A new non-Hoffmann type of hetero-bimetallic HgII–FeII spin-crossover coordination polymer has been structurally and magnetically investigated.

Spin Crossover in a Series of Non-Hofmann-Type Fe(II) Coordination Polymers Based on [Hg(SeCN)3]− or [Hg(SeCN)4]2– Building Blocks

“…31 The T 0 value found for 2 is virtually the same as that found for the compound {Fe(bpe)[Hg-(SeCN) 4 ]} n mentioned above. 23 Due to the extremely low yield of complex 3, we could only study its structure at 119 K, which shows that the compound is in the LS state at this temperature. Although this derivative can foreseeably present SCO behavior, we were unable to measure either the thermal dependence of its magnetic properties or its structure at room temperature to confirm it.…”

“…However, the structurally closely related ligand L = tvp produces exclusively the 3D CP where the [Hg(SeCN) 4 ] 2− centers act as tetraconnecting nodes similarly to the previously reported bpe derivative (bpe = trans-1,2-bis(4-pyridyl)ethane). 23 These results confirm that the discrimination between the 2D or 3D CP structures depends on the metrics and probably the flexibility of L. Then, with this in mind, we have included, as an additional variable, the influence of the coordination topology of L on the nature of the resulting CP. Thus, by introducing the 3,3′-positioned pyridyl ligands L = 3,3′-bipy and 3,3′-azpy, with possible cis or trans coordination modes, two other 3D non-Hofmann-type CPs were successfully synthesized using the same diffusion method.…”

“…100 K is a reasonable estimation for the complete SCO, which is close to that found for the homologous {Fe(bpe)[Hg(SeCN) 4 ]} n . 23 In order to estimate the thermodynamic parameters associated with the SCO behavior in 1 and 2, the spin transition was simulated using the mean-field regular solution model described by eq 1 25 (Figure S11)…”

“…Similarly to the monodentate precursor XCN − anionic ligands, the ligand-field strength of the tetradentate [Hg(XCN) 4 ] 2− building blocks is larger for X = Se than for X = S. In particular, {Fe(bpe)[Hg(SeCN) 4 ]} n displays complete thermal-and light-induced SCO behavior. 23 We also showed previously that the lability of the [Hg(SCN Compound 3 is a byproduct in the synthesis of 4 but in contrast to the latter is an LS complex at low temperatures and most probably is also a SCO system.…”

A rare octacoordinated mononuclear iron(III) spin-crossover compound: synthesis, crystal structure and magnetic properties

“…They are among the best materials for showing electronic bi-stability making them prime candidates for molecular electronic and spintronic devices (Jin et al, 2019;Ide et al, 2017;Hayami et al, 2001;Pavlik et al, 2020;Kahn & Martinez, 1998). In comparison to other types of possible molecular switches (Boonprab et al, 2019;Hayami et al, 2001), SCO transition-metal complexes based on Fe II can easily switch between high-spin (HS, S = 2) and low-spin (LS, S = 0) states under external perturbation, such as temperature, physical and chemical pressure, or magnetic or electrical switching (Trzop et al, 2016;Zhang et al, 2017Zhang et al, , 2018Lan et al, 2019;Jin et al, 2019;Ide et al, 2017;Hayami et al, 2001;Pavlik et al, 2020;Kahn & Martinez, 1998;Murphy et al, 2017), and thus show great potential applications in memory devices, sensors, etc. (Turanova et al, 2020;Kahn & Martinez, 1998).…”