Solvent-Induced Hysteresis Loop in Anionic Spin Crossover (SCO) Isomorph Complexes

Cuza, Emmelyne; Benmansour, Samia; Cosquer, Nathalie; Conan, Françoise; Gómez‐García, Carlos J.; Triki, Smaı̈l

doi:10.3390/magnetochemistry7060075

Cited by 3 publications

(3 citation statements)

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“…Similar to our findings (Figure ), excellent linear correlations of solid state T 1/2 with a TM (NCE) are also observed for the five literature families surveyed (Figure ). ,− …”

Section: Resultsmentioning

confidence: 99%

“…Plot showing excellent correlations of the coordination ability ( a TM ) of the NCE co-ligand (E = BH 3 , Se, and S) with the solid state T 1/2 for five sets of literature families: (green) [Fe II (L 5Me )(NCE) 2 ]; (pink) [Fe II (tppm)(NCE) 2 ] (two-step SCO was observed for all 3 complexes, so T 1/2 of the first step in the cooling mode is used here); (brown) [Fe II (L PZ ) 2 (NCE) 2 ]; (blue) {[(Tp)Fe III (CN) 3 ] 2 [Fe II (TPPO)] 2 [NCE] 2 }; (red) anionic [Fe(py 3 C–OEt)(NCE) 3 ] − …”

Section: Resultsmentioning

confidence: 99%

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Solution Spin Crossover Versus Speciation Effects: A Cautionary Tale

Sundaresan

Brooker

2023

Inorg. Chem.

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Two acyclic tetradentate Schiff base ligands, HL X–OH (X = H and Br), were synthesised by 2:1 condensation of either 2-pyridinecarboxaldehyde or 5-bromo-2-pyridinecarboxaldehyde and 1,3-diamino-2-propanol and then used to prepare six mononuclear complexes, [FeII(HL X–OH )(NCE)2], with three different NCE co-ligands (E = BH3, Se, and S). The apparent solution spin crossover switching temperature, T 1/2, of these 6 complexes, determined by Evans method NMR studies, is tuned by several factors: (a) substituent X present at the 5 position of the pyridine ring of the ligand, (b) E present in the NCE co-ligand, (c) solvent employed (P′), and (d) potentially also by speciation effects. In CD3CN, for the pair of NCE = NCBH 3 complexes, when X = H, the complex is practically LS (extrapolated T 1/2 ∼624 K), whereas when X = Br, it is far lower (373 K), which implies a higher field strength when X = H than when it is Br. The same trend, X = H results in a higher apparent T 1/2 than X = Br, is seen for the other two pairs of complexes, with E = Se (429 > 351 K, ΔT 1/2 = 78 K) or S (361 > 342 K, ΔT 1/2 = 19 K). For the family of three X = Br complexes, the change of E from BH3 (373 K) to Se (351 K) to S (342 K) leads to an overall ΔT 1/2(apparent) = 31 K, whereas the decreases are far more pronounced in the X = H family (BH3 ∼624 > Se 429 > S 361 K). Changing the solvent used from CD3CN to (CD3)2CO and CD3NO2, for [FeII(HL Br–OH)(NCE)2] with either E = BH3 or S, revealed excellent, and very similar, positive linear correlations (R 2 = 0.99) of increasing solvent polarity index P′ (from 5 to 7) with increasing apparent T 1/2 of the complex (E = BH3 gave T 1/2 300 < 373 < 451 K , ΔT 1/2 = 151 K; E = S gave T 1/2 288 < 342 < 427 K, ΔT 1/2 = 147 K). Several other solvent parameters were also correlated with the apparent T 1/2 of these complexes (R 2 = 0.74–0.96). Excellent linear correlations (R 2 = 0.99) are also obtained with the coordination ability (a TM) of the three NCE co-ligands with the apparent T 1/2 in both families of compounds, [FeII(HL X–OH )(NCE)2] where X = H or Br. The 15N NMR chemical shifts of the nitrogen atom in the three NCE co-ligands (direct measurement) show modest correlations (R 2 = 0.74 for L H–OH family and 0.80 for L Br–OH family) with the apparent T 1/2 values of the corresponding complexes.

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“…Similar to our findings (Figure ), excellent linear correlations of solid state T 1/2 with a TM (NCE) are also observed for the five literature families surveyed (Figure ). ,− …”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Solution Spin Crossover Versus Speciation Effects: A Cautionary Tale

Sundaresan

Brooker

2023

Inorg. Chem.

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“…The contribution by S. Triki et al at the University of Brest (France) and S. Benmanosur and C. J. Gómez-García at the University of Valencia (Spain), ref. [11], describes the synthesis and complete characterization of a rare anionic Fe(II) spin crossover (SCO) complex that shows a two-step SCO at around 170 and 298 K, as confirmed by crystallographic and magnetic studies. After complete de-solvation of the complex at around 400 K, the high temperature step shifts to lower temperatures and merges in only one gradual SCO at around 216 K.…”

Section: Editorialmentioning

confidence: 93%

Perspectives on Molecular Materials—A Tribute to Professor Peter Day

et al. 2021

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Gradual or Hysteretic Transition: Anion Effects on Cobalt(II) Spin Crossover Complexes

Sun,

Li,

Zhang

et al. 2024

Chin. J. Chem.

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Comprehensive SummaryTo better understand the impact of different anions on the structures and SCO properties of the CoII SCO complexes, six new complexes [Co(terpy‐CH2OH)2]A2·sol (terpy‐CH2OH = 4′‐(hydroxymethyl)‐2,2′;6′,2″‐terpyridine, A = Br– (1, sol = 1.5H2O), I– (2), N3– (3, sol = 2H2O), H3BCN– (4), OTf– (5), and TsO– (6, sol = 4H2O·CH3CN), have been synthesized and characterized. All six compounds consist of mononuclear [Co(terpy‐CH2OH)2]2+ cations and charge‐balancing anions that differ in size, shape, and hydrogen bonding capacity. Complexes 1, 2, 3, and 6 displayed incomplete gradual SCO transitions, whereas 4 and 5 exhibited abrupt hysteretic spin transitions with loops of 12 and 16 K (250.0—262.0 K for 4, and 370.0—386.0 K for 5, respectively), closely resembling our previously reported complexes with SCN– and SeCN– anions. The occurrence of the order‐disorder transition of the CH2OH groups and their transition temperatures are determined by the size and hydrogen bonding capability of the anions. Remarkably, the transition temperatures of complexes with H3BCN–, SCN–, OTf–, and SeCN– anions exhibit an upward trend as the size and mass of the anions increase, as confirmed through detailed single crystal structure analyses conducted in both high‐spin and low‐spin states for all four complexes.

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Solvent-Induced Hysteresis Loop in Anionic Spin Crossover (SCO) Isomorph Complexes

Cited by 3 publications

References 48 publications

Solution Spin Crossover Versus Speciation Effects: A Cautionary Tale

Solution Spin Crossover Versus Speciation Effects: A Cautionary Tale

Perspectives on Molecular Materials—A Tribute to Professor Peter Day

Gradual or Hysteretic Transition: Anion Effects on Cobalt(II) Spin Crossover Complexes

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