Spin crossover in iron(II) complexes of 3,4,5-tri-substituted-1,2,4-triazole (Rdpt), 3,5-di-substituted-1,2,4-triazolate (dpt − ), and related ligands

Predictable Electronic Tuning By Choice of Azine Substituent in Five Iron(II) Triazoles: Redox Properties and DFT Calculations

“…All compounds except 5 ⋅4 H 2 O have very low χ M T values, 0.04–0.25 cm 3 ⋅K mol −1 , from 300 to 50 K (Figure S6), consistent with being in the LS state, as expected . The exception, 5 ⋅4 H 2 O (the complex of L 4pyrimidine ), has significantly higher χ M T values, 1.24–1.34 cm 3 ⋅K mol −1 (Figure S6), across the temperature range studied, consistent with the presence of a temperature‐independent HS fraction of approximately 0.35 . In contrast, for the solvatomorph 5 ⋅4 CH 2 Cl 2 , the LS state was observed by crystallography (see above).…”

“…The average Fe−N bond length in the four complexes at 100 K ranges from 1.941 to 1.965 Å, consistent with LS iron(II) centers . The octahedral distortion parameter Σ for all complexes (59.7–62.5°) falls within the expected range for LS iron(II) centers (42.5–65.7°),, except 5 ⋅4 CH 2 Cl 2 (69.9°) which is slightly above this range, but is still lower than that seen for HS centers (77.9–101.1°) ,. In all four structures, the cationic complexes interact with neighboring cationic complexes through non‐classical CH⋅⋅⋅N (uncoordinated) hydrogen bonds as well as CH⋅⋅⋅π and π⋅⋅⋅π contacts, and with the anions and lattice solvent molecules through a variety of types of contacts (see SI, Sections S1.3 and S1.5).…”

Abrupt Spin Crossover Behavior in a Linear N1,N2-Triazole Bridged Trinuclear Fe(II) Complex

“…Currently, special attention is given to SCO compounds exhibiting pronounced cooperative behavior. Here, the mononuclear system [Fe(bpp) 2 ] 2+ (bpp = 2,6-di{pyrazol-1-yl}pyridine) [1][2][3][4], as well as the triazole-based mono-/bi-nuclear [Fe 2 (PMAT) 2 ] 4+ system [5][6][7][8], are among the most frequently reported compounds. Recently, we could enlarge the family of binuclear systems showing multiple SCO steps with reports on thiadiazole and oxadiazole complexes for which the cooperativity was studied in detail [9,10].…”

“…This family of compounds shows the attempt and endeavor to explore the famous 1D coordination polymers of general formula [Fe(Rtrz) 3 ](X) 2 (Rtrz = 4-subsitituted-1,2,4-triazole, X − = standard monoanions): some of which displayed wide thermal hysteresis loops around room temperature [11][12][13][14][15][16]. Compared to the typical molecular system mentioned above [1][2][3][4][5][6][7][8][9][10], the triazole-based compounds bear benefits of expanding the discrete nuclearities to multinuclear or 1D polymeric complexes, which is of vital importance…”

Tuning the Spin States of Two Apical Iron(II) Ions in a Pentanuclear Iron(II) Cluster Helicate through the Choice of Anions

“…In this paper, guided by the supermolecular self-assembly principle, we selected a bptH ligand with two bidentate chelating sites, mainly because this ligand should also provide an appropriate ligand field favoring the occurrence of SCO [4,[22][23][24][25][26]; according to past literature, this kind of ligand could probably construct a multi-nucleus iron(II) ion ligand [27], and this accorded with our design concept of combining the spin-crossover nature and magnetic exchange to study spintronics. We used the self-assembly of this ligand with iron(II) ions with an octahedral coordination habit to obtain three Fe 5 cationic clusters [{Fe II (µ-bpt) 3 .…”