[Fe(abpt)₂(NCSe)₂] polymorph A: structural studies into the spin crossover behaviour

Abstract

Crystallographic and UV-Vis analysis of the thermal spin-transition in [Fe(abpt)2(NCSe)2], polymorph A, is presented alongside LIESST and high pressure structures.

A Rare Example of a Complete, Incomplete, and Non-Occurring Spin Transition in a [Fe2L3]X4 Series Driven by a Combination of Solvent-and Halide-Anion-Mediated Steric Factors

“…Although interestingly, close analysis of the crystal structures obtained revealed an interesting trend in the manner with which various crystallographic parameters (cell volume, Fe–N distance, a , b , c , β, packing coefficient, and length of intermolecular interactions) evolve with temperature (Table ), appearing to change in a way that very closely resembles the change in the magnetic susceptibility of the material. This trend is commonly associated with SCO materials . As can be seen in Figures , , , and S4–S6, while there is no phase change and overlapping structural analysis of single crystal models indicates very little change in confirmation of the helicate architecture (Figures S13–S15), these various crystallographic parameters appear to be changing in a very similar “two-step” profile.…”

“…This trend is commonly associated with SCO materials. 37 As can be seen in Figures 3, 4, 5, and S4−S6, while there is no phase change and overlapping structural analysis of single crystal models indicates very little change in confirmation of the helicate architecture (Figures S13−S15), these various crystallographic parameters appear to be changing in a very similar "two-step" profile. Such a double sigmoidal nature of the change in crystallographic parameters with temperature may explain the two-step nature of the molar magnetic susceptibility.…”

Structural studies into the spin crossover behaviour of Fe(abpt)2(NCS)2 polymorphs B and D

“…41 Such difference in the behaviour under different types of irradiation have the potential to be useful for tuning responses in applications. It is also worth noting that [Fe(abpt) 2 (NCSe) 2 ] has been found to have two polymorphs A 37,43 and B 42 which are isostructural with the respective [Fe(abpt) 2 (NCS) 2 ] polymorphs. The known spin crossover behaviour is also very similar for the NCS and NCSe polymorphs.…”

Extension of Azine-Triazole Synthesis to Azole-Triazoles Reduces Ligand Field, Leading to Spin Crossover in Tris-L Fe(II)

“…Generic 1,2,4-triazole showing ring numbering (top left), ditopic PMRT (4-R-substituted-3,5-bis­{[(2-pyridylmethyl)­amino]­methyl}-4 H -1,2,4-triazole) /PSRT (4-R-substituted-3,5-bis­{[(2-pyridylmethyl)­sulfanyl]­methyl}-4 H -1,2,4-triazole) (top middle) ,− and related thia-/oxazole ligands PMTD (2,5-bis­[(2-pyridylmethyl)­amino]­methyl-1,3,4-thiadiazole)/ PMOD (2,5-bis­{[(2-pyridylmethyl)­amino]­methyl}-1,3,4-oxadiazole) (top right). − ditopic R at ligands L 2/4pym‑meta/para (1, n -bis­(4-isobutyl-5-(pyrimidin-2/4-yl)-4 H -1,2,4-triazol-3-yl)­benzene (middle), and R dpt (4- R -substituted 3,5-di­(2-pyridyl)­triazole) (bottom left) as well as monotopic R at ligands (bottom), either azine -substituted L azine (bottom middle) ,,− or the new azole -substituted (bottom right, box) versions made and used in this study, L 4NMeIm and L 4SIm .…”

“…1,2,4-Triazole-based ligands have been targeted by many researchers, as 1,2,4-triazoles are readily functionalized at some or all of the C 3 , C 5 , and N 4 positions of the triazole ring (Figure ) and have generated many interesting complexes of a wide range of metal ions. ,,− Of interest herein is that many such 1,2,4-triazole based ligands, including the bis-terdentate PMRT/PSRT (Figure , top middle) ,− and the related thia-/oxa-diazoles PMTD/PMOD (Figure , top right), − as well as the bis- or monobidentate R dpt /R at ligand types (Figure , bottom), ,,− are reported in the literature to form SCO-active iron­(II) complexes.…”