A proficient multivariate approach for iron(ii) spin crossover behaviour modelling in the solid state

Abstract

Iron(II) bis-pyrazolilpyridyl (bpp-R) complexes [Fe(bpp-R)2](X)2·solvent, R = substituent and X– = anion, can undergo spin transition from high (S = 2, HS) to low spin (S = 0, LS), being...

A Survey of the Angular Distortion Landscape in the Coordination Geometries of High-Spin Iron(II) 2,6-Bis(pyrazolyl)pyridine Complexes

“…Spin-crossover (SCO) materials − continue to be of great interest in fundamental studies of crystal engineering; , as components in switchable multifunctional materials; − and for their applications in macroscopic and nanoscale devices. − Iron­(II) complexes of 2,6-di­(pyrazol-1-yl)­pyridine (bpp; Chart ) and its derivatives are some of the most widely studied compounds for SCO research. − Their popularity reflects that substituted bpp derivatives are readily accessible using appropriately substituted synthetic reagents, or by functional group transformations at preformed bpp precursors . The electronic and steric character of those substituents predictably influences the spin states of substituted [Fe­(bpp) 2 ] 2+ derivatives in solution − and, to a degree, in the solid state. ,− …”

“…That can be beneficial in some cases, by inducing cooperative spin transitions showing significant thermal hysteresis. − Many SCO-active compounds whose high-spin structures lie inside the pale gray region of Figure fall into that category. However, as ϕ and θ deviate more strongly from the regular geometries preferred by the low-spin complexes, a material is more likely to be kinetically trapped in its high-spin state upon cooling. ,, Over half of the high-spin [Fe­(bpp) 2 ] 2+ derivatives that have been crystallographically characterized to date fall into this category.…”

Detecting Fe(II) Spin-Crossover by Modulation of Appended Eu(III) Luminescence in a Single Molecule

“…In the solid state, intermolecular interactions prevent simple molecular-based rationalization, and complicated multivariate analyses are required to partially analyze the crucial influence of long-range effects resulting from crystal packing . Both [LaFe­( L2 ) 3 ]­(CF 3 SO 3 ) 5 ·1.45H 2 O (Δ H SCO = 13.4(5) kJ·mol –1 , Δ S SCO = 33.0(1) J·mol –1 ·K –1 , T 1/2 = 406(2) K, cooperativity index γ = 3.76(1) kJ·mol –1 ) and [EuFe­( L2 ) 3 ]­(CF 3 SO 3 ) 5 ·1.85H 2 O (Δ H SCO = 23.2(2) kJ·mol –1 , Δ S SCO = 54.4(4) J·mol –1 ·K –1 , T 1/2 = 427(4) K, cooperativity index γ = 2.99(1) kJ·mol –1 ) exhibit spin crossover transitions with transition temperatures T 1/2 larger than those found in solution (Table A6-1 in Appendix 6).…”

“…1,37 In the solid state, intermolecular interactions prevent simple molecular-based rationalization, and complicated multivariate analyses are required to partially analyze the crucial influence of long-range effects resulting from crystal packing. 60 Both [LaFe(L2) 3 ](CF 3 SO 3 ) 5 •1.45H 2 O (ΔH SCO = 13.4(5) kJ•mol −1 , ΔS SCO = 33.0(1) J…”

The effect of inert dopant ions on spin-crossover materials is not simply controlled by chemical pressure

“…9 describes the coupling between the molecular geometry rearrangement and the lattice energy change during SCO in terpyridine embrace crystals. 95…”