Determination of the molecular structure of the short-lived light-induced high-spin state in the spin-crossover compound [Fe(6-mepy)3tren](PF6)

Abstract

In the spin-crossover compound 3 tren](PF 6 ) 2 , (6-mepy) 3 tren = tris{4-[(6-methyl)-2-pyridyl]-3-aza-butenyl}amine, the high-spin state can be populated as a metastable state below the thermal transition temperature via irradiation into the metal to the ligand charge-transfer absorption band of the low-spin species. At 10 K, the lifetime of this metastable state is only 1 s. Despite this, it is possible to determine an accurate excited state structure by following the evolution of relevant structural parameters by synchrotron x-ray diffraction under continuous irradiation with increasing intensity. The difference in metal-ligand bond length between the high-spin and the low-spin states is found to be 0.192Å, obtained from an analysis of the experimental data using the mean-field approximation to model cooperative effects.

FeII Complexes with Triple N1,N2‐Triazole Bridge Schiff Base Ligand: Antiferromagnetic Dimer vs. Spin Conversion Trimer

“…The terminal average Fe–N bond lengths 2.139(1) Å ( C1 ), and 2.144(1) Å ( C2 ) are shorter than the central average Fe–N bond lengths 2.197(1) Å ( C1 ) and 2.191(1) Å ( C2 ). (Table S3) In both cases, the average bond length makes the Fe centers sitting well in the range expected for high spin state value at 173 K, which is further confirmed by magnetic measurement. (See below) The NCS – anions in C1 are non‐linear with the N–C–S fragment showing an angle around 175°; the angle at the N‐atom coordinating to the iron atoms, Fe ··· N–C, is split into two groups with the angle being around 140° and 175°.…”

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

“…The terminal average Fe−N bond length of 2.113(3) Å is shorter than the central average Fe−N bond length of 2.159(3) Å (Table S3). In both cases, the bond distance confirms the Fe centers being in the high-spin state at 173 K [37], which is further confirmed by magnetic measurements (see below). The NCS − anions are almost linear with the N-C-S angle around 178 • ; the angle of coordination to iron Fe-N-C is split into two groups with the angle being around 160 • and 175 • (Table S3).…”

Structural Investigation of the High Spin→Low Spin Relaxation Dynamics of the Porous Coordination Network [Fe(pz)Pt(CN)4]⋅2.6 H2O

“…10 Thus, photoinduced HS structures have been determined at cryogenic temperatures by using single‐crystal X‐ray diffraction (XRD) studies of a number of compounds for which the HS→LS relaxation dynamics are much slower than the measurement timescale 11. More recently, an investigation of steady‐state structures under continuous irradiation has been used to extrapolate the photoinduced HS structure of a compound for which the HS lifetime at 10 K is only a few seconds 12. Depending on the compound, the photoinduced HS structure can be similar or completely different from the thermally populated structure.…”