Light-induced excited spin state trapping in a transition-metal complex: The hexa-1-propyltetrazole-iron (II) tetrafluoroborate spin-crossover system

Decurtins, Silvio; Gütlich, Philipp; Köhler, C.P.; Spiering, H.; Hauser, Andreas

doi:10.1016/0009-2614(84)80403-0

Cited by 1,047 publications

(671 citation statements)

References 14 publications

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“…Photogeneration of the metastable HS state at low temperatures, the so-called Light-Induced Excited Spin-State Trapping (LIESST) experiment, [15] was carried out on a microcrystalline sample (0.46 mg). The results are displayed in Figure 1.…”

Section: Resultsmentioning

confidence: 99%

Thermal‐ and Photoinduced Spin‐State Switching in an Unprecedented Three‐Dimensional Bimetallic Coordination Polymer

Niel

Thompson

Goeta

et al. 2005

Chemistry A European J

131

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The compound {Fe(pmd)[Ag(CN)2][Ag2(CN)3]} (pmd=pyrimidine) was synthesized and characterized. Magnetic, calorimetric and single crystal visible spectroscopic studies demonstrate the occurrence of a two-step high-spin (HS) low-spin (LS) transition. The critical temperatures are Tc1=185 and Tc2=148 K. Each step involves 50 % of the iron centers, with the low-temperature step showing a hysteresis of 2.5 K. The enthalpy and entropy variations associated with the two steps are H1=3.6±0.4 kJ mol-1 and S1=19.5±3 J K-1 mol-1; H2=4.8±0.4 kJ mol-1 and S2=33.5±3 J K-1 mol-1. Photomagnetic and visible spectroscopy experiments show that below 50 K, where the LS state is the thermodynamically stable state, the compound can be switched quantitatively to the HS state using green-red light (550-650 nm). HS-to-LS relaxation experiments in the dark at temperatures between 15 and 55 K show that the relaxation takes place via a two-step cooperative process, which was analyzed in the context of the mean field theory. The crystal structure has been studied at 290, 220, 170, 90 and 30 K together with 30 K after irradiation. The compound adopts monoclinic symmetry (P21/c, Z=16) at all temperatures. There are five [FeN6] pseudo-octahedral sites linked by pmd, [Ag(CN)2]- and [Ag2(CN)3]- bridging ligands to form an unprecedented three-dimensional (6,6) topology. The structural analysis allows for an understanding of the microscopic mechanism of the two-step behavior of the thermally induced spin transition as well as the corresponding relaxation of the photoexcited compound based on the individual changes of the five sites. Synergy between metallophilic interactions and the spin transition is also shown by the variation of the AgAg distances. Correlations between the variation of the unit-cell volume and the change of AgAg interactions within each step with the asymmetric change of the anomalous heat capacity have also been inferred

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Section: Resultsmentioning

confidence: 99%

Thermal‐ and Photoinduced Spin‐State Switching in an Unprecedented Three‐Dimensional Bimetallic Coordination Polymer

Niel

Thompson

Goeta

et al. 2005

Chemistry A European J

131

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“…52,53 The LIESST effect involves "trapping" the high-spin state of a solid SCO compound by lowering its temperature and irradiating it with an incoherent light source to yield an almost complete conversion of the solid sample to its high-spin form. In this study, we impulsively photoinduce a spin crossover transition in an Fe II compound in solution and then directly probe the electronic and structural properties of the transient population of the high-spin 5 T 2 state at ambient temperature.…”

Section: X-ray Absorption Spectroscopy Of the Ground-statementioning

confidence: 99%

Picosecond X-ray Absorption Spectroscopy of a Photoinduced Iron(II) Spin Crossover Reaction in Solution

et al. 2005

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In this study, we perform steady-state and time-resolved X-ray absorption spectroscopy (XAS) on the iron K-edge of [Fe(tren(py) 3 )](PF 6 ) 2 dissolved in acetonitrile solution. Static XAS measurements on the low-spin parent compound and its high-spin analogue, 3 )](PF 6 ) 2 , reveal distinct spectroscopic signatures for the two spin states in the X-ray absorption near-edge structure (XANES) and in the X-ray absorption fine structure (EXAFS). For the time-resolved studies, 100 fs, 400 nm pump pulses initiate a charge-transfer transition in the low-spin complex. The subsequent electronic and geometric changes associated with the formation of the high-spin excited state are probed with 70 ps, 7.1 keV, tunable X-ray pulses derived from the Advanced Light Source (ALS). Modeling of the transient XAS data reveals that the average iron-nitrogen (Fe-N) bond is lengthened by 0.21 ( 0.03 Å in the high-spin excited state relative to the ground state within 70 ps. This structural modification causes a change in the metal-ligand interactions as reflected by the altered density of states of the unoccupied metal orbitals. Our results constitute the first direct measurements of the dynamic atomic and electronic structural rearrangements occurring during a photoinduced Fe II spin crossover reaction in solution via picosecond X-ray absorption spectroscopy.

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“…16 The transformation can also be effected upon photoexcitation as demonstrated by the so-called LIESST effect (Light-Induced Excited SpinState Trapping) first reported by Decurtins and co-wrokers. 17 Interest in these widely studied compounds stems from the profound difference in optical, magnetic, and geometric properties endemic to the two accessible spin states, suggesting possible applications in magneto-optics among others. 18,19 Of fundamental scientific interest is the complex coupling of electronic, nuclear and magnetic (spin & orbital) degrees of freedom.…”

Section: Introductionmentioning

confidence: 99%

Photo-Induced Spin-State Conversion in Solvated Transition Metal Complexes Probed via Time-Resolved Soft X-ray Spectroscopy

et al. 2010

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Solution-phase photo-induced low-spin to high-spin conversion in the Fe II polypyridyl complex [Fe(tren(py) 3 )] 2+ (where tren(py) 3 is tris(2-pyridylmethylimino-ethyl)amine) has been studied via picosecond soft x-ray spectroscopy. Following 1 A 1 → 1 MLCT (metal-to-ligand charge transfer) excitation at 560 nm, changes in the iron L 2 and L 3 edges were observed concomitant with formation of the transient high-spin 5 T 2 state. Charge-transfer multiplet calculations coupled with data acquired on low-spin and high-spin model complexes revealed a reduction in ligand field splitting of ~1 eV in the high-spin state relative to the singlet ground state. A significant reduction in orbital overlap between the central Fe-3d and the ligand N-2p orbitals was directly observed, consistent with the expected ca. 0.2 Å increase in Fe-N bond length upon formation of the high-spin state. The overall occupancy of the Fe 3d-orbitals remains constant upon spin-crossover, suggesting that the reduction in σ-donation is compensated by significant attenuation of π-back-bonding in the metal-ligand interactions. These results demonstrate the feasibility and unique potential of time-resolved soft x-ray absorption spectroscopy to study ultrafast reactions in the liquid phase by directly probing the valence orbitals of first-row metals as well as lighter elements during the course of photochemical transformations.

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Light-induced excited spin state trapping in a transition-metal complex: The hexa-1-propyltetrazole-iron (II) tetrafluoroborate spin-crossover system

Cited by 1,047 publications

References 14 publications

Thermal‐ and Photoinduced Spin‐State Switching in an Unprecedented Three‐Dimensional Bimetallic Coordination Polymer

Thermal‐ and Photoinduced Spin‐State Switching in an Unprecedented Three‐Dimensional Bimetallic Coordination Polymer

Picosecond X-ray Absorption Spectroscopy of a Photoinduced Iron(II) Spin Crossover Reaction in Solution

Photo-Induced Spin-State Conversion in Solvated Transition Metal Complexes Probed via Time-Resolved Soft X-ray Spectroscopy

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