Photolysis of a High‐Spin Azidoiron(III) Complex Studied by Time‐Resolved Fourier‐Transform Infrared Spectroscopy

Torres-Alacan, Joel; Vöhringer, Peter

doi:10.1002/chem.201700960

Cited by 17 publications

(14 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Initially, most iron nitrides were successfully prepared in frozen solutions, which indicated that a solid matrix and low temperatures were required for their generation . However, ultrafast experiments have recently shown the formation of iron nitrides at room temperature …”

Section: Figurementioning

confidence: 99%

“…[19,20] However,u ltrafast experiments have recently shown the formation of iron nitrides at room temperature. [21][22][23] Herein, we report the photodissociation of iron(III) azides studied at the molecular level by ion spectroscopy using different temperatures (3-310 K). [24][25][26][27] Photo-dissociation of mass-selected iron azide complexes 1 [28] in the visible range resulted in photoreduction associated with N 3 C elimination or photooxidation, forming the desired iron-(V) nitride complex 3,concomitantly with the elimination of N 2 (Scheme 1).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Spin‐State‐Controlled Photodissociation of Iron(III) Azide to an Iron(V) Nitride Complex

et al. 2017

View full text Add to dashboard Cite

The generation of iron(V) nitride complexes, which are targets of biomimetic chemistry, is reported. Temperature-dependent ion spectroscopy shows that this reaction is governed by the spin-state population of their iron(III) azide precursors and can be tuned by temperature. The complex [(MePy TACN)Fe(N )] (MePy TACN=N-methyl-N,N-bis(2-picolyl)-1,4,7-triazacyclononane) exists as a mixture of sextet and doublet spin states at 300 K, whereas only the doublet state is populated at 3 K. Photofragmentation of the sextet state complex leads to the reduction of the iron center. The doublet state complex photodissociates to the desired iron(V) nitride complex. To generalize these findings, we show results for complexes with cyclam-based ligands.

show abstract

Section: Figurementioning

confidence: 99%

mentioning

confidence: 99%

Spin‐State‐Controlled Photodissociation of Iron(III) Azide to an Iron(V) Nitride Complex

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Whereas the ensuing chemical processes of such nascent products are understood quite straightforwardly in terms of first-order, pseudo-first-order, or second-order kinetics depending on the molecularity and the reaction conditions, ,− the primary elementary steps are often more difficult to quantify. This is because such processes generally occur on very short time scales (from a few tens of femtoseconds to hundreds of picoseconds), and their experimental observation necessitates sophisticated ultrafast laser spectroscopies.…”

Section: Introductionmentioning

confidence: 99%

Vibrational Relaxation Dynamics of an Azido–Cobalt(II) Complex from Femtosecond UV-Pump/MIR-Probe Spectroscopy and Model Simulations with Ab Initio Anharmonic Couplings

et al. 2020

Self Cite

View full text Add to dashboard Cite

Vibrational energy relaxation is of critical importance for the lightcontrolled reactivity of transition-metal complexes. In time-resolved optical spectroscopies, it gives rise to pronounced spectral redistributions with complex band shifts and thus to nonexponential kinetics, all of which are very difficult to quantify. Here we study the vibrational relaxation dynamics of a pentacoordinated azido−cobalt(II) complex in liquid solution following its ultrafast charge-transfer excitation in the near-ultraviolet (UV). The complex is photochemically remarkably stable and returns within the experimental time resolution back to its quartet electronic ground state via internal conversion. The nonadiabatic transition effectively instantaneously converts the entire photon energy into kinetic energy of the vibrational degrees of freedom. The ensuing relaxation dynamics of the vibrationally highly excited complex are monitored as a function of time using femtosecond mid-infrared (MIR) spectroscopy in the antisymmetric stretching region of the azido ligand and occur on a time scale of a few tens of picoseconds. The dynamic evolution of the MIR spectrum due to vibrational cooling of the complex can be understood quantitatively within the framework of an anharmonic coupling model, which relies on an ab initio intramolecular cubic/quartic force field from density functional theory combined with second-order vibrational perturbation theory. The simulations suggest that the primary internal conversion preferentially dumps the excess energy into the low-frequency bending modes of the azido ligand, whereas its high-frequency stretching modes are barely affected by the initial nonadiabatic transition. Surprisingly, the two bending vibrations appear to relax independently of one another, each with its own characteristic cooling time.

show abstract

“…We have recently undertaken a significant research effort aimed at unraveling the photochemical and photophysical primary processes leading to the formation of high-valent nitridoiron(V) species and to study in detail their chemical reactivities in liquid solution under ambient conditions using a combination of ultrafast mid-infrared (MIR) spectroscopy and time-resolved Fourier-transform infrared (FTIR) spectroscopy following flash photolysis. − It was found that the desired dinitrogen cleavage and photooxidation of the iron center has to compete with the heterolytic cleavage of azide anions on the one hand and the homolytic loss of azide radicals and photoreduction of the metal on the other. An increase of the photolysis photon energy leads to a rising quantum yield for photooxidation.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Dynamics of a Diazidocobalt(III) Complex Studied by Femtosecond UV-Pump/IR-to-Vis-Probe Spectroscopy

et al. 2019

Self Cite

View full text Add to dashboard Cite

The photochemistry of the cationic diazidocobalt(III) complex, trans-[Co(cyclam)(N3)2]+, following its ligand-to-metal charge transfer (LMCT) excitation is studied in liquid dimethyl sulfoxide (DMSO) solution using femtosecond spectroscopy with detection in a very broad spectral region covering the near-ultraviolet (near-UV) all the way to the mid-infrared (MIR), thereby enabling a combined probing of electronic and vibrational degrees of freedom of the dynamically evolving system. The initially prepared singlet LMCT-state decays, via the metal-centered singlet excited state, 1MC(1Eg), into the triplet ground state, 3MC (3Eg/3A1g), on a time scale shorter than 25 ps. During this time period, the vibrational spectrum demonstrates uniquely that the nature of the complex changes from a monoazidocobalt(II) species bearing a neutral azide radical ligand immediately after photon absorption to a metal-centered open-shell diazidocobalt(III) species. At the same time, the 3MC state is characterized by a very strong absorption band centered at 710 nm, which can be assigned to a transition to the triplet LMCT state. The 1LMCT lifetime is about 2 ps, whereas that of the excited state, 1MC, is defined by the primary intersystem crossing time of 6 ps. The ensuing intersystem recrossing from 3MC to the parent’s singlet ground state, 1A1g, occurs with a rate of 1/(110 ps). The mid-infrared pump–probe spectrum after 1 ns, gives evidence for a heterolytic Co–N bond fission with a quantum yield of ∼5%, leading to free azide anions and the monoazido species, trans-[Co(cyclam)(N3)(OSMe2)]+, featuring an oxygen-bound DMSO ligand in its coordination sphere.

show abstract

Photolysis of a High‐Spin Azidoiron(III) Complex Studied by Time‐Resolved Fourier‐Transform Infrared Spectroscopy

Cited by 17 publications

References 41 publications

Spin‐State‐Controlled Photodissociation of Iron(III) Azide to an Iron(V) Nitride Complex

Spin‐State‐Controlled Photodissociation of Iron(III) Azide to an Iron(V) Nitride Complex

Vibrational Relaxation Dynamics of an Azido–Cobalt(II) Complex from Femtosecond UV-Pump/MIR-Probe Spectroscopy and Model Simulations with Ab Initio Anharmonic Couplings

Photoinduced Dynamics of a Diazidocobalt(III) Complex Studied by Femtosecond UV-Pump/IR-to-Vis-Probe Spectroscopy

Contact Info

Product

Resources

About