Ultrafast "end-on"-to-"side-on" binding-mode isomerization of an iron-carbon dioxide complex.

Carbon dioxide (CO) binding by transition metals is a captivating phenomenon with a tremendous impact in environmental science and technology, most notably, for establishing circular economies based on greenhouse gas emissions. The molecular and electronic structures of coordination compounds containing CO can be studied in great detail using photochemical precursors bearing the photolabile oxalato-ligand. Here, we study the photoinduced elementary dynamics of the ferric complex, [Fe(cyclam)(CO)], in dimethyl sulfoxide solution using femtosecond mid-infrared spectroscopy following oxalate-to-iron charge transfer excitation with 266 nm pulses.

Spin-Controlled Binding of Carbon Dioxide by an Iron Center: Insights from Ultrafast Mid-Infrared Spectroscopy.

The influence of the spin on the mode of binding between carbon dioxide (CO ) and a transition-metal (TM) center is an entirely open question. Herein, we use an iron(III) oxalato complex with nearly vanishing doublet-sextet gap, and its ultrafast photolysis, to generate TM-CO bonding patterns and determine their structure in situ by femtosecond mid-infrared spectroscopy. The formation of the nascent TM-CO species according to [L Fe (C O )] + hν → [L Fe(CO )] + CO , with L =cyclam, is evidenced by the coincident appearance of the characteristic asymmetric stretching absorption of the CO -ligand between 1600 cm and 1800 cm and that of the free CO -co-fragment near 2337 cm .

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

Vibrational energy relaxation is of critical importance for the light-controlled 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).

Molecular and electronic structure of an azidocobalt(iii) complex derived from X-ray crystallography, linear spectroscopy and quantum chemical calculations.

The photochemistry of transition-metal azides is remarkably complex and can involve multiple competing pathways leading to different fragmentation patterns. Therefore, an in-depth study of such rich photochemistry requires a thorough prior understanding of the molecular and electronic structures of these complexes. To this end, stationary (i.

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

The photochemistry of the cationic diazidocobalt(III) complex, -[Co(cyclam)(N)], 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, MC(E), into the triplet ground state, MC (E/A), 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.

Femtosecond infrared spectroscopy reveals the primary events of the ferrioxalate actinometer.

Chemical actinometry is an indispensable analytical tool in preparative photochemistry that allows for a precise measurement of radiant fluxes inside photoreactors. An actinometer thus enables an absolute determination of the quantum yield of a photochemical reaction of interest. The "gold standard" of chemical actinometry in liquid systems is the Hatchard-Parker actinometer, i.

An Iron Complex with a Bent, O-Coordinated CO Ligand Discovered by Femtosecond Mid-Infrared Spectroscopy.

The activation of carbon dioxide by transition metals is widely recognized as a key step for utilizing this greenhouse gas as a renewable feedstock for the sustainable production of fine chemicals. However, the dynamics of CO binding and unbinding to and from the ligand sphere of a metal have never been observed in the time domain. The ferrioxalate anion is used in aqueous solution as a unique model system for these dynamics and femtosecond UV-pump mid-infrared-probe spectroscopy is applied to explore its photoinduced primary processes in a time-resolved fashion.

Photochemical Kinetics of a Phosphine Oxide Free Radical Initiator from Femtosecond UV-Pump/Mid-IR-Probe Spectroscopy.

Femtosecond UV-pump/mid-infrared-probe spectroscopy was used to explore in detail the primary photochemical events of the free radical initiator, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, in liquid dichloromethane solution at room temperature. Following electronic excitation of its lowest excited singlet state, S, the radical initiator undergoes an intersystem crossing to the triplet ground state, T, with a time constant of 135 ps. A subsequent α-cleavage occurs from the triplet state with a time constant of 15 ps and yields a trimethylbenzoyl radical together with a diphenylphosphinoyl radical.