Attenuated Total Reflection Infrared Spectra of artificially-prepared gasoline blends have been recorded using the Far-Infrared Beamline at Canadian Light Source in the 600-1200 cm⁻¹region. The CLS Far-infrared Beamline is a synchrotron facility equipped with a high-resolution FT-IR spectrometer and an attenuated total reflection instrument capable of offering a very stable bright light sources and spectral high resolution. The present vibrational spectra display multiple, but distinct, vibrational signatures of ethanol,isopropanol,and hydrocarbon. The analysis of OH bend, C-C and CO stretches by fitting the observed vibrational spectra to a Voigt profile allowed the determination of vibrational centers. For both gasoline blends, we noted significant vibrational shifts and attribute these to changes in force constants as a result of small weak interactions between hydrocarbons and polar component of gasoline blend.

Conformational interconversion is a key aspect of such processes as protein folding, enzyme action via the induced fit mechanism, or the action of molecular motors. Although studies of the dynamics of interconversion exist, they are mostly limited to pump-probe spectroscopy involving electronic excitations, whereas the simplest of these interconversions take place on the ground state potential energy surface. Ortho- and meta-substituted phenols are simple model systems exhibiting syn-anti isomerism, with the two isomers differing by the orientation of the hydroxyl group either towards or away from the heteroatom substituent. The isomerisation reactions between syn- and anti- conformers are characterized by relatively low energy barriers and could potentially be driven using resonant IR vibrational excitation provided by a free electron laser, opening the potential to study interconversion dynamics on the ground state PES. r0pt Figure As a first step we have obtained isomer-specific IR spectra of 3-fluorophenol and 3-chlorophenol by means of IR-UV depletion spectroscopy. Each of these exhibit torsional –OH vibrational bands in the 250-350 cm⁻¹region, with isomer-specific frequencies observed for 3-fluorophenol (as shown in the figure). We subsequently probe the UV spectral response of these molecules following IR excitation of selected bands, employing an IR-UV double resonance scheme. We will present the results of these experiments aimed at understanding vibrational energy coupling in small aromatic systems, as well as discuss the potential for observing direct population transfer between syn- and anti-isomers.

Catalysis represents the key of our modern chemical industry, is essential to reduce waste and air pollution, and plays an important role for solar energy storage as well as electrochemical energy conversion. To direct the optimization of heterogeneous and homogeneous catalysts and to develop new tailor-made catalytic materials a fundamental understanding of the catalytic reactions is indispensable. However, industrial catalysts are typically very complex systems often comprising multiple (nano)materials which render a detailed investigation of the catalytic processes on an atomic and molecular level difficult. To nevertheless gain an essential understanding of catalytic processes, we utilize small (sub)nanometer sized metal, metal-oxide, and metal-sulfur clusters as gas phase model systems. An important aspect that supports the feasibility of such very small isolated systems as catalytic model systems is the fact that catalysis is a local effect and thus generally very restricted to an Ångstrom size atomic area, the so called catalytically active center. These catalytically active centers are typically characterized by unsaturated bonds, like kinks, steps, defects, or very small particles in the sub-nanometer size range and can, thus, be very well modeled by isolated gas phase particles of appropriate size, charge, and material composition. In this talk I will demonstrate the power of gas-phase ion trap reactivity studies in combination with infrared multiple-photon dissociation (IR-MPD) spectroscopy and first-principles calculations to provide a molecular level understanding of fundamental catalytic processes. Particular focus will be on recent spectroscopic studies performed at the free-electron laser facility FELIX (Radboud University Nijmegen, The Netherlands) which are essential for understanding the catalytically active centers of heterogeneous catalysts, biocatalysts, as well as materials of astrochemical relevance.

To achieve a better understanding of strong-field dynamics, the role of Coulomb-potential of the parent ion must be taken into consideration. Several theoretical studies have investigated the effect of coulomb on CEP dependence strong field ionization. However, there are still limited experimental studies on the impact of coulomb potential on the CEP dependent momentum distributions of the photoelectrons. In this work, we experimentally investigated the effect of the long-range and short-range Coulomb potential effect on the phase dependent momentum distributions of photoelectrons by subjecting different gases to the same laser conditions using phase-resolved coincidence imaging technique. The study was performed using both linear and circular polarized light. Our experimental results show that the CEPs at which the low energy electrons have the highest asymmetry is strongly influenced by the ionization potentials but not the electronic structures. This suggests that the long-range potentials are at play. On the contrary, in the case of high-energy electrons, the CEP dependent measurement is mainly governed by the short-range coulomb potential and thus sensitive to the electronic structure of the gas being ionized. These results show that the CEP dependent momentum distributions can be a sensitive probe of the Coulomb potentials.

r0pt Figure Large amounts of methane are present in natural gas, but its great stability hinders wide-spread utilization. Conversion of methane requires a suitable, often transition metal-based catalyst. However, the reaction mechanism is often only poorly understood. To get insight in fundamental chemical interactions at the highest level of detail, we study the interaction between isolated metal ions and methane. For this, we generate metal ions using laser vaporization and react them with methane in a radio-frequency ion trap. After the reaction we analyze the formed products via a combination of mass spectrometry and IR spectroscopy using the Free Electron Laser for IntraCavity Experiments FELICE. We elucidate product structures and reconstruct the reaction pathway by comparison with Density Functional Theory calculations. In this contribution we focus on methane activation by and ions. Previously, it was shown that ions can activate methane to form . Here, we show how the subsequent reaction with more methane molecules leads to dehydrogenation and C–C coupling to form ethene on both and ions.

r0pt Figure Some Ti-based metal organic frameworks (MOFs) have demonstrated photocatalytic properties. MIL125-NH₂ is a well-studied Ti-based MOF consisting of titanium-oxo clusters connected via amino terephthalic acid linkers. This structure possesses a stable, long-lived charge separated excited state in which, upon photoexcitation, an electron migrates from a linker to the metal cluster. The band structure of this framework can be modified through the replacement of Ti metal sites with d block transition metals via a direct synthesis pathway. However, further research is required on the underlying electronic structure and excited state behavior of the modified framework. Fundamental steady state and time resolved X-ray spectroscopy experiments have been carried out in order to determine the effects of heterometal doping concentration on the charge separation lifetime and the electronic environment of MIL125-NH₂. Fe K-edge X-ray transient absorption (XTA) measurements have been conducted, which show that doped MIL125-NH2 has a long-lived excited state lifetime component of over 20 microseconds, due to iron trap sites on the metal ring. The long-lived charge separation excited state is seen even in higher doping levels, as the framework inhibits charge recombination. Ti K-β resonant x-ray emission spectroscopy (RXES) measurements show a shift in pre-edge resonant features towards lower emission energy, with the inclusion of iron heterometals. Localized d transitions on the Ti seem to be less intense with the addition of Fe into the MOF structure.

Enzyme reactivity is often enhanced by changes in oxidation state, spin state, and metal-ligand covalency of associated metallocofactors. The development of spectroscopic methods for studying these processes coincidentally with structural rearrangements is essential for elucidating metalloenzyme mechanisms. Herein, we demonstrate the feasibility of collecting X-ray emission spectra of metalloenzyme crystals at a third-generation synchrotron source. In particular, we report the development of a von Hamos spectrometer for the collection of Fe Kβ emission optimized for analysis of dilute biological samples. We further showcase the application of this high-resolution, "DIY" mini-spectrometer in crystals of the immunosuppressive heme-dependent enzyme indoleamine 2,3-dioxygenase (IDO). Spectra obtained from reference compounds were compared to catalytically-relevant states of IDO via integrated absolute difference analysis to determine their spin numbers. Complementary density functional calculations assessing covalency support our spectroscopic analysis and identify active site conformations that correlate to high- and low-spin systems. These experiments validate the suitability of an X-ray emission approach for determining spin states of previously uncharacterized metalloenzyme reaction intermediates.

Transition-metal oxides, especially nickel, copper and cobalt oxides, are potential candidates for robust water splitting electrocatalysts as they are valence-tunable, earth-abundant, cost-efficient and stock-available. Bifunctional polyoxometalate electrocatalysts are becoming more common because of their low production cost and enhanced. water splitting activity as compared to noble metals. The water electrolysis can be divided into two half reactions: hydrogen evolution reaction (HER) occurring at the cathode, while the anodic process involves the oxygen evolution reaction (OER). Both half-reactions involve proton-coupled multi-electron transfers, varied by the pH and other reaction conditions. The general mechanism of HER involves an electrochemical hydrogen adsorption step followed by an electrochemical desorption or recombination reaction. In the case of OERs, it involves the formation of adsorbed OH* on the catalyst surface with the subsequent transformation to OOH* and the eventual release of O2. We (Streb group) recently reported cobalt tungstate bifunctional catalyst deposited on copper foam, showing high water electrolysis activity. The composite catalyst showed sustained OER and HER activity in 0.1 M aqueous KOH over prolonged periods (t more than 10 h) at low overpotentials (OER: 300 mV; HER: 100 mV). But studies evaluating the mechanistic understanding of each step in water splitting electrolysis, structural changes and true active sites during HERs and OERs at high pH values still remain ambiguous. XAS was used to study the catalytic intermediates represents a novel approach to probe the catalytic intermediates and to understand the mechanism of a catalytic process which is of outmost importance for designing new and more efficient systems.

l0pt Figure Metal-organic framework (MOF) materials are porous coordination polymers that have gained interest due to the tunability of the guest and host structures. This tunability can be particularly useful in electroconductivity applications yet has been challenging to implement due to their intrinsic insulating nature. Exploring ways to tune the electronic structure to promote electron migration is a key component in furthering research for applications that rely on conductivity such as electrocatalysis and sensing. Introduction of redox active guest species into effectively insulating MOF structures is one strategy being explored to impart electrical conductivity. This talk will focus on one particular host-guest system: a Cu3(BTC)2 MOF (; BTC=benzene 1,3,5-triboxylic acid) infiltrated with redox active 7,7,8,8-tetracyanoquinododimethane (TCNQ) guest molecules. It has been reported previously that the introduction of TCNQ into the pores Cu3(BTC)2 leads to an increase in conductivity. A key component of understanding this system is the interaction occurring between the copper sites of the framework and TCNQ guest molecules. A fundamental study using vibrational and X-ray spectroscopy were used to further understand this interaction. Copper K-alpha, resonant X-ray emission spectroscopy (RXES) was used to specifically probe the Cu interaction with this redox active guest. HERFD XANES spectra extracted from the 2D RXES planes reveal subtle changes of the pre-edge features and additional edge features corresponding the pi-backbonding of the TCNQ cyano groups to the Cu sites in the framework. Cu K-edge data are supplemented by TD-DFT calculations to determine the orbital contributions to different edge features and therefore the nature of this host-guest interaction on a molecular level.