Hexafluorophosphate-Triggered Hydrogen Isotope Exchange (HIE) in Fluorinated Environments: A Platform for the Deuteration of Aromatic Compounds via Strong Bond Activation.

There is a perpetual need for efficient and mild methods to integrate deuterium atoms into carbon frameworks through late-stage modifications. We have developed a simple and highly effective synthetic route for hydrogen isotope exchange (HIE) in aromatic compounds under ambient conditions. This method utilizes catalytic amounts of hexafluorophosphate (PF ) in deuterated 1,1,1,3,3,3-hexafluoroisopropanol (HFIP-d) and DO.

Direct evidence for ligand-enhanced activity of Cu(i) sites.

Little is known about the strong mediating effect of the ligand sphere and the coordination geometry on the strength and isotopologue selectivity of hydrogen adsorption on the undercoordinated copper(i) site. Here, we explore this effect using gas-phase complexes Cu(HO)(H) (with ≤ 3) as model systems. Cu(HO) attracts dihydrogen (82 kJ mol ) more strongly than bare Cu (64 kJ mol ) does.

Online-Monitoring of the Enantiomeric Ratio in Microfluidic Chip Reactors Using Chiral Selector Ion Vibrational Spectroscopy.

A novel experimental approach for the rapid online monitoring of the enantiomeric ratio of chiral analytes in solution is presented. The charged analyte is transferred to the gas phase by electrospray. Diastereomeric complexes are formed with a volatile chiral selector in a buffer-gas-filled ion guide held at room temperature, mass-selected, and subsequently spectrally differentiated by cryogenic ion trap vibrational spectroscopy.

Vibrational wave-packet dynamics of the silver pentamer probed by femtosecond NeNePo spectroscopy.

Vibrational wave-packet dynamics on the ground electronic state of the neutral silver pentamer (Ag) are studied by femtosecond (fs) pump-probe spectroscopy using the 'negative ion - to neutral - to positive ion' (NeNePo) excitation scheme. A vibrational wave packet is prepared on the A state of Ag photodetachment of mass-selected, cryogenically cooled Ag anions using a fs pump pulse. The temporal evolution of the vibrational wave packet is then probed by an ultrafast probe pulse resonant multiphoton ionization to Ag.

Binding Properties of Small Electrophilic Anions [B X ] and [B X ] (X=Cl, Br, I): Activation of Small Molecules Based on π-Backbonding.

Superelectrophilic anions constitute a special class of molecular anions that show strong binding of weak nucleophiles despite their negative charge. In this study, the binding characteristics of smaller gaseous electrophilic anions of the types [B X ] and [B X ] (with X=Cl, Br, I) were computationally and experimentally investigated and compared to those of the larger analogues [B X ] . The positive charge of vacant boron increases from [B X ] via [B X ] to [B X ] , as evidenced by increasing attachment enthalpies towards typical σ-donor molecules (noble gases, H O).

Nuclear quantum dynamics on the ground electronic state of neutral silver dimer AgAg probed by femtosecond NeNePo spectroscopy.

The nuclear quantum dynamics on the ground electronic state of the neutral silver dimer AgAg are studied by femtosecond (fs) pump-probe spectroscopy using the 'negative ion - to neutral - to positive ion' (NeNePo) excitation scheme. A vibrational wave packet is prepared on the XΣ+g state of Ag photodetachment of mass-selected, cryogenically cooled Ag using a first ultrafast pump laser pulse. The temporal evolution of the wave packet is then probed by an ultrafast probe pulse resonant multiphoton ionization to Ag.

Vibrational spectroscopy of Cu(H): about anharmonicity and fluxionality.

The vibrational spectra of the copper(I) cation-dihydrogen complexes Cu(H), Cu(D) and Cu(D)H are studied using cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations. The infrared photodissociation (IRPD) spectra (2500-7300 cm) are assigned based on a comparison to IR spectra calculated using vibrational second-order perturbation theory (VPT2). The IRPD spectra exhibit ≈60 cm broad bands that lack rotational resolution, indicative of rather floppy complexes even at an ion trap temperature of 10 K.

Rovibrational investigation of a new high-lying 0 state of Cu by using two-color resonant four-wave-mixing spectroscopy.

A highly excited electronic state of dicopper is observed and characterized for the first time. The [39.6]0 -XΣ (0 ) system is measured at rotational resolution by using degenerate and two-color resonant four-wave-mixing, as well as laser induced fluorescence spectroscopy.

Infrared Spectroscopy and Bonding of the B(NN) and B(NN) Cation Complexes.

The boron-dinitrogen cation complexes B(NN) and B(NN) are produced in the gas phase and are studied by infrared photodissociation spectroscopy in the N-N stretching vibrational frequency region. The geometric and electronic structures are determined by comparison of the experimental spectra with density functional theory calculations. The B(NN) cation is characterized to have a closed-shell singlet ground state with planar symmetry.

Generation and simple characterization of flat, liquid jets.

We present an approach to determine the absolute thickness profile of flat liquid jets, which takes advantage of the information of thin film interference combined with light absorption, both captured in a single microscopic image. The feasibility of the proposed method is demonstrated on our compact experimental setup used to generate micrometer thin, free-flowing liquid jet sheets upon collision of two identical laminar cylindrical jets. Stable operation was achieved over several hours of the flat jet in vacuum (10 mbar), making the system ideally suitable for soft x-ray photon spectroscopy of liquid solutions.

Generation and Identification of the Linear OCBNO and OBNCO Molecules with 24 Valence Electrons.

Two structural isomers containing five second-row element atoms with 24 valence electrons were generated and identified by matrix-isolation IR spectroscopy and quantum chemical calculations. The OCBNO complex, which is produced by the reaction of boron atoms with mixtures of carbon monoxide and nitric oxide in solid neon, rearranges to the more stable OBNCO isomer on UV excitation. Bonding analysis indicates that the OCBNO complex is best described by the bonding interactions between a triplet-state boron cation with an electron configuration of (2s) (2p ) (2p ) and the CO/NO ligands in the triplet state forming two degenerate electron-sharing π bonds and two ligand-to-boron dative σ bonds.

A Homoleptic Beryllium Carbonyl Complex with an End-On and Side-On Bridging Carbonyl Ligand.

Homoleptic dinuclear beryllium carbonyl cation complexes have been produced and characterized in the gas phase. Infrared photodissociation spectroscopic and theoretical results confirm that Be (CO) is a coordination saturated complex that can be assigned to a mixture of two almost isoenergetic structural isomers. Besides a beryllium-beryllium single-bonded (OC) Be-Be(CO) isomer, another structure involving an unusual end-on and side-on bridging carbonyl ligand with very low carbonyl stretching frequency is identified.

Filling a Gap: The Coordinatively Saturated Group 4 Carbonyl Complexes TM(CO) (TM=Zr, Hf) and Ti(CO).

Homoleptic Group 4 metal carbonyl cation and neutral complexes were prepared in the gas phase and/or in solid neon matrix. Infrared spectroscopy studies reveal that both zirconium and hafnium form eight-coordinate carbonyl neutral and cation complexes. In contrast, titanium forms only the six-coordinate Ti(CO) and seven-coordinate Ti(CO) .

Octa-coordinated alkaline earth metal-dinitrogen complexes M(N) (M=Ca, Sr, Ba).

We report the isolation and spectroscopic identification of the eight-coordinated alkaline earth metal-dinitrogen complexes M(N) (M=Ca, Sr, Ba) possessing cubic (O) symmetry in a low-temperature neon matrix. The analysis of the electronic structure reveals that the metal-N bonds are mainly due to [M(d)]→(N) π backdonation, which explains the observed large red-shift in N-N stretching frequencies. The adducts M(N) have a triplet (A) electronic ground state and exhibit typical bonding features of transition metal complexes obeying the 18-electron rule.

Octacarbonyl Ion Complexes of Actinides [An(CO) ] (An=Th, U) and the Role of f Orbitals in Metal-Ligand Bonding.

The octacarbonyl cation and anion complexes of actinide metals [An(CO) ] (An=Th, U) are prepared in the gas phase and are studied by mass-selected infrared photodissociation spectroscopy. Both the octacarbonyl cations and anions have been characterized to be saturated coordinated complexes. Quantum chemical calculations by using density functional theory show that the [Th(CO) ] and [Th(CO) ] complexes have a distorted octahedral (D ) equilibrium geometry and a doublet electronic ground state.

Infrared photodissociation spectroscopic studies of ScO(HO)Ar cluster cations: solvation induced reaction of ScO and water.

We investigate the gaseous ScO(H2O)1-3Ar+ cations prepared by laser vaporization coupled with supersonic molecular beam using infrared photodissociation spectroscopy in the O-H stretching region. The cation structures are characterized by comparing the experimentally observed frequencies with the simulated vibration spectra. We reveal that stoichiometric ScO(H2O)Ar+ is intrinsically the hydrated oxide cation expressed as H2O-ScOAr+ hydrate rather than Sc(OH)2Ar+ dihydroxide, although the former is higher in energy by 29.

Infrared photodissociation spectroscopic investigation of TMO(CO) (TM = Sc, Y, La): testing the 18-electron rule.

Gaseous TMO(CO) (TM = Sc, Y, La) complex cations prepared via laser vaporization were mass-selected and studied by infrared photodissociation spectroscopy in the C-O stretching frequency region. The structures and vibrational frequencies were calculated by density functional theory to support and interpret the experimental results. The saturated coordination number of CO ligands for ScO(CO), YO(CO) and LaO(CO) was demonstrated to be six, seven and nine, respectively, namely, the nominal 18-, 20- and 24-electron gaseous cation complexes were synthesized.

Octacarbonyl Anion Complexes of the Late Lanthanides Ln(CO) (Ln=Tm, Yb, Lu) and the 32-Electron Rule.

The lanthanide octacarbonyl anion complexes Ln(CO) (Ln=Tm, Yb, Lu) were produced in the gas phase and detected by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching-frequency region. By comparison of the experimental CO-stretching frequencies with calculated data, which are strongly red-shifted with respect to free CO, the Yb(CO) and Lu(CO) complexes were determined to possess octahedral (O ) symmetry and a doublet X A (Yb) and singlet X A (Lu) electronic ground state, whereas Tm(CO) exhibits a D equilibrium geometry and a triplet X B ground state. The analysis of the electronic structures revealed that the metal-CO attractive forces come mainly from covalent orbital interactions, which are dominated by [Ln(d)]→(CO) π backdonation and [Ln(d)]←(CO) σ donation (contributes ≈77 and 16 % to covalent bonding, respectively).

Boron carbonyl complexes analogous to hydrocarbons.

Recent studies on boron carbonyl complexes show their intriguing structural and bonding properties, enriching our knowledge on main group coordination chemistry. The isolobal relationships between BCO and CH and the more generally applicable CO/H- and B-/C analogies are employed to understand the structure and bonding of boron carbonyl complexes, bridging the boron carbonyl chemistry to the well-known hydrocarbon analogues.

Observation of alkaline earth complexes M(CO) (M = Ca, Sr, or Ba) that mimic transition metals.

The alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) typically engage in chemical bonding as classical main-group elements through their s and p valence orbitals, where is the principal quantum number. Here we report the isolation and spectroscopic characterization of eight-coordinate carbonyl complexes M(CO) (where M = Ca, Sr, or Ba) in a low-temperature neon matrix. Analysis of the electronic structure of these cubic -symmetric complexes reveals that the metal-carbon monoxide (CO) bonds arise mainly from [M(d)] → (CO) π backdonation, which explains the strong observed red shift of the C-O stretching frequencies.

Octacarbonyl Anion Complexes of Group Three Transition Metals [TM(CO) ] (TM=Sc, Y, La) and the 18-Electron Rule.

We report the gas-phase synthesis of stable 20-electron carbonyl anion complexes of group 3 transition metals, TM(CO) (TM=Sc, Y, La), which are studied by mass-selected infrared (IR) photodissociation spectroscopy. The experimentally observed species, which are the first octacarbonyl anionic complexes of a TM, are identified by comparison of the measured and calculated IR spectra. Quantum chemical calculations show that the molecules have a cubic (O ) equilibrium geometry and a singlet ( A ) electronic ground state.

Boron Carbonyl Analogues of Hydrocarbons: An Infrared Photodissociation Spectroscopic Study of B(CO) ( n = 4-6).

The boron carbonyl cluster cations in the form of B(CO) ( n = 4-6) are produced and studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region in the gas phase. Their geometric structures are determined with the aid of density functional theory calculations. The B(CO) cation is characterized to have a D (OC)B═B═B(CO) structure and A electronic ground state with a linear boron skeleton.

Preparation and characterization of chemically bonded argon-boroxol ring cation complexes.

The cation complexes [ArBO], [ArBO], [ArBO] and [ArBO] were prepared a laser vaporization supersonic ion source in the gas phase. Their vibrational spectra were measured mass-selected infrared photodissociation spectroscopy. Spectroscopy combined with quantum chemical calculations revealed that the [ArBO], [ArBO] and [ArBO] cation complexes have planar structures each involving an aromatic boroxol ring and an argon-boron covalent bond.

Infrared spectroscopic and theoretical study of the HCO (n = 2-5) cations.

The carbon chain cations, HCO (n = 2-5), are produced via pulsed laser vaporization of a graphite target in supersonic expansions containing carbon monoxide and hydrogen. The infrared spectra are measured via mass-selected infrared photodissociation spectroscopy of the CO "tagged" [HCO·CO] cation complexes in the 1600-3500 cm region. The geometries and electronic ground states of these cation complexes are determined by their infrared spectra compared to the predications of theoretical calculations.

Dicarbonyls of Carbon and Methylidyne Cations.

The carbon suboxide cation CO and the protonated carbon suboxide HCO/DCO were produced in the gas phase. The vibrational spectra were measured via infrared photodissociation spectroscopy of their argon- or CO-tagged complexes. Spectroscopic evidence combined with state-of-the-art quantum chemical calculations indicate that both cations have a bent C symmetry and can be designated as dicarbonyls of a carbon cation and methylidyne cation, respectively.