Derivatization of Undecahalogenated -Dodecaborates [BXNH] (X = F-I): Attaching Isocyanate, Amidinium, and Formamide Functionalities.

Halogenated -dodecaborates are very robust and versatile weakly coordinating anions for numerous applications. The introduction of additional substituents, e.g.

Probing fragment ion reactivity towards functional groups on coordination polymer surfaces.

Functionalization of surface-grown coordination polymer layers by ion soft-landing of highly reactive molecular fragment ions is demonstrated. The ions form covalent bonds to terminal functional groups of the polymer at the vacuum interface, opening new perspectives for controlled bond formation using reactive ions.

Spontaneous ligand loss by soft landed [Ni(bpy)] ions on perfluorinated self-assembled monolayer surfaces.

Transition metal (TM) complexes are widely used in catalysis, photochemical energy conversion, and sensing. Understanding factors that affect ligand loss from TM complexes at interfaces is important both for generating catalytically-active undercoordinated TM complexes and for controlling the degradation pathways of photosensitizers and photoredox catalysts. Herein, we demonstrate that well-defined TM complexes prepared on surfaces using ion soft landing undergo substantial structural rearrangements resulting in ligand loss and formation of both stable and reactive undercoordinated species.

Probing the Electronic Structure of [BH] Dianion Encapsulated by an Octamethylcalix[4]pyrrole Molecule.

Despite being an important -borate in condensed phase boron chemistry, isolated [BH] is electronically unstable and has never been detected in the gas phase. Herein, we report a successful capture of this fleeting species through binding with an octamethylcalix[4]pyrrole (omC4P) molecule to form a stable gaseous omC4P·[BH] complex and its characterizations utilizing negative ion photoelectron spectroscopy (NIPES). The recorded NIPE spectrum, contributed by both omC4P and [BH], is deconvoluted by subtracting the omC4P contribution to yield a [BH] spectrum.

Generation and reactivity of the fragment ion [BIS(CN)] in the gas phase and on surfaces.

Gaseous fragment ions generated in mass spectrometers may be employed as "building blocks" for the synthesis of novel molecules on surfaces using ion soft-landing. A fundamental understanding of the reactivity of the fragment ions is required to control bond formation of deposited fragments in surface layers. The fragment ion [BX] (X = halogen) is formed by collision-induced dissociation (CID) from the precursor [BX] dianion.

Control of Intermediates and Products by Combining Droplet Reactions and Ion Soft-Landing.

Despite being recognized primarily as an analytical technique, mass spectrometry also has a large potential as a synthetic tool, enabling access to advanced synthetic routes by reactions in charged microdroplets or ionic thin layers. Such reactions are special and proceed primarily at surfaces of droplets and thin layers. Partial solvation of the reactants is usually considered to play an important role for reducing the activation barrier, but many mechanistic details still need to be clarified.

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).

Chemical Synthesis with Gaseous Molecular Ions: Harvesting [B Br N ] from a Mass Spectrometer.

Mass spectrometry frequently reveals the existence of transient gas phase ions that have not been synthesized in solution or in bulk. These elusive ions are, therefore, often considered to be primarily of analytical value in fundamental gas phase studies. Here, we provide proof-of-concept that the products of ion-molecule reactions in mass spectrometers may be collected on surfaces to generate condensed matter and thus serve as building blocks to synthesize new compounds.

Gas Phase Reactivity of [MoX] Dianions (X = Cl - I).

We investigate collision-induced dissociation (CID) of [MoX] (X = Cl, Br, I) and the reactivity of fragment ions of these precursors with background gases. Ion mobility measurements and theoretical calculations provide structural information for some of the observed ions. Sequential losses of MoX units dominate the dissociation pathways of [MoCl].

Hybrid Molecular Magnets with Lanthanide- and Countercation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate.

A series of {V}-nuclearity polyoxovanadate cages covalently functionalized with one or sandwiched by two phthalocyaninato (Pc) lanthanide (Ln) moieties V-O-Ln bonds were prepared and fully characterized for paramagnetic Ln = Sm-Er and diamagnetic Ln = Lu, including Y. The LnPc-functionalized {VO} cages with fully oxidized vanadium centers in the ground state were isolated as (BuN)[HVOCl(LnPc)] and (BuN)[HVOCl(LnPc)] compounds. As corroborated by a combined experimental (EPR, DC and AC SQUID, laser photolysis transient absorption spectroscopy, and electrochemistry) and computational (DFT, MD, and model Hamiltonian approach) methods, the compounds feature intra- and intermolecular electron transfer that is responsible for a partial reduction at V(3d) centers from V to V in the solid state and at high sample concentrations.

Binding of saturated and unsaturated C-hydrocarbons to the electrophilic anion [BBr]: a systematic mechanistic study.

The highly reactive gaseous ion [BBr] is a metal-free closed-shell anion which spontaneously forms covalent bonds with hydrocarbon molecules, including alkanes. Herein, we systematically investigate the reaction mechanism for binding of [BBr] to the five hexane isomers yielding [BBr(CH)], as well as to cyclohexane and several hexene isomers (yielding [BBr(CH)]) using collision-induced dissociation (CID), infrared photodissociation spectroscopy (IRPD) and computational methods. CID of the different [BBr(CH)] ions results in distinct fragmentation patterns dependent on the structure of the hexane isomer.

BX(H): exploring the limits of isotopologue selectivity of hydrogen adsorption.

We study the isotopologue-selective binding of dihydrogen at the undercoordinated boron site of BX (X = H, F, Cl, Br, I, CN) using quantum chemistry. With a Gibbs free energy of H attachment reaching up to 80 kJ mol (Δ at 300 K for X = CN), these sites are even more attractive than most undercoordinated metal centers studied so far. We thus believe that they can serve as an edge case close to the upper limit of isotopologue-selective H adsorption sites.

Isolated [B(CN)]: Small Yet Exceptionally Stable Nonmetal Dianion.

We report the observation of a small, yet remarkably stable, metal-free hexacyanodiborate dianion [B(CN)] in the gas phase. Negative ion photoelectron spectroscopy (NIPES) was employed to measure its spectra at multiple laser wavelengths, yielding a 1.9 eV electron binding energy (EBE) ─a remarkably high value of electronic stability and a ∼2.

Design and Performance of a Soft-Landing Instrument for Fragment Ion Deposition.

We report the development of a new high-flux electrospray ionization-based instrument for soft landing of mass-selected fragment ions onto surfaces. Collision-induced dissociation is performed in a collision cell positioned after the dual electrodynamic ion funnel assembly. The high duty cycle of the instrument enables high-coverage deposition of mass-selected fragment ions onto surfaces at a defined kinetic energy.

Anion-Anion Chemistry with Mass-Selected Molecular Fragments on Surfaces.

While reactions between ions and neutral molecules in the gas phase have been studied extensively, reactions between molecular ions of same polarity remain relatively unexplored. Herein we show that reactions between fragment ions generated in the gas phase and molecular ions of the same polarity are possible by soft-landing of both reagents on surfaces. The reactive [B I ] anion was deposited on a surface layer built up by landing the generally unreactive [B I ] .

Insights from Adsorption and Electron Modification Studies of Polyoxometalates on Surfaces for Molecular Memory Applications.

This Account highlights recent experimental and theoretical work focusing on the development of polyoxometalates (POMs) as possible active switching units in what may be called "molecule-based memory cells". Herein, we critically discuss how multiply charged vanadium-containing POMs, which exhibit stable metal-oxo bonds and are characterized by the excellent ability to change their redox states without significant structural distortions of the central polyoxoanion core, can be immobilized best and how they may work optimally at appropriate surfaces. Furthermore, we critically discuss important issues and challenges on the long way toward POM-based nanoelectronics.

Measuring Electronic Structure of Multiply Charged Anions to Understand Their Chemistry: A Case Study on Gaseous Polyhedral -Borate Dianions.

Research on multiply charged anions (MCAs) in the gas phase has been intensively performed during the past decades, mainly to understand fundamental molecular physics phenomena, for example, intramolecular Coulomb repulsion and existence of the repulsive Coulomb barrier. However, the relevance of these investigations with respect to understanding MCAs' chemistry appears often vague. Here, we discuss how insights into the electronic structure obtained from negative ion photoelectron spectroscopy (NIPES) combined with theoretical calculations and collision-induced dissociation can provide a fundamental understanding of the intrinsic chemical reactivity of MCAs and their fragments.

Synthesis, Structure, and Surface Adsorption Characteristics of a Polynuclear Mn-Yb Complex.

The controlled adsorption of polynuclear coordination compounds with specific structural and electronic characteristics on surfaces is crucial for the prospective implementation of molecule-surface interfaces into practical electronic devices. From this perspective, a neutral 3d,4f-coordination cluster [MnMnYbO(OH)(L·SMe)(OOCMe)]·2MeCN·3EtOH (·2MeCN·3EtOH), where L·SMe is a Schiff base, has been synthesized and fully characterized and its adsorption on two different solid substrates, gold and graphite, has been studied. The mixed-valence compound with a bilayered metal core structure and the structurally exposed thioether groups exhibits a substantially different surface bonding to metallic gold and semimetallic graphite substrates.

Relevance of π-Backbonding for the Reactivity of Electrophilic Anions [B X ] (X=F, Cl, Br, I, CN).

Electrophilic anions of type [B X ] posses a vacant positive boron binding site within the anion. In a comparatitve experimental and theoretical study, the reactivity of [B X ] with X=F, Cl, Br, I, CN is characterized towards different nucleophiles: (i) noble gases (NGs) as σ-donors and (ii) CO/N as σ-donor-π-acceptors. Temperature-dependent formation of [B X NG] indicates the enthalpy order (X=CN)>(X=Cl)≈(X=Br)>(X=I)≈(X=F) almost independent of the NG in good agreement with calculated trends.

Gaseous cyclodextrin--dodecaborate complexes χCD·BX (χ = α, β, and γ; X = F, Cl, Br, and I): electronic structures and intramolecular interactions.

A fundamental understanding of cyclodextrin-closo-dodecaborate inclusion complexes is of great interest in supramolecular chemistry. Herein, we report a systematic investigation on the electronic structures and intramolecular interactions of perhalogenated closo-dodecaborate dianions B12X122- (X = F, Cl, Br and I) binding to α-, β-, and γ-cyclodextrins (CDs) in the gas phase using combined negative ion photoelectron spectroscopy (NIPES) and density functional theory (DFT) calculations. The vertical detachment energy (VDE) of each complex and electronic stabilization of each dianion due to the CD binding (ΔVDE, relative to the corresponding isolated B12X122-) are determined from the experiments along α-, β- and γ-CD in the form of VDE (ΔVDE): 4.

New Perspectives in the Noble Gas Chemistry Opened by Electrophilic Anions.

Binding of noble gases (NGs) is commonly considered to be the realm of highly reactive electophiles with cationic or at least non-charged character. Herein, we summarize our latest results evidencing that the incorporation of a strongly electrophilic site within a rigid cage-like anionic structure offers several advantages that facilitate the binding of noble gases and stabilize the formed NG adducts. The anionic superelectrophiles investigated by us are based on the -dodecaborate dianion scaffold.

Cryogenic ion trap vibrational spectroscopy of the microhydrated sulfate dianions SO(HO).

Infrared photodissociation spectra of the D2-tagged microhydrated sulfate dianions with three to eight water molecules are presented over a broad spectral range that covers the OH stretching and H2O bending modes of the solvent molecules at higher energies, the sulfate stretching modes of the solute at intermediate energies and the intermolecular solute librational modes at the lowest energies. A low ion temperature combined with messenger-tagging ensures well-resolved vibrational spectra that allow for structure assignments based on a comparison to harmonic and anharmonic IR spectra from density functional theory (DFT) calculations. DFT ab initio molecular dynamics simulations are required to disentangle the broad and complex spectral signatures of microhydrated sulfate dianions in the OH stretching region and to identify systematic trends in the correlation of the strength and evolution of the solute-solvent and solvent-solvent interactions with cluster size.

{PVW}-Polyoxometalates Functionalized with Phthalocyaninato Y and Yb Moieties.

A tris(alkoxo)pyridine-augmented Wells-Dawson polyoxometalate (BuN)[] (WD = PVWO(OCH)C, Py = CHN) was functionalized with phthalocyaninato metal moieties ( where M = Y or Yb and Pc = CHN) to afford (BuN)[H()] compounds. High-resolution mass spectrometry was used to detect and identify the hybrid assembly. The magnetism studies reveal substantial differences between M = Yb (monomeric, single-ion paramagnetism) and M = Y (containing dimers, radical character).

Synthesis, Electronic Properties and Reactivity of [B X (NO )] (X=F-I) Dianions.

Nitro-functionalized undecahalogenated closo-dodecaborates [B X (NO )] were synthesized in high purities and characterized by NMR, IR, and Raman spectroscopy, single crystal X-diffraction, mass spectrometry, and gas-phase ion vibrational spectroscopy. The NO substituent leads to an enhanced electronic and electrochemical stability compared to the parent perhalogenated [B X ] (X=F-I) dianions evidenced by photoelectron spectroscopy, cyclic voltammetry, and quantum-chemical calculations. The stabilizing effect decreases from X=F to X=I.

Direct functionalization of C-H bonds by electrophilic anions.

Alkanes and [BX] (X = Cl, Br) are both stable compounds which are difficult to functionalize. Here we demonstrate the formation of a boron-carbon bond between these substances in a two-step process. Fragmentation of [BX] in the gas phase generates highly reactive [BX] ions which spontaneously react with alkanes.