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Fluorine is a common substituent in medicinal chemistry and is found in up to 50% of the most profitable drugs. In this study, a statistical analysis of the nature, geometry, and frequency of hydrogen bonds (HBs) formed between the aromatic and aliphatic C-F groups of small molecules and biological targets found in the Protein Data Bank (PDB) repository was presented. Interaction energies were calculated for those complexes using three different approaches. The obtained results indicated that the interaction energy of F-containing HBs is determined by the donor-acceptor distance and not by the angles. Moreover, no significant relationship between the energies of HBs with fluorine and the donor type was found, implying that fluorine is a weak HB acceptor for all types of HB donors. However, the statistical analysis of the PDB repository revealed that the most populated geometric parameters of HBs did not match the calculated energetic optima. In a nutshell, HBs containing fluorine are forced to form due to the stronger ligand-receptor neighboring interactions, which make fluorine the "donor's last resort".

Fluoroalkyl groups profoundly affect the physical properties of pharmaceuticals and influence almost all metrics associated with their pharmacokinetic and pharmacodynamic profile 1-4 . Drug candidates increasingly contain trifluoromethyl (CF 3 ) and difluoromethyl (CF 2 H) groups, and the same trend in agrochemical development shows that the effect of fluoroalkylation translates across human, insect and plant life 5,6 . New fluoroalkylation reactions have undoubtedly stimulated this shift; however, methods that directly convert C-H bonds into C-CF 2 X groups (where X is F or H) in complex drug-like molecules are rare 7-13 . Pyridines are the most common aromatic heterocycles in pharmaceuticals 14 , but only one approach-via fluoroalkyl radicals-is viable for achieving pyridyl C-H fluoroalkylation in the elaborate structures encountered during drug development 15-17 . Here we develop a set of bench-stable fluoroalkylphosphines that directly convert the C-H bonds in pyridine building blocks, drug-like fragments and pharmaceuticals into fluoroalkyl derivatives. No preinstalled functional groups or directing groups are required. The reaction tolerates a variety of sterically and electronically distinct pyridines, and is exclusively selective for the 4-position in most cases. The reaction proceeds through initial formation of phosphonium salts followed by sp 2 -sp 3 coupling of phosphorus ligands-an underdeveloped manifold for forming C-C bonds.

Frequently referred to as the 'magic methyl effect', the installation of methyl groups-especially adjacent (α) to heteroatoms-has been shown to dramatically increase the potency of biologically active molecules 1-3 . However, existing methylation methods show limited scope and have not been demonstrated in complex settings 1 . Here we report a regioselective and chemoselective oxidative C(sp 3 )-H methylation method that is compatible with late-stage functionalization of drug scaffolds and natural products. This combines a highly site-selective and chemoselective C-H hydroxylation with a mild, functional-group-tolerant methylation. Using a small-molecule manganese catalyst, Mn(CF 3 PDP), at low loading (at a substrate/catalyst ratio of 200) affords targeted C-H hydroxylation on heterocyclic cores, while preserving electron-neutral and electron-rich aryls. Fluorine- or Lewis-acid-assisted formation of reactive iminium or oxonium intermediates enables the use of a mildly nucleophilic organoaluminium methylating reagent that preserves other electrophilic functionalities on the substrate. We show this late-stage C(sp 3 )-H methylation on 41 substrates housing 16 different medicinally important cores that include electron-rich aryls, heterocycles, carbonyls and amines. Eighteen pharmacologically relevant molecules with competing sites-including drugs (for example, tedizolid) and natural products-are methylated site-selectively at the most electron rich, least sterically hindered position. We demonstrate the syntheses of two magic methyl substrates-an inverse agonist for the nuclear receptor RORc and an antagonist of the sphingosine-1-phosphate receptor-1-via late-stage methylation from the drug or its advanced precursor. We also show a remote methylation of the B-ring carbocycle of an abiraterone analogue. The ability to methylate such complex molecules at late stages will reduce synthetic effort and thereby expedite broader exploration of the magic methyl effect in pursuit of new small-molecule therapeutics and chemical probes.

Purpose: To reveal the underlying mechanism inducing the opposite trends of surface composition enrichment of spray dried amorphous solid dispersions (ASD) of sorafenib and regorafenib, two compounds only differ in hydrogen to fluorine substitution., Methods: Sorafenib/PVP and regorafenib/PVP ASDs were prepared by spray drying. Morphology of ASDs was visually inspected and examined by SEM. The surface compositions of ASDs were analyzed by XPS. Glass transition temperature (T g ) of ASDs was determined by DSC. Water vapor sorption isotherms of ASDs were studied by moisture sorption analyzer. Molecular interaction between the drug and the polymer was analyzed by solution NMR., Results: In 10% and 20% drug loading sorafenib/PVP ASDs, short time moisture exposure induced PVP enrichment on the surface, and the appearance of initial ASDs powder became gel-like after water uptake. While in 30% sorafenib/PVP and any regorafenib/PVP ASDs regardless of drug loading, moisture exposure induced surface drug enrichment, while their powder-like appearance and average particle size remained unchanged. Meanwhile, sorafenib/PVP had similar water vapor sorption isotherms as regorafenib/PVP, before and after moisture induced phase separation. NMR study demonstrated a hex atomic ring H-bonding interaction between the drug and PVP, with a 1:1 drug: monomer stoichiometry molar ratio, which persisted in sorafenib/PVP but not regorafenib/PVP system under 95%RH moisture., Conclusions: Moisture exposure could lead to drug or polymer enrichment on the surface of ASDs, while the viability of drug-polymer interaction persisting in water environment contributed to such surface composition enrichment.

Gold nanoparticles (AuNPs) covered with mixtures of immiscible ligands present potentially anisotropic surfaces that can modulate their interactions at complex nano-bio interfaces. Mixed, self-assembled, monolayer (SAM)-protected AuNPs, prepared with incompatible hydrocarbon and fluorocarbon amphiphilic ligands, are used here to probe the molecular basis of surface phase separation and disclose the role of fluorinated ligands on the interaction with lipid model membranes and cells, by integrating in silico and experimental approaches. These results indicate that the presence of fluorinated amphiphilic ligands enhances the membrane binding ability and cellular uptake of gold nanoparticles with respect to those coated only with hydrogenated amphiphilic ligands. For mixed monolayers, computational results suggest that ligand phase separation occurs on the gold surface, and the resulting anisotropy affects the number of contacts and adhesion energies with a membrane bilayer. This reflects in a diverse membrane interaction for NPs with different surface morphologies, as determined by surface plasmon resonance, as well as differential effects on cells, as observed by flow cytometry and confocal microscopy. Overall, limited changes in monolayer features can significantly affect NP surface interfacial properties, which, in turn, affect the interaction of SAM-AuNPs with cellular membranes and subsequent effects on cells., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objective: Given the growing interest in fluorine, it is necessary to develop new multi-tuned RF coils. Therefore, our objective is to design a simple and versatile double-tuned RF coil that can be used as a transmitter and receiver double-tuned coil ( 1 H and 19 F) or as transmitter-only double-tuned coil., Materials and Methods: A high-pass eight-element birdcage coil was built for 1 H and 19 F for a 7 T scanner. PIN diodes and cable traps to block unwanted common mode currents in cables were introduced to confer more flexibility to the coil. S-parameters and quality factor were measured in workbench and signal to noise ratio as well as signal intensity profiles in imaging experiments., Results: Bench measurements show S11 values less than - 33 dB, S21 lower than - 13 dB and quality factors ratio of the order of 1.8 that are in agreement with good performances of a RF coil, as well as values of - 39 dB for 19 F and - 30 dB for 1 H as good detuning values. Signal intensity profiles prove excellent homogeneity at 1 H and 19 F., Discussion: We present a simple structure of a double-tuned high-pass birdcage coil tuned to 1 H and 19 F that shows a great uniformity and sensitivity for 19 F.

Aryl fluorides are widely used in the pharmaceutical and agrochemical industries, and recent advances have enabled their synthesis through the conversion of various functional groups. However, there is a lack of general methods for direct aromatic carbon-hydrogen (C-H) fluorination. Conventional methods require the use of either strong fluorinating reagents, which are often unselective and difficult to handle, such as elemental fluorine, or less reactive reagents that attack only the most activated arenes, which reduces the substrate scope. A method for the direct fluorination of aromatic C-H bonds could facilitate access to fluorinated derivatives of functional molecules that would otherwise be difficult to produce. For example, drug candidates with improved properties, such as increased metabolic stability or better blood-brain-barrier penetration, may become available. Here we describe an approach to catalysis and the resulting development of an undirected, palladium-catalysed method for aromatic C-H fluorination using mild electrophilic fluorinating reagents. The reaction involves a mode of catalysis that is unusual in aromatic C-H functionalization because no organometallic intermediate is formed; instead, a reactive transition-metal-fluoride electrophile is generated catalytically for the fluorination of arenes that do not otherwise react with mild fluorinating reagents. The scope and functional-group tolerance of this reaction could provide access to functional fluorinated molecules in pharmaceutical and agrochemical development that would otherwise not be readily accessible.

Fluorine-19 has high NMR detection sensitivity-similar to that of protons-owing to its large gyromagnetic ratio and high natural abundance (100 %). Unlike protons, however, fluorine-19 ( 19 F) has a negligible occurrence in biological objects, as well as a more sensitive chemical shift. As a result, in vivo 19 F NMR spectroscopy and MR imaging offer advantages of negligible background signal and sensitive reporting of the local molecular environment. Here we report on NMR hyperpolarization of 19 F nuclei using reversible exchange reactions with parahydrogen gas as the source of nuclear spin order. NMR signals of 3-fluoropyridine were enhanced by ≈100 fold, corresponding to 0.3 % 19 F nuclear spin polarization (at 9.4 T), using about 50 % parahydrogen. While future optimization efforts will likely significantly increase the hyperpolarization levels, we already demonstrate the utility of 19 F hyperpolarization for high-resolution hyperpolarized 19 F imaging and hyperpolarized 19 F pH sensing., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The copper-catalyzed H-F insertion into α-diazocarbonyl compounds is described using potassium fluoride (KF) and hexafluoroisopropanol. Access to complex α-fluorocarbonyl derivatives is achieved under mild conditions, and the method is readily adapted to radiofluorination with [(18)F]KF. This late-stage strategy provides an attractive route to (18)F-labeled biomolecules.

With the aid of breakthroughs in nanoscience and nanotechnology, it is imperative to develop metal oxide semiconductors through visible light-driven hydrogen generation. In this study, TiOF2 was incorporated as an n-type F-dopant source to TiO2 mesocrystals (TMCs) with visible-light absorption during the topotactic transformation. The crystal growth, structural change, and dynamic morphological evolution, from the initial intermediate NH4 TiOF3 to HTiOF3, TiOF2, and F-doped TMCs, were verified through in situ temperature-dependent techniques to elucidate the doping mechanism from intermediate TiOF2. The visible-light efficiencies of photocatalytic hydrogen were dependent on the contents of the dopant as compared with the pure TMC and a controled reference. Using femtosecond time-resolved diffuse reflectance spectroscopy, the charge-transfer dynamics were monitored to confirm the improvement of charge separation after doping., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Herein we report the intramolecular arene C-H and C-F bond oxygenation by tetranuclear iron complexes. Treatment of [LFe3(PhPz)3OFe][OTf]2 (1) or its fluorinated analog [LFe3(F2ArPz)3OFe][OTf]2 (5) with iodosobenzene results in the regioselective hydroxylation of a bridging pyrazolate ligand, converting a C-H or C-F bond into a C-O bond. The observed reactivity suggests the formation of terminal and reactive Fe-oxo intermediates. With the possibility of intramolecular electron transfer within clusters in 1 and 5, different reaction pathways (Fe(IV)-oxo vs Fe(III)-oxo) might be responsible for the observed arene hydroxylation.

The excess electron attachment to the HAlF4 superacid molecule was studied by employing ab initio CCSD(T) and MP2 methods and a purposely suited aug-cc-pVTZ+4s4p3d basis set. The results indicate that the HAlF4 molecule, due to its polarity, may attract a distant excess electron and form a dipole-bound anionic state whose vertical electron binding energy is 1106 cm(-1). The initially formed (HAlF4)(-) anion of a dipole-bound nature undergoes an immediate structural reorganization driven by the (AlF4)(-) strongly-bound superhalogen anion formation. The potential energy surface analysis leads to the conclusion that the (HAlF4)(-) → (AlF4)(-) + H transformation should proceed spontaneously and involve the simultaneous structure relaxation of the AlF4 moiety (in the direction approaching a tetrahedral geometry) and the excess electron density migration from the area outside the molecular framework to the valence AlF4 region. The fragmentation of the HAlF4 superacid molecule is predicted to be the final effect of the excess electron attachment process. In addition, the important antenna role of the initially formed (HAlF4)(-) dipole-bound anionic state is discussed.

The nuclear electronic orbital (NEO) reduced explicitly correlated Hartree-Fock (RXCHF) approach couples select electronic orbitals to the nuclear orbital via Gaussian-type geminal functions. This approach is extended to enable the use of a restricted basis set for the explicitly correlated electronic orbitals and an open-shell treatment for the other electronic orbitals. The working equations are derived and the implementation is discussed for both extensions. The RXCHF method with a restricted basis set is applied to HCN and FHF(-) and is shown to agree quantitatively with results from RXCHF calculations with a full basis set. The number of many-particle integrals that must be calculated for these two molecules is reduced by over an order of magnitude with essentially no loss in accuracy, and the reduction factor will increase substantially for larger systems. Typically, the computational cost of RXCHF calculations with restricted basis sets will scale in terms of the number of basis functions centered on the quantum nucleus and the covalently bonded neighbor(s). In addition, the RXCHF method with an odd number of electrons that are not explicitly correlated to the nuclear orbital is implemented using a restricted open-shell formalism for these electrons. This method is applied to HCN(+), and the nuclear densities are in qualitative agreement with grid-based calculations. Future work will focus on the significance of nonadiabatic effects in molecular systems and the further enhancement of the NEO-RXCHF approach to accurately describe such effects.

Ab initio MP2/aug'-cc-pVTZ calculations were performed to investigate the pnicogen-bonded complexes F(4-n)H(n)P(+):N-base, for n = 0-3, each with a linear or nearly linear F-P···N alignment. The nitrogen bases include the sp(3) bases NH3, NClH2, NFH2, NCl2H, NCl3, NFCl2, NF2H, NF2Cl, and NF3 and the sp bases NCNH2, NCCH3, NP, NCOH, NCCl, NCH, NCF, NCCN, and N2. The binding energies vary between -20 and -180 kJ·mol(-1), while the P-N distances vary from 1.89 to 3.01 Å. In each series of complexes, binding energies decrease exponentially as the P-N distance increases, provided that complexes with sp(3) and sp hybridized bases are treated separately. Different patterns are observed for the change in the binding energies of complexes with a particular base as the number of F atoms in the acid changes. Thus, the particular acid-base pair is a factor in determining the binding energies of these complexes. Three different charge-transfer interactions stabilize these complexes. These arise from the nitrogen lone pair to the σ*P-F(ax), σ*P-F(eq), and σ*P-H(eq) orbitals. The dominant single charge-transfer energy in all complexes is N(lp) → σ*P-F(ax). However, since there are three N(lp) → σ*P-F(eq) charge-transfer interactions in complexes with F4P(+) and two in complexes with F3HP(+), the sum of the N(lp) → σ*P-F(eq) charge-transfer energies is greater than the N(lp) → σ*P-F(ax) charge-transfer energies in the former complexes, and similar to the N(lp) → σ*P-F(ax) energies in the latter. The total charge-transfer energies of all complexes decrease exponentially as the P-N distance increases. Coupling constants (1p)J(P-N) across the pnicogen bond vary with the P-N distance, but different patterns are observed for complexes with F4P(+) and complexes of the sp(3) bases with F3HP(+). These initially increase as the P-N distance decreases, reach a maximum, and then decrease with decreasing P-N distance as the P···N bond acquires increased covalent character. For the remaining complexes, (1p)J(P-N) increases with decreasing P-N distance. Complexation increases the P-F(ax) distance and (1)J(P-F(ax)) relative to the corresponding isolated ion. (1)J(P-F(ax)) correlates quadratically with the P-N distance.

An operationally simple and selective method for the direct conversion of benzylic C-H to C-F to obtain mono- and difluoromethylated arenes using Selectfluor™ as a fluorine source is developed. Persulfate can be used to selectively activate benzylic hydrogen atoms toward C-F bond formation without the aid of transition metal catalysts.

Ab initio MP2/aug'-cc-pVTZ calculations have been carried out on the pnicogen-bonded complexes H(n)F(5-n)P:N-base, for n = 0-5 and nitrogen bases NC(-), NCLi, NP, NCH, and NCF. The structures of these complexes have either C(4v) or C(2v) symmetry with one exception. P-N distances and interaction energies vary dramatically in these complexes, while F(ax)-P-F(eq) angles in complexes with PF5 vary from 91° at short P-N distances to 100° at long distances. The value of this angle approaches the F(ax)-P-F(eq) angle of 102° computed for the Berry pseudorotation transition structure which interconverts axial and equatorial F atoms of PF5. The computed distances and F(ax)-P-F(eq) angles in complexes F5P:N-base are consistent with experimental CSD data. For a fixed acid, interaction energies decrease in the order NC(-) > NCLi > NP > NCH > NCF. In contrast, for a fixed base, there is no single pattern for the variations in distances and interaction energies as a function of the acid. This suggests that there are multiple factors that influence these properties. The dominant factor appears to be the number of F atoms in equatorial positions, and then a linear F(ax)-P···N rather than H(ax)-P···N alignment. The acids may be grouped into pairs (PF5, PHF4) with four equatorial F atoms, then (PH4F, PH2F3) with F(ax)-P···N linear, and then (PH3F2 and PH5) with H(ax)-P···N linear. The electron-donating ability of the base is also a factor in determining the structures and interaction energies of these complexes. Charge transfer from the N lone pair to the σ* P-A(ax) orbital stabilizes H(n)F(5-n)P:N-base complexes, with A(ax) either F(ax) or H(ax). The total charge-transfer energies correlate with the interaction energies of these complexes. Spin-spin coupling constants (1p)J(P-N) for (PF5, PHF4) complexes with nitrogen bases are negative with the strongest bases NC(-) and NCLi but positive for the remaining bases. Complexes of (PH4F, PH2F3) with these same two strong bases and H4FP:NP have positive (1p)J(P-N) values but negative values for the remaining bases. (PH5, PH3F2) have negative values of (1p)J(P-N) only for complexes with NC(-). Values of (1)J(P-F(ax)) and (1)J(P-H(ax)) correlate with the P-F(ax) and P-H(ax) distances, respectively.

Fluorination reactions are essential to modern medicinal chemistry, thus providing a means to block site-selective metabolic degradation of drugs and access radiotracers for positron emission tomography imaging. Despite current sophistication in fluorination reagents and processes, the fluorination of unactivated CH bonds remains a significant challenge. Reported herein is a convenient and economic process for direct fluorination of unactivated CH bonds that exploits the hydrogen abstracting ability of a decatungstate photocatalyst in combination with the mild fluorine atom transfer reagent N-fluorobenzenesulfonimide. This operationally straightforward reaction provides direct access to a wide range of fluorinated organic molecules, including structurally complex natural products, acyl fluorides, and fluorinated amino acid derivatives., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The prototypical F + H2 → HF + H reaction possesses a substantial energetic barrier (~800 K) and might therefore be expected to slow to a negligible rate at low temperatures. It is, however, the only source of interstellar HF, which has been detected in a wide range of cold (10-100 K) environments. In fact, the reaction does take place efficiently at low temperatures due to quantum-mechanical tunnelling. Rate constant measurements at such temperatures have essentially been limited to fast barrierless reactions, such as those between two radicals. Using uniform supersonic hydrogen flows we can now report direct experimental measurements of the rate of this reaction down to a temperature of 11 K, in remarkable agreement with state-of-the-art quantum reactive scattering calculations. The results will allow a stronger link to be made between observations of interstellar HF and the abundance of the most common interstellar molecule, H2, and hence a more accurate estimation of the total mass of astronomical objects.

The hydrogen abstraction reaction of fluorine with ammonia represents a true chemical challenge because it is very fast, is followed by secondary abstraction reactions, which are also extremely fast, and presents an experimental/theoretical controversy about rate coefficients. Using a previously developed full-dimensional analytical potential energy surface, we found that the F + NH3 → HF + NH2 system is a barrierless reaction with intermediate complexes in the entry and exit channels. In order to understand the reactivity of the title reaction, thermal rate coefficidents were calculated using two approaches: ring polymer molecular dynamics and quasi-classical trajectory calculations, and these were compared with available experimental data for the common temperature range 276-327 K. The theoretical results obtained show behavior practically independent of temperature, reproducing Walther-Wagner's experiment, but in contrast with Persky's more recent experiment. However, quantitatively, our results are 1 order of magnitude larger than those of Walther-Wagner and reasonably agree with the Persky at the lowest temperature, questioning so Walther-Wagner's older data. At present, the reason for this discrepancy is not clear, although we point out some possible reasons in the light of current theoretical calculations.

Fluorination is a reaction that is useful in improving the chemical stability and changing the binding affinity of biologically active compounds. The protocol described here can be used to replace aliphatic, C(sp(3))-H hydrogen in small molecules with fluorine. Notably, isolated methylene groups and unactivated benzylic sites are accessible. The method uses readily available manganese porphyrin and manganese salen catalysts and various fluoride ion reagents, including silver fluoride (AgF), tetrabutylammonium fluoride and triethylamine trihydrofluoride (TREAT·HF), as the source of fluorine. Typically, the reactions afford 50-70% yield of mono-fluorinated products in one step. Two representative examples, the fragrance component celestolide and the nonsteroidal anti-inflammatory drug ibuprofen, are described; they produced useful isolated quantities (250-300 mg, ~50% yield) of fluorinated material over periods of 1-8 h. The procedures are performed in a typical fume hood using ordinary laboratory glassware. No special precautions to rigorously exclude water are required.

The existence of the rare six-membered and intramolecular C-H···F-C hydrogen-bond has been experimentally proven in the gas phase and in the solid state recently. However, the effect of the substituents on this C-H···F-C hydrogen-bond system has never been reported. In view of the importance of this type of C-H···F-C H-bonding whose weak interaction has been found critical in nanotechnology and biological systems, the nine functional groups composed of electron donating and electron withdrawing groups are inserted into this C-H···F-C interaction to study the group effect on the hydrogen bonding. Group effects on this C-H···F-C H-bonding system have been found, and their effects on the H-bonding system have been found to be tunable.

The chemical variety present in the organic electronics literature has motivated us to investigate potential nonbonding interactions often incorporated into conformational "locking" schemes. We examine a variety of potential interactions, including oxygen-sulfur, nitrogen-sulfur, and fluorine-sulfur, using accurate quantum-chemical wave function methods and noncovalent interaction (NCI) analysis on a selection of high-performing conjugated polymers and small molecules found in the literature. In addition, we evaluate a set of nonbonding interactions occurring between various heterocyclic and pendant atoms taken from a group of representative π-conjugated molecules. Together with our survey and set of interactions, it is determined that while many nonbonding interactions possess weak binding capabilities, nontraditional hydrogen-bonding interactions, oxygen-hydrogen (CH···O) and nitrogen-hydrogen (CH···N), are alone in inducing conformational control and enhanced planarity along a polymer or small molecule backbone at room temperature.

Supported fluorine-doped alpha-Fe2O3 nanomaterials were synthesized by Plasma Enhanced-Chemical Vapor Deposition (PE-CVD) at temperatures between 300 and 500 degrees C, using a fluorinated iron(II) diketonate-diamine compound as a single-source precursor for both Fe and F. The system structure, morphology and composition were thoroughly investigated by various characterization techniques, highlighting the possibility of controlling the fluorine doping level by varying the sole growth temperature. Photocatalytic H2 production from water/ethanol solutions under simulated solar irradiation evidenced promising gas evolution rates, candidating the present PE-CVD approach as a valuable strategy to fabricate highly active supported materials.

First-principles calculations have been used to investigate the structural and electronic properties of graphene supported on functionalized hexagonal boron nitride (h-BN) with hydrogen and fluorine atoms. Our results show that the hydrogenation and fluorination of the h-BN substrate modify the electronic properties of graphene. Interactions of graphene with fully hydrogenated or fully fluorinated h-BN and half-hydrogenated and half-fluorinated h-BN with H at N sites and F at the B sites can lead to n- or p-type doping of graphene. The different doping effect may be attributed to the significant charge transfer from graphene to the substrate. Interestingly, when graphene is supported on the functionalized h-BN with H at B sites and F at N sites (G/HBNF), a finite band gap of 79 meV in graphene is opened due to the equivalence breaking of two sublattices of graphene, and can be effectively modulated by changing the interlayer spacing, increasing the number of functionalized BN layers, and applying an external electric field. More importantly, the modification of the band gap in G/HBNF with a functionalized BN bilayer by the electric field is more pronounced than that of the single-layer h-BN, which is increased to 408 meV with 0.8 V Å(-1). Thus, graphene on chemically modified h-BN with a tunable and sizeable band gap may provide a novel way for fabricating high-performance graphene-based nanodevices.

The present case study aims at calculating the equilibrium conformer compositions for 2X-ethanol and 2X-phenol (X = F, Cl) in solution, and exploring the effect of the applied theoretical method and basis set on the obtained results, as well as considering the usefulness of the continuum solvent approach in comparison with the explicit solvent Monte Carlo model utilizing the free energy perturbation method. Gas-phase optimizations at the DFT/B97D/aug-cc-pvtz and ab initio MP2/aug-cc-pvtz levels predicted structures in good agreement with the available experimental data for three test molecules. Because in-solution geometries change only slightly according to the IEF-PCM continuum solvent calculations in carbon tetrachloride and water, the two theoretical levels were applied further on, and complete basis set (CBS) relative internal free energies were estimated for the conformers under study. The predicted OCCF gauche/trans ratio for 2F-ethanol was well reproduced in comparison with available experimental compositions. The predominant gauche structure maintains an intramolecular hydrogen bond in carbon tetrachloride (HB structure), whereas HB and NoHB gauche conformers appear in nearly the same fraction in aqueous solution. The internally hydrogen-bonded conformer is predominant also for 2X-phenol species, as calculated on the basis of relative CBS internal free energies and IEF-PCM and FEP/MC solvation free energies. Use of a trihydrate supermolecule model for 2F-ethanol conformers leads to the prediction of the aqueous-solution composition in contrast to the experiment. Solution structure modeling predicts weak hydrogen-bond formation capacity for both the covalently bound F and Cl atoms, even in conformations where they are fully exposed to hydration.

The effects of electron and hole doping on the magnetic properties of hydrogenated and fluorinated graphene structures are theoretically investigated by additional charge mimic. The studied hydrogenated and fluorinated graphene with different electronic structures display different relations between magnetism and charge, in which the spin moment of the former has the maximum value without charge, followed by linearly and symmetrically decreasing with increase of the positive and negative charge (hole and electron doping), while the latter continuously but not linearly increases its spin moment with the charge variation and finally achieves a maximum at certain positive charge doping. Moreover, the phase transition from ferromagnetism to nonmagnetism occurs. With the analysis of the spin-polarized band structures, the electron and hole doping effects on spin moment in the hydrogenated graphene mainly arise from the shifts of the Fermi level, while that in the fluorinated graphene not only results from the shifts of Fermi level, but also from the relative shifts between up- and down-spin band lines. The discovery of the effects of electron and hole doping on magnetism provides fundamental insight on functionalized graphene, rendering new promising potentials for unique spintronics applications.

A theoretical study of the complexes formed between HArF and XH2P (X=F, Cl, and Br) has been carried out using ab initio methods (MP2/aug-cc-pVDZ, MP2/aug-cc-pVTZ, and CCSD(T)/aug-cc-pVTZ). Three minima were found, which correspond to a hydrogen-bonded complex (I), a pnicogen-bonded complex (II), and a halogen-bonded complex (III). The pnicogen-bonded complex is the most stable, followed by the hydrogen-bonded complex, and the halogen-bonded complex is the least stable. The Ar-H bond is enhanced in FH2P-HArF-I complex and exhibits a blue shift, while it is weakened in ClH2P-HArF-I and BrH2P-HArF-I complexes and shows a red shift. A blue shift is also found for the distant Ar-H bond in the halogen-bonded and pnicogen-bonded complexes. These complexes have been understood with the electrostatic potentials and symmetry adapted perturbation theory (SAPT) method., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Although graphene's physical structure is a single atom thick, two-dimensional, hexagonal crystal of sp(2) bonded carbon, this simple description belies the myriad interesting and complex physical properties attributed to this fascinating material. Because of its unusual electronic structure and superlative properties, graphene serves as a leading candidate for many next generation technologies including high frequency electronics, broadband photodetectors, biological and gas sensors, and transparent conductive coatings. Despite this promise, researchers could apply graphene more routinely in real-world technologies if they could chemically adjust graphene's electronic properties. For example, the covalent modification of graphene to create a band gap comparable to silicon (∼1 eV) would enable its use in digital electronics, and larger band gaps would provide new opportunities for graphene-based photonics. Toward this end, researchers have focused considerable effort on the chemical functionalization of graphene. Due to its high thermodynamic stability and chemical inertness, new methods and techniques are required to create covalent bonds without promoting undesirable side reactions or irreversible damage to the underlying carbon lattice. In this Account, we review and discuss recent theoretical and experimental work studying covalent modifications to graphene using gas phase atomic radicals. Atomic radicals have sufficient energy to overcome the kinetic and thermodynamic barriers associated with covalent reactions on the basal plane of graphene but lack the energy required to break the C-C sigma bonds that would destroy the carbon lattice. Furthermore, because they are atomic species, radicals substantially reduce the likelihood of unwanted side reactions that confound other covalent chemistries. Overall, these methods based on atomic radicals show promise for the homogeneous functionalization of graphene and the production of new classes of two-dimensional materials with fundamentally different electronic and physical properties. Specifically, we focus on recent studies of the addition of atomic hydrogen, fluorine, and oxygen to the basal plane of graphene. In each of these reactions, a high energy, activating step initiates the process, breaking the local π structure and distorting the surrounding lattice. Scanning tunneling microscopy experiments reveal that substrate mediated interactions often dominate when the initial binding event occurs. We then compare these substrate effects with the results of theoretical studies that typically assume a vacuum environment. As the surface coverage increases, clusters often form around the initial distortion, and the stoichiometric composition of the saturated end product depends strongly on both the substrate and reactant species. In addition to these chemical and structural observations, we review how covalent modification can extend the range of physical properties that are achievable in two-dimensional materials.

An amine/amide mixed covalent organic tetrahedral cage 1 (H(12)) was synthesized and characterized. The H(12) cage contains 12 amide NH groups plus four tertiary amine N groups, the latter of which are positioned in a pseudo-tetrahedral array. Crystallographic findings indicate that the tetrahedral host can adopt either a pseudo-C(3) symmetric "compressed tetrahedron" structure, or one in which there are two sets of three stacked pyridine units related by a pseudo-S(4) axis. The latter conformation is ideal for encapsulating small pentameric clusters, either a water molecule or a fluoride ion surrounded by a tetrahedral array of water molecules, i.e., H(2)O·4H(2)O or F(-)·4H(2)O, as observed crystallographically. In solution, however, (19)F NMR spectroscopy indicates that H(12) encapsulates fluoride ion through direct amide hydrogen bonding. By collectively combining one-dimensional (1)H, (13)C, and (19)F with two-dimensional (1)H-(1)H COSY, (1)H-(13)C HSQC, and (1)H-(19)F HETCOR NMR techniques, the solution binding mode of fluoride can be ascertained as consisting of four sets of independent structural subunits with C(3) symmetry. A complex deuterium exchange process for the fluoride complex can also be unraveled by multiple NMR techniques.

The correlations between the structural and electronic properties of the monolayer clusters M₃ (where M = Ni, Pd, Pt) and the sandwich complexes M₃(C₆R₆)₂ (where M = Ni, Pd, Pt; R = H, F) were studied by performing quantum-chemical calculations. All of the sandwich complexes are strongly donating and backdonating metal-ligand bonding structures. The influence of the ligand as well as significant variations in the M-C, M-M, and C-C bond lengths and binding energies were examined to obtain a qualitative and quantitative picture of the intramolecular interactions in C₆R₆-M₃. Our theoretical investigations show that the binding energies of these sandwich complexes gradually decrease from Ni to Pt as well as from H to F, which can be explained via the frontier orbitals of the clusters M₃ and C₆R₆.

The mechanism of the gas-phase reactions of SiH(n)(+) (n = 1,2) with NF(3) were investigated by ab initio calculations at the MP2 and CAS-MCSCF level of theory. In the reaction of SiH(+), the kinetically relevant intermediates are the two isomeric forms of fluorine-coordinated intermediate HSi-F-NF(2)(+). These species arise from the exoergic attack of SiH(+) to one of the F atoms of NF(3) and undergo two competitive processes, namely an isomerization and subsequent dissociation into SiF(+) + HNF(2) , and a singlet-triplet crossing so to form the spin-forbidden products HSiF(+) + NF(2). The reaction of SiH(2)(+) with NF(3) involves instead the concomitant formation of the nitrogen-coordinated complex H(2)Si-NF(3)(+) and of the fluorine-coordinated complex H(2)Si-F-NF(2)(+). The latter isomer directly dissociates into NF(2)(+) + H(2)SiF, whereas the former species preferably undergoes the passage through a conical intersection point so to form a H(2) SiF-NF(2)(+) isomer, which eventually dissociates into H(2)SiF(+) and NF(2)., (Copyright © 2012 Wiley Periodicals, Inc.)

Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate the influence of F-H···F hydrogen bonds on the P···N pnicogen bond in complexes nFH:(H2FP:NFH2) for n = 1-2, and a selected complex with n = 3. The NBO analysis indicates that the N(lp) → P-Fσ* charge-transfer transition has a much greater stabilizing effect than the P(lp) → N-Fσ* transition. When hydrogen bonding occurs at P-F, charge transfer associated with the pnicogen bond and the hydrogen bond are in the same direction but are in opposite directions when hydrogen bonding occurs at N-F. As a result, the formation of F-H···F hydrogen bonds at P-F leads to shorter P···N distances, increased strength of P···N bonds, and synergistic energetic effects; hydrogen bonding at N-F has opposite effects. (31)P and (15)N chemical shieldings do not correlate with charges on P and N, respectively, but (31)P shieldings correlate quadratically with the P-N distance. (1p)J(P-N) coupling constants do not correlate with the intermolecular P-N distance. However, when hydrogen bonding occurs only at P-F, (1p)J(P-N) decreases in absolute value as the P-N distance decreases, thereby approaching (1)J(P-N) for H2P-NH2. However, the P···N bond in 3FH:(H2FP:NFH2) has little covalent character, unlike the P···P bond in the corresponding complex 3FH:(PH2F)2.

The F + H(D)O → HF(DF) + O reactions have been studied using quasi-classical trajectory (QCT) calculation method, based on the three different potential energy surfaces (PESs) of Gomez-Carrasco et al. (J Chem Phys 2004, 121:4605; J Chem Phys 2005, 123:114310; Chem Phys Lett 2007, 435:188). Facilitated with the analysis of the QCT results, the pictures for product scattering and product polarizations have been presented to investigate the vector correlations in the two reactions, with effects of isotope substitution and electronic state as well as collision energy being revealed at a chemical stereodynamical level.

A novel interaction mechanism between HArF and BeH(2) has been validated and characterized with quantum chemical calculations at the MP2/aug-cc-pVQZ level. They can interact through beryllium bonding formed between the positively charged Be atom in BeH(2) and the negatively charged F atom in HArF, besides through dihydrogen bonding. The former (61.3 kcal/mol) is much stronger than the latter (5.9 kcal/mol). The red shift is found for the associated H-Ar stretch in the dihydrogen bonding, whereas the big blue shift is observed for the distant H-Ar stretch in the beryllium bonding. The blue shift of the distant H-Ar stretch is affected greatly by computational methods. It is calculated to be 712 cm(-1) at the CCSD(T)/6-311++G(3df,2p) level, which appears to be the largest blue shift validated for any weakly bound complex yet. The substitution effect on the beryllium bond is similar to that on hydrogen bonds. The Kr atom makes the beryllium bond weaken and the distant blue shift decrease. The nature and properties of beryllium bond have been analyzed with natural bond orbital (NBO), atoms in molecules (AIM), and energy decomposition., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The iron complexes CpFe(P(Ph)(2)N(Bn)(2))Cl (1-Cl), CpFe(P(Ph)(2)N(Ph)(2))Cl (2-Cl), and CpFe(P(Ph)(2)C(5))Cl (3-Cl)(where P(Ph)(2)N(Bn)(2) is 1,5-dibenzyl-1,5-diaza-3,7-diphenyl-3,7-diphosphacyclooctane, P(Ph)(2)N(Ph)(2) is 1,3,5,7-tetraphenyl-1,5-diaza-3,7-diphosphacyclooctane, and P(Ph)(2)C(5) is 1,4-diphenyl-1,4-diphosphacycloheptane) have been synthesized and characterized by NMR spectroscopy, electrochemical studies, and X-ray diffraction. These chloride derivatives are readily converted to the corresponding hydride complexes [CpFe(P(Ph)(2)N(Bn)(2))H (1-H), CpFe(P(Ph)(2)N(Ph)(2))H (2-H), CpFe(P(Ph)(2)C(5))H (3-H)] and H(2) complexes [CpFe(P(Ph)(2)N(Bn)(2))(H(2))]BAr(F)(4), [1-H(2)]BAr(F)(4), (where BAr(F)(4) is B[(3,5-(CF(3))(2)C(6)H(3))(4)](-)), [CpFe(P(Ph)(2)N(Ph)(2))(H(2))]BAr(F)(4), [2-H(2)]BAr(F)(4), and [CpFe(P(Ph)(2)C(5))(H(2))]BAr(F)(4), [3-H(2)]BAr(F)(4), as well as [CpFe(P(Ph)(2)N(Bn)(2))(CO)]BAr(F)(4), [1-CO]Cl. Structural studies are reported for [1-H(2)]BAr(F)(4), 1-H, 2-H, and [1-CO]Cl. The conformations adopted by the chelate rings of the P(Ph)(2)N(Bn)(2) ligand in the different complexes are determined by attractive or repulsive interactions between the sixth ligand of these pseudo-octahedral complexes and the pendant N atom of the ring adjacent to the sixth ligand. An example of an attractive interaction is the observation that the distance between the N atom of the pendant amine and the C atom of the coordinated CO ligand for [1-CO]BAr(F)(4) is 2.848 Å, considerably shorter than the sum of the van der Waals radii of N and C atoms. Studies of H/D exchange by the complexes [1-H(2)](+), [2-H(2)](+), and [3-H(2)](+) carried out using H(2) and D(2) indicate that the relatively rapid H/D exchange observed for [1-H(2)](+) and [2-H(2)](+) compared to [3-H(2)](+) is consistent with intramolecular heterolytic cleavage of H(2) mediated by the pendant amine. Computational studies indicate a low barrier for heterolytic cleavage of H(2). These mononuclear Fe(II) dihydrogen complexes containing pendant amines in the ligands mimic crucial features of the distal Fe site of the active site of the [FeFe]-hydrogenase required for H-H bond formation and cleavage., (© 2012 American Chemical Society)

p-Type Co(3)O(4) nanostructured films are synthesized by a plasma-assisted process and tested in the photocatalytic production of H(2) from water/ethanol solutions under both near-UV and solar irradiation. It is demonstrated that the introduction of fluorine into p-type Co(3)O(4) results in a remarkable performance improvement with respect to the corresponding undoped oxide, highlighting F-doped Co(3)O(4) films as highly promising systems for hydrogen generation. Notably, the obtained yields were among the best ever reported for similar semiconductor-based photocatalytic processes., (© 2011 American Chemical Society)

The cooperativity between hydrogen and halogen bonds in XY···HNC···XY (X, Y = F, Cl, Br) complexes was studied at the MP2/aug-cc-pVTZ level. Two hydrogen-bonded dimers, five hydrogen-bonded dimers, and ten trimers were obtained. The hydrogen- and halogen-bonded interaction energies in the trimers were larger than those in the dimers, indicating that both the hydrogen bonding interaction and the halogen bonding interaction are enhanced. The binary halogen bonding interaction plays the most important role in the ternary system. The hydrogen donor molecule influences the magnitude of the halogen bonding interaction much more than the hydrogen bonding interaction in the trimers with respect to the dimers. Our calculations are consistent with the conclusion that the stronger noncovalent interaction has a bigger effect on the weaker one. The variation in the vibrational frequency in the HNC molecule was considered. The NH antisymmetry vibration frequency has a blue shift, whereas the symmetry vibration frequency has a red shift. A dipole moment enhancement is observed upon formation of the trimers. The variation in topological properties at bond critical points was obtained using the atoms in molecules method, and was consistent with the results of the interaction energy analysis.

Hydrogen- and lithium-bonded complexes of A-H∕Li (A = F, Cl) with the amine analogues NF(3), NH(3), and NH(2)(CH(3)) were studied at the MP2∕6-311++G(d,p) level of theory. Bond extensions and redshifts were obtained for the H-bonded complexes, while bond extensions and blueshifts were obtained for the Li-bonded species. The variation of these and other properties with the basicity of the amines was investigated and rationalized by comparing the ab initio results with predictions from a model derived from perturbation theory.

A TiO₂/FTO (FTO=fluorine-doped tin oxide) electrode was prepared by dip-coating FTO in a suspension of TiO₂ prepared from a sol-gel method and was used as a photoanode to split an aqueous solution of formic acid to produce hydrogen. The surface of the TiO₂/FTO film was covered with assemblies of TiO₂ nanoparticles with a diameter of approximately 20 nm. Under irradiation by using a Xe lamp, splitting of formic acid was performed at different applied current densities. Compared to splitting water or utilizing FTO and Pt foil as the anode, the splitting voltage is much lower and can be as low as -0.27 V. The results show that the splitting voltage is related to the concentration of free formate groups. The evolution rate of hydrogen measured by using gas chromatography is 130 μmol h⁻¹ at a current density of 20 mA cm⁻² and the energy-conversion efficiency can be 1.79 %. Photoelectrolysis of formic acid has the potential to be an efficient way to produce hydrogen with a high energy-conversion efficiency., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Studies of a series of urea-based anion receptors designed to probe the potential for anion recognition through combinations of hydrogen and halogen bonding are presented. Proton- and fluorine-NMR spectroscopy indicates that the two interactions act in concert to achieve binding of certain anions, a conclusion supported by computational studies. Replacement of the halogen-bond donating iodine substituent by fluorine (which does not participate in halogen bonding) enables estimation of the contribution of this interaction to the free energy of anion binding. Evidence for attractive contacts between anions and electron-deficient arenes arising from the use of perfluoroarene-functionalized ureas as control receptors is also discussed. The magnitude of the free energy contribution of halogen bonding depends both on the geometric features of the group linking the hydrogen- and halogen-bond donor groups and on the identity of the bound anion. The results are interpreted in relation to fundamental features of the halogen-bonding interaction, including its directionality and unusual preference for halides over oxoanions. Cooperation between two distinct noncovalent interactions leads to unusual effects on receptor selectivity, a result of fundamental differences in the interactions of halogen- and hydrogen-bond donor groups with anions.

Carbon-fluorine bonds are the strongest known single bonds to carbon and as a consequence can prove very hard to cleave. Alhough vinyl and aryl C-F bonds can undergo oxidative addition to transition metal complexes, this reaction has appeared inoperable with aliphatic substrates. We report the addition of C(sp(3))-F bonds (including alkyl-F) to an iridium center via the initial, reversible cleavage of a C-H bond. These results suggest a distinct strategy for the development of catalysts and promoters to make and break C-F bonds, which are of strong interest in the context of both pharmaceutical and environmental chemistry.

Selected fluorinated and hydrogenated surfactants, namely a semifluorinated alkane (SFA): 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-henicosafluorononacosane (F10H19), two long chain alcohols: 18,18,18,17,17,16,16,15,15,14,14,13,13,12,12,11,11-heptadecafluorooctadecane-1-ol (F8H10OH) and octadecane-1-ol (C18OH) and with two long chain thiols of the analogous apolar part structure to the above-mentioned alcohols, i.e.: 18,18,18,17,17,16,16,15,15,14,14,13,13,12,12,11,11-heptadecafluorooctadecane-1-thiol (F8H10SH) and octadecane-1-thiol (C18SH) have been tested in mixtures with valinomycin as potential artificial matrixes for its immobilization. The thermodynamic analysis (DeltaG(exc)vsX(val) plots) based on surface pressure-area isotherm registration for particular valinomycin/surfactant mixtures, complemented with BAM images of the films structure indicate that only fluorinated surfactants are suitable materials for valinomycin incorporation as they form homogeneous miscible monolayers at X(val) below 0.5., (Copyright 2010 Elsevier B.V. All rights reserved.)

Ab initio calculations have been carried out to determine the structures, binding energies, and spin-spin coupling constants of complexes stabilized by X-Li...N bonds with F-Li, H-Li, and CH3Li as the Lewis acids. Complexes of these acids with the nitrogen bases N2, HCN, 1,3,5-triazine, pyrazine, 1,2,3-triazine, pyridine, and NH3 have linear X-Li...N bonds. Methylamine forms a nonlinear lithium bond only when F-Li is the lithium donor. Two bases, HN=CH2 and aziridine, form nonlinear X-Li...N bonds with each acid. Except for complexes with N2, which have small binding energies of about 5 kcal/mol, the binding energies of lithium-bonded complexes are appreciable, varying between 15 and 23 kcal/mol. The one-bond coupling constant 1J(F-Li) may increase or decrease upon complexation, but 1J(H-Li) and 1J(C-Li) decrease significantly. These coupling constants have their smallest values in complexes with nonlinear X-Li...N bonds. No correlations appear to exist between 1J(X-Li) and the X-Li distance and 1liJ(Li-N) and the Li-N distance. Values of the two-bond coupling constants 2liJ(X-N) are extremely small. Comparisons of 2liJ(F-N) with 2hJ(F-N) for coupling across a hydrogen bond and 2xJ(F-N) for coupling across a halogen bond suggest that the extremely small values of 2liJ(X-N) are not due to long X-N distances but to the low valence electron density on Li in lithium-bonded complexes.

CH(3)OX molecules (X = H, F, Cl and Br) can be formed in the atmosphere by the CH(3) + OX and CH(3)O + X recombination reactions. In the present study the results of a theoretical analysis of the kinetics and thermochemistry of this class of reactions are presented. The molecular properties of the reactants and products were derived from ab initio calculations. The high-pressure limiting rate constants for the recombination reactions were evaluated using a version of the statistical adiabatic channel model. The kinetic equations derived in this study allow a description of the kinetics of the reactions under investigation in the temperature range of 200-500 K.

We examined the effect of hydrogen content in various polymers in a N2/H2 discharge for surface amine functionalization. Three polymers (polyethylene (PE), polyvinylidene fluoride (PVDF), and poly(tetrafluoroethylene) (PTFE)) containing various amounts of hydrogen and fluorine were treated with an atmospheric pressure dielectric barrier discharge (DBD). While surface modification was observed on the PE and the PVDF in a pure N2 discharge, adding H2 in a N2 discharge was necessary to observe the fluorine etching on the surface of the PVDF and PTFE polymers. The presence of a slight amount of hydrogen in the gas mixture was also a prerequisite to the formation of amino groups on the surface of all three polymers (max NH2/C approximately 5%). Aging revealed that the modified polymer surfaces treated in a N2-H2 discharge were less prone to hydrophobic recovery than were surfaces treated in pure N2, due primarily to the presence of a higher density of polar groups on the surfaces. We demonstrated that H atoms in the discharge are necessary for the surface amine functionalization of polymers in a N2 atmospheric pressure DBD, regardless of polymer chemical composition. It is therefore possible to control the plasma functionalization process and to optimize the concentration and specificity of NH2 grafted onto polymer surfaces by varying the H2 concentration in a N2 atmospheric pressure DBD.

A selection of mono- and pseudo ortho di-substituted octafluoro[2.2]paracyclophane derivatives were analyzed using (19)F-(1)H HOESY, (1)H COSY and (19)F COSY techniques. This resulted in the unambiguous assignment of the (19)F and (1)H NMR resonances, and also revealed interesting solvent effects and noteworthy coupling patterns for various J(HH), J(HF), and J(FF) interactions, including observable through bond (7)J(FF) and (8)J(FF) couplings. For the four mono-substituted derivatives, the assignments were achieved through the combination of (19)F-(1)H HOESY, (1)H COSY and (19)F COSY techniques. The C(2) symmetry of the six pseudo ortho di-substituted derivatives that were examined produced simplified spectra, and careful inspection of the characteristic (1)H coupling patterns led to the assignment of (1)H signals. Therefore only (19)F-(1)H HOESY experiments were required to complete the assignments for those molecules. Refinements and alternative strategies for previous protocols are presented for the molecules that were less responsive to nuclear Overhauser effect (nOe) experiments., (Copyright (c) 2009 John Wiley & Sons, Ltd.)

An examination of strong hydrogen bonds found in (ROH)(n)...FHF(-) clusters (n = 1 and 2; R = H, CH(3), C(2)H(5)) is presented. Excellent agreement is observed between thermochemical values obtained from high-pressure mass spectrometric measurements and those predicted from MP2(full)/6-311++G(d,p)//B3LYP/6-311++G(d,p) calculations. Calculated structures are examined, and insight into the geometric nature of the bonding for these systems is obtained. In the case of water binding to FHF(-), it was found that the large entropic advantage of one particular structure, which was not the most enthalpically favored, was significant enough to make it the predominant species within the ion source. In the case of methanol solvation, no evidence of secondary interaction of the methyl group and any other moiety could be found. The structural details revealed from calculations of the ethanol-solvated clusters indicate that secondary interactions between the terminal methyl group and FHF(-) have an impact on the length of the FHF and OHF bonds.

The reaction of (PEt(3))(2)Ni(eta(2)-C(14)H(10)), a source of the reactive Ni(PEt(3))(2) moiety, with 1,2,4,5-F(4)C(6)H(2) yields a mixture of three C-F bond activation products that include the unexpected products (PEt(3))(2)NiF-2,3,5,6-F(4)C(6)H and (PEt(3))(2)NiF-2,3,5-F(3)C(6)H(2). Monitoring the reaction mixture via (19)F and (1)H NMR also reveals the presence of the C-H bond activation product, (PEt(3))(2)NiH-2,3,5,6-F(4)C(6)H which is produced in a rapid equilibrium reaction. This observation provides insight into the steps necessary to modify nickel complexes for selective C-F bond activation in a variety of polyfluorinated aromatic substrates, but also expands the potential of simple nickel compounds for C-H bond activation and functionalization reactions.