Extent Of Fluorination Research Articles

Biodegradation of Amphipathic Fluorinated Peptides Reveals a New Bacterial Defluorinating Activity and a New Source of Natural Organofluorine Compounds.

Three peptides comprising mono-, di-, and tri-fluoroethylglycine (MfeGly, DfeGly, and TfeGly) residues alternating with lysine were digested by readily available proteases (elastase, bromelain, trypsin, and proteinase K). The degree of degradation depended on the enzyme employed and the extent of fluorination. Incubation of the peptides with a microbial consortium from garden soil resulted in degradation, yielding fluoride ions. Further biodegradation studies conducted with the individual fluorinated amino acids demonstrated that the degree of defluorination followed the sequence MfeGly > DfeGly > TfeGly. Enrichment of the soil bacteria employing MfeGly as a sole carbon and energy source resulted in the isolation of a bacterium, which was identified as Serratia liquefaciens. Cell-free extracts of this bacterium enzymatically defluorinated MfeGly, yielding fluoride ion and homoserine. In silico analysis of the genome revealed the presence of a gene that putatively codes for a dehalogenase. However, the low overall homology to known enzymes suggests a potentially new hydrolase that can degrade monofluorinated compounds. 19F NMR analysis of aqueous soil extracts revealed the unexpected presence of trifluoroacetate, fluoride ion, and fluoroacetate. Growth of the soil consortium in tryptone soya broth supplemented with fluoride ions resulted in fluoroacetate production; thus, bacteria in the soil produce and degrade organofluorine compounds.

Dramatic Enhancement of Rare-Earth Metal–Organic Framework Stability Via Metal Cluster Fluorination

Rare-earth polynuclear metal–organic frameworks (RE-MOFs) have demonstrated high durability for caustic acid gas adsorption and separation based on gas adsorption to the metal clusters. The metal clusters in the RE-MOFs traditionally contain RE metals bound by μ3–OH groups connected via organic linkers. Recent studies have suggested that these hydroxyl groups could be replaced by fluorine atoms during synthesis that includes a fluorine-containing modulator. Here, a combined modeling and experimental study was undertaken to elucidate the role of metal cluster fluorination on the thermodynamic stability, structure, and gas adsorption properties of RE-MOFs. Through systematic density-functional theory calculations, fluorinated clusters were found to be thermodynamically more stable than hydroxylated clusters by up to 8–16 kJ/mol per atom for 100% fluorination. The extent of fluorination in the metal clusters was validated through a 19F NMR characterization of 2,5-dihydroxyterepthalic acid (Y-DOBDC) MOF synthesized with a fluorine-containing modulator. 19F magic-angle spinning NMR identified two primary peaks in the isotropic chemical shift (δiso) spectra located at −64.2 and −69.6 ppm, matching calculated 19F NMR δiso peaks at −63.0 and −70.0 ppm for fluorinated systems. Calculations also indicate that fluorination of the Y-DOBDC MOF had negligible effects on the acid gas (SO2, NO2, H2O) binding energies, which decreased by only ∼4 kJ/mol for the 100% fluorinated structure relative to the hydroxylated structure. Additionally, fluorination did not change the relative gas binding strengths (SO2 > H2O > NO2). Therefore, for the first time the presence of fluorine in the metal clusters was found to significantly stabilize RE-MOFs without changing their acid-gas adsorption properties.

Multi-functionalized fluorinated graphene composite coating for achieving durable electronics: Ultralow corrosion rate and high electrical insulating passivation

Graphene is regarded as the best anticorrosion material; however, due to its inherent electrical conductivity, it, instead, greatly promotes galvanic corrosion when added as a filler above a certain loading threshold in a polymer composite coating. Electrically insulating 2D materials such as hexagonal boron nitride (h-BN), which could be alternatives, also fail due to their poor dispersibility/compatibility with the polymer matrix, thus limiting their practical applications. Herein, we report a unique fluorinated graphene (FG), with optimizable F/C and C/O ratios (versatile surface chemistry properties), produced by scalable fluorination of facile and eco-friendly electrochemically exfoliated graphene (ECG, surface properties of which are tunable by varying electrochemical conditions) and propose a one-step and cost-effective fluorination route towards highly polymer matrix compatible composite for electronic passivation; in fact this alloys two steps optimization of surface functionalities leading to required properties of FG and the composite. By tuning and understanding their hydrophobicity, electrical conductivity, extent of fluorination, etc., through molecular dynamics (MD) simulations as well, with just 1% filler loading, the FG-polymer-composite shows the superior anticorrosion performance (corrosion rate (CR) = 7.83 × 10−8 mm/year; current = 3.37 × 10−12 A cm−2). Construction of a robust diffusion barrier indicated by a monotonic decrease in CR with FG loading leads FG to outperform other reported functionalized graphene and BN-related 2D materials. Extension of the use of FG composites to a nonmetallic substrate such as a flexible printed circuit board (PCB) is an original idea, and superior corrosion inhibition is achieved while preventing the risk of electrical short circuits due to the electrical insulating nature and the high breakdown voltage of FG; thus, making it a durable passivation layer on electronic devices, even in harsh environments. This work represents a breakthrough in anticorrosion technology and provides a novel strategy for exploring extremely impermeable composites for the long-term passivation of multi-functionalized electronics.

Systematic and non-systematic substituent effects gleaned from studies on CuTCNQFn (n = 0, 1, 2, 4): Electrocrystallisation and characterisation of CuTCNQF

Exploitation of ligand substituent effects provides a method for systematically tuning the properties of inorganic compounds. Thus, fluorination of TCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) followed by reduction to their anionic and dianionic forms allows a series of copper(I) coordination polymers to be prepared that vary systematically with respect to redox and other properties. However, the catalytic properties of CuTCNQFn (n = 0, 1, 2, 4) do not vary systematically with the extent of fluorination as revealed by combining data obtained in this study using TCNQF and TCNQF2 with that published with TCNQ and TCNQF4. Initial studies confirmed that the cyclic voltammetry of 8.0 mM TCNQF0 (TCNQF0 = 2-fluoro-7,7,8,8-tetracyanoquinodimethane) displays two ideal one-electron reversible diffusion controlled TCNQF0/1− and TCNQF1−/2− processes at a glassy carbon electrode in acetonitrile (0.1 M Bu4NPF6). Upon introduction of equimolar [Cu(MeCN)4]+, a series of new processes involving oxidation and reduction of surface confined electrocrystallised Cu+-TCNQF1− as well as a Cu+-TCNQF2− derivative were detected. Mechanisms for the electrocrystallisation of kinetically and thermodynamically favoured phases of CuTCNQF are proposed. Variable morphology of elecrocrystallised TCNQF-based material onto ITO electrodes was evident from SEM images. CuTCNQF in the thermodynamically favoured phase was also synthesised chemically by reaction of TCNQF with copper(I) iodide or copper foil or via the reaction between TCNQF1− generated by bulk electrolysis in MeCN (0.10 M Bu4NPF6 and a stoichiometric amount of [Cu(MeCN)4]+. The catalytic activity of CuTCNQF and CuTCNQF2, formed on the surface of a copper foil, with respect to the [Fe(CN)6]3−/S2O32− aqueous redox reaction was investigated by analysis of spectrophotometric and open circuit potential measurements. Comparison with published data with CuTCNQ-Cu foil and CuTCNQF4-Cu foil revealed that the extent of catalysis achieved in these materials were similar and slow. In contrast, reaction rates in the presence of the CuTCNQF2 and CuTCNQF4-Cu foil analogues were much faster, but also similar to each other. This non-systematic effect implies that catalysis requires the TCNQ(Fn)2− (reduced dianion) to be accessible, thus the reversible potential for neither the Cu-TCNQFn1−/2− (n = 0, 1) are sufficient to achieve substantial catalysis while the reversible potential for both the Cu-TCNQFn1−/2− (n = 2, 4) reactions are well in excess of the minimum value required to achieve catalysis. The conductivity of CuTCNQF was 1.86 × 10−5 S cm−1 which is at the low end of the semiconductor range, and hence orders of magnitude less than for the kinetically favoured phase of CuTCNQ; 0.2 S cm−1. Interestingly, the fluorinated analogues of the readily accessible, highly conducting (kinetically favoured) CuTCNQ phase I are only detected transiently under voltammetric conditions for CuTCNQFn (n = 1, 2) and have not been detected for the CuTCNQF4 derivative.

Synthesis and Crystal Structures of Volatile Neptunium(IV) β-Diketonates.

Production of certified reference materials in support of domestic nuclear forensics programs require volatile precursors for introduction into electromagnetic isotopic separation instruments. β-Diketone chelates of tetravalent actinides are known for their high volatility, but previously developed synthetic approaches require starting material (NpCl4) that is prohibitively difficult and hazardous to prepare. An alternative strategy was developed here that uses controlled potential electrolysis to reduce neptunium to the tetravalent state in submolar concentrations of hydrochloric acid. Four different β-diketone ligands of varying degrees of fluorination were reacted with an aqueous solution of Np4+. Products of this reaction were characterized via X-ray diffraction and infrared spectroscopy, and were found to be neutral 8-coordinate complexes that adopt square antiprismatic crystal geometry. Synthesis of Np β-diketonates by this approach circumvents the necessity of using NpCl4 in tetravalent Np coordination compound synthesis. The volatility of the complexes was assessed using thermogravimetric analysis, where the temperature of sublimation was determined to be in the range of 180° to 205 °C. The extent of fluorination did not appreciably alter the sublimation temperature of the complex. Thermal decomposition of these compounds was not observed during sublimation. High volatility and thermal stability of Np β-diketonates make them ideal candidates for gaseous introduction into isotopic separation instruments.

Controlled radical fluorination of poly(meth)acrylic acids in aqueous solution

Fluorinated alkenes exhibit very poor reactivity in copolymerization with non-fluorinated polar monomers such as acrylates. Herein we describe a convenient method for the synthesis of poly(vinyl fluoride-co-acrylic acid) and poly(2-fluoropropene-co-methacrylic acid) copolymers. Thus, the silver-catalyzed decarboxylative radical fluorination of poly(acrylic acid) with Selectfluor in water at room temperature affords poly(vinyl fluoride-co-acrylic acid) copolymers in high yields with well-defined molecular weights and polydispersities. A linear correlation is observed between the extent of fluorination and the amount of Selectfluor, indicating that the copolymer of virtually any monomer ratio can be readily accessed by controlling the amount of Selectfluor. This controlled decarboxylative fluorination is extended to poly(methacrylic acid), leading to well-defined poly(2-fluoropropene-co-methacrylic acid) copolymers.

Optimal extent of fluorination enabling strong temperature-dependent aggregation, favorable blend morphology and high-efficiency polymer solar cells

Temperature-dependent aggregation is a key property for some donor polymers to realize favorable bulk-heterojunction (BHJ) morphologies and high-efficiency (>10%) polymer solar cells. Previous studies find that an important structural feature that enables such temperature-dependent aggregation property is the 2nd position branched alkyl chains sitting between two thiophene units. In this report, we demonstrate that an optimal extent of fluorination on the polymer backbone is a second essential structural feature that enables the strong temperature-dependent aggregation property. We compare the properties of three structurally similar polymers with 0, 2 or 4 fluorine substitutions in each repeating unit through an in-depth morphological study. We show that the non-fluorinated polymer does not aggregate in solution (0.02 mg mL−1 in chlorobenzene) at room temperature, which results in poor polymer crystallinity and extremely large polymer domains. On the other hand, the polymer with four fluorine atoms in each repeating unit exhibits an excessively strong tendency to aggregate, which makes it difficult to process and causes a large domain. Only the polymer with two fluorine atoms in each repeating unit exhibits a suitable extent of temperature-dependent aggregation property. As a result, its blend film achieves a favorable morphology and high power conversion efficiency. This provides another key design rationale for developing donor polymers with suitable temperature-dependent aggregation properties and thus high performance.

Sol–Gel Chemistry of Titanium Alkoxide toward HF: Impacts of Reaction Parameters

The sol–gel chemistry of titanium-based oxide prepared in a fluorinated medium leads to an oxy-hydroxyfluorinated framework owing to the occurrence of both hydrolysis and fluorolysis reactions. Here, a systematic study was carried out to investigate the impact of the sol–gel synthesis parameters on the reaction of titanium alkoxides and HF. This study provides comprehensive insights into the sol–gel process in a fluorinated medium. Depending on the extent of fluorination, two types of structures can be stabilized including an anatase Ti1–x–y□x+yO2–4(x+y)F4x(OH)4y and a fluoride-rich hexagonal-tungsten-bronze (HTB) Ti1–x□xO1–4x(F,OH)2+4x phases, where □ refers to titanium vacancies. The reactivity of titanium alkoxide in alcohol toward HF has been shown to mostly depend on the solvent characteristics highlighting an alcohol interchange reaction between the titanium precursor and the solvent. Increasing the fluorine concentration leads to a structural change from the anatase to the fluoride-rich HTB phase, ...

Photothermally controlled structural switching in fluorinated polyene-graphene hybrids.

Fluorination of graphene enables tuning of its electronic properties, provided that control of the fluorination degree and of modification of graphene structure can be achieved. In this work we demonstrate that SF6 modulated plasma fluorination of monolayer graphene yields polyene-graphene hybrids. The extent of fluorination is determined by the plasma exposure time and controlled in real time by monitoring the change in the optical response by spectroscopic ellipsometry. Raman spectroscopy reveals the formation of polyenes in partially fluorinated graphene (F/C < 0.25), which are responsible for changes in conductivity and for opening a transport gap of ∼25 meV. We demonstrate that the cis- and trans-isomers of the polyenes in graphene are tunable using the photothermal switching. Specifically, the room temperature fluorination results in the cis-isomer that can be converted to the trans-isomer by annealing at T > 150 °C, whereas photoirradiation activates the trans-to-cis isomerization. The two isomers give to the polyene-graphene hybrids different optical and conductivity properties providing a way to engineer electrical response of graphene.

Novel Acid-Activated Fluorophores Reveal a Dynamic Wave of Protons in the Intestine of Caenorhabditis elegans

Unlike the digestive systems of vertebrate animals, the lumen of the alimentary canal of Caenorhabditis elegans is unsegmented and weakly acidic (pH ~4.4), with ultradian fluctuations to pH > 6 every 45-50 s. To probe the dynamics of this acidity, we synthesized novel acid-activated fluorophores termed Kansas Reds. These dicationic derivatives of rhodamine B become concentrated in the lumen of the intestine of living C. elegans and exhibit tunable pKa values (2.3-5.4), controlled by the extent of fluorination of an alkylamine substituent, that allow imaging of a range of acidic fluids in vivo. Fluorescence video microscopy of animals freely feeding on these fluorophores revealed that acidity in the C. elegans intestine is discontinuous; the posterior intestine contains a large acidic segment flanked by a smaller region of higher pH at the posterior-most end. Remarkably, during the defecation motor program, this hot spot of acidity rapidly moves from the posterior intestine to the anterior-most intestine where it becomes localized for up to 7 s every 45-50 s. Studies of pH-insensitive and base-activated fluorophores as well as mutant and transgenic animals revealed that this dynamic wave of acidity requires the proton exchanger PBO-4, does not involve substantial movement of fluid, and likely involves the sequential activation of proton transporters on the apical surface of intestinal cells. Lacking a specific organ that sequesters low pH, C. elegans compartmentalizes acidity by producing of a dynamic hot spot of protons that rhythmically migrates from the posterior to anterior intestine.

Interaction of trifluoromethane (CHF3) with alkali hydroxides and carbonates

Heterogeneous reactions of trifluoromethane (CHF3) with solid alkali hydroxides and carbonates were investigated under static and dynamic conditions and at moderate temperatures. In all cases, main reaction is fluorination characterised by a complete decomposition (mineralisation) of the fluorinating agent, CHF3, and the formation of solid metal fluorides, CO, and H2O. Under specific conditions, CO and H2O may react further through the water–gas shift reaction and form solid metal carbonate. Extent of fluorination strongly depends on temperature and is dictated by the nature of the solid precursor. Alkali hydroxides, KOH, NaOH, and LiOH, are the most reactive solids that start to react with CHF3 at relatively low temperatures, 370–484K. Onset temperatures for fluorination of corresponding carbonates are 100–150K higher. Reactivity of the solids towards CHF3 can be correlated with their basicity. Reactions are rationalised on the basis of an acid–base type of interactions between CHF3 as a very weak CH acid and the very strong basic oxygen species in the solids. These interactions apparently play a decisive role during the initial binding of CHF3 molecule to the solid reactant, in this way enabling or facilitating other decomposition steps that finally lead to a complete destruction of the CHF3 molecule. Total decomposition of CHF3 with KOH or NaOH, achievable at relatively very low temperatures, could in some specific cases represent a possible alternative to the energy-demanding CHF3 decomposition by incineration.

Factors Affecting the Spontaneous Motion of Condensate Drops on Superhydrophobic Copper Surfaces

The coalescence-induced condensate drop motion on some superhydrophobic surfaces (SHSs) has attracted increasing attention because of its potential applications in sustained dropwise condensation, water collection, anti-icing, and anticorrosion. However, an investigation of the mechanism of such self-propelled motion including the factors for designing such SHSs is still limited. In this article, we fabricated a series of superhydrophobic copper surfaces with nanoribbon structures using wet chemical oxidation followed by fluorization treatment. We then systematically studied the influence of surface roughness and the chemical properties of as-prepared surfaces on the spontaneous motion of condensate drops. We quantified the "frequency" of the condensate drop motion based on microscopic sequential images and showed that the trend of this frequency varied with the nanoribbon structure and extent of fluorination. More obvious spontaneous condensate drop motion was observed on surfaces with a higher extent of fluorization and nanostructures possessing sufficiently narrow spacing and higher perpendicularity. We attribute this enhanced drop mobility to the stable Cassie state of condensate drops in the dynamic dropwise condensation process that is determined by the nanoscale morphology and local surface energy.

Effect of Fluorination on the Surface Properties of Titania P25 Powder: An FTIR Study

A study was carried out on the consequences of the -OH(surf)/F(-) exchange occurring at the surface of TiO(2) P25 when suspended in HF/F(-) solutions. The maximum extent of fluorination was reached at pH 3.0, resulting in the fixation on the surface of ca. 2.5 F(-)/nm(2). The surface features of fluorinated samples under two selected conditions were investigated by IR spectroscopy, in comparison with pristine TiO(2). The collected data suggested that bridged -OH(surf), likely located on regular facets, was more resistant to exchange with F(-). Combined high resolution transmission electron microscopy (HRTEM), inductively coupled plasma mass spectrometry (ICP-MS) and IR measurements indicated that the fluorination performed in the adopted condition did not induce any etching of TiO(2) particles, and the -OH(surf)/F(-) exchange appeared reversible by treatment in concentrated basic solutions. Furthermore, fluorination resulted in an increase of the Lewis acid strength of surface Ti(4+) sites, which, as a consequence, retained adsorbed water molecules even after outgassing at 423 K. Such an effect involved the overwhelming majority of cations exposed on regular facets.

Electronic structure of self-assembled (fluoro)methylthiol monolayers on the Au(1 1 1) surface: Impact of fluorination and coverage density

We report the results of a density-functional theory study on a series of metal/organic interfaces consisting of self-assembled monolayers (SAMs) of methylthiol and mono-, di-, and tri-fluoromethylthiols, chemisorbed on the Au(1 1 1) surface. The effects of coverage density and extent of fluorination are examined. Both are found to strongly impact: (i) the component of the SAM dipole moment perpendicular to the surface; (ii) the SAM-induced work-function modification of the gold surface; and (iii) the energy-level alignments of both the highest occupied molecular levels and the molecular-signature states of the SAM with respect to the Fermi level of gold and, as a result, the ionization potential of the SAM when deposited on gold. Saturations of the effects are observed at the higher levels of fluorination and coverage.

Adsorption of hexane and benzene on fluorinated silicas: The effect of the perfluoralkyl chain length

By means of the gas chromatography and a static adsorption method, the extent of fluorination of the carrier surface, determined by the length of the grafted radical chain, affects the adsorption properties of silicas with perfluorohexyl, perfluoropropyl, and trifluoromethyl coatings. The analysis of data on the original carrier and chemically hydrophobized silicas, including a sample with grafted octyl groups used as the reference, shows that modification leads to the decrease in both the adsorption (a at 298 K and the Henry constants (K H ) in a wide temperature range for hexane and benzene. However, in contrast to silicas with perfluoropropyl or perfluorohexyl coatings, the a and K H values on trifluorometylsilica became equal (n-alkanes) or even somewhat lower (aromatic hydrocarbons) than those observed on the non-polar octylsilica surface. Irrespective of the degree of fluorination of the silica surface, the substitution and screening of silanol groups in silica lead to weakening the polarity of polyfluoroalkylsilicas as compared with the original carrier.

Induction and Enhancement of Ferroelectric Smectic C* Phase in Multi-Component Room Temperature Mixtures

Six multi-component room-temperature ferroelectric liquid crystal (FLC) mixtures have been formulated and investigated using optical polarizing microscopy, dielectric spectroscopy as well as electro-optic methods. In all the mixtures smectic C* phase is either induced or enhanced. Effect of various dopants on the occurrence and thermal stability of different phases has been discussed. Spontaneous polarizations, measured as a function of temperature by reversal current method, are found to vary between 13–62 nC/cm2 at room temperature in all the mixtures. Different types of dielectric absorption behavior were observed in planar geometry of the FLC cells. Critical frequencies of Goldstone and soft modes have been determined by frequency dependent dielectric study. Rigidity of the core structure, nature of chirality and extent of fluorination of the constituent molecules are found to have pronounced effect on the collective mode relaxation behavior of the mixtures.

Effect of the Partial Hydrogenation of Hydrophobic Chains on the Mixing of Fluoroalkanols in an Adsorbed Film at the Hexane/Water Interface

The mixed adsorbed film of 1H,1H-perfluorooctanol (DFC8OH) and 1H,1H,2H,2H-perfluorodecanol (TFC10OH) at the hexane/water interface was studied on the basis of interfacial tension measurement and its thermodynamic data analysis. An adsorbed film at any composition of the mixed system as well as those of pure DFC8OH and TFC10OH systems exhibits three states: the gaseous, expanded, and condensed states. Construction of the phase diagram of adsorption clarified that DFC8OH and TFC10OH mix almost ideally in the gaseous and expanded states. On the contrary, the excess Gibbs energy of adsorption gH,E value evaluated in the condensed state was positive. These results are explained by considering the following two factors: (1) The mixing of binary alcohols is accompanied by the loss of dispersion interaction energy due to the difference in extent of fluorination of hydrophobic chains and in their chain length and increases the gH,E value. (2) Since the interchange energy concerning the interaction between dipoles with different dipole moments is negative, the mixing of these alcohols reduces the repulsive force between hydrophilic groups and thus leads to a decrease in the gH,E value. In the gaseous and expanded states, both of above two factors are not effective. On the other hand, the positive gH,E value in the condensed state is attributable to more effective dispersion interaction than the dipole−dipole interaction in short molecular distance, and so factor 1 becomes dominant. Comparison of the gH,E value of the present system with that of the homologous TFC10OH−TFC12OH mixture leads us to a conclusion that the hydrogenation on β-carbons in hydrophobic chains affects appreciably the balance of interactions between hydrophilic and hydrophobic groups which governs the mixing of molecules in adsorbed films.

Solid-State NMR Analysis of Fluorinated Single-Walled Carbon Nanotubes: Assessing the Extent of Fluorination

Fluorinated single-walled carbon nanotubes (F-SWNTs) have been characterized by magic angle spinning 13C NMR spectroscopy and the results correlated with Raman, IR, and X-ray photoelectron spectroscopy measurements. The 13C NMR shift for the sp3 fluorine-substituted (CF) carbon atoms of the SWNT sidewall is observed at δ = 83.5 ppm. This apparently unusual shift compared to those of most other tertiary alkyl fluorides is confirmed to be due to the CF moieties from ab initio calculations on an 80-carbon fragment of the 5,5 (armchair) SWNT and is in good agreement with the predominance of 1,2-addition rather than 1,4-addition of fluorine. The lack of observable scalar 13C−19F coupling for the CF carbon signal over a wide range of spinning speeds and at two different field strengths apparently results from interaction between 19F−19F and 13C−19F dipolar couplings and from magnetization exchange between the 13C doublet components caused by fluorine spin diffusion. The assignment of the 83.5 ppm peak is furthe...

Synthesis and Characterization of Novel Fluorinated Poly(oxomolybdates).

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Synthesis and Characterization of Novel Fluorinated Poly(oxomolybdates)

Two novel poly(oxofluoromolybdate) clusters, [Mo6O18F6]6- and [Mo7O22F3]5-, have emerged from systematic field studies on the hydrothermal fluorination of poly(oxometalates). They are accessible via the hydrothermal treatment of Mo(VI)-based precursors in the presence of MF additives (M = Li, Na, Cs, NMe4). The new fluorinated polyanions are stabilized by specific alkali-cation combinations, and their packing motifs can be tuned through the careful choice of cations and synthetic parameters. The [Mo6O18F6]6- anion can be described as a cored and fluorinated form of the Anderson-Evans cluster type. It is stabilized by the interaction of two alkali cations with the fluorinated faces of the ring-shaped anion. The partial replacement of these capping alkali cations by the bulky, organic NMe4(+) cation leads to the formation of [Mo7O22F3](5-)-based compounds. Thus, the extent of fluorination can be controlled through the polarizability of the cationic environment: in the [Mo7O22F3]5- anion, half of the fluoride atoms of the [Mo6O18F6]6- anion are replaced by a capping MoO4 tetrahedron, thereby rendering this anion a fluorinated, lacunar derivative of the alpha-[Mo8O26]4- octamolybdate anion. All compounds have been structurally characterized by single-crystal X-ray diffraction and solid-state NMR spectroscopy. The templating role of the alkali cations is discussed and explained with the help of electrostatic calculations.