SF5 Group Research Articles

Green Phosphorescence and Electroluminescence of Sulfur Pentafluoride-Functionalized Cationic Iridium(III) Complexes.

We report on four cationic iridium(III) complexes [Ir(C^N)2(dtBubpy)](PF6) that have sulfur pentafluoride-modified 1-phenylpyrazole and 2-phenylpyridine cyclometalating (C^N) ligands (dtBubpy = 4,4'-di-tert-butyl-2,2'-bipyridyl). Three of the complexes were characterized by single-crystal X-ray structure analysis. In cyclic voltammetry, the complexes undergo reversible oxidation of iridium(III) and irreversible reduction of the SF5 group. They emit bright green phosphorescence in acetonitrile solution and in thin films at room temperature, with emission maxima in the range of 482-519 nm and photoluminescence quantum yields of up to 79%. The electron-withdrawing sulfur pentafluoride group on the cyclometalating ligands increases the oxidation potential and the redox gap and blue-shifts the phosphorescence of the iridium complexes more so than the commonly employed fluoro and trifluoromethyl groups. The irreversible reduction of the SF5 group may be a problem in organic electronics; for example, the complexes do not exhibit electroluminescence in light-emitting electrochemical cells (LEECs). Nevertheless, the complexes exhibit green to yellow-green electroluminescence in doped multilayer organic light-emitting diodes (OLEDs) with emission maxima ranging from 501 nm to 520 nm and with an external quantum efficiency (EQE) of up to 1.7% in solution-processed devices.

Synthesis and Property of Novel Phthalocyanine Having Pentafluorosulfanyl (SF5) Group on the Peripheral Positions

The pentafluorosulfanyl (SF5) group is probably one of the most obscure, but attractive fluorinated functional groups in future materials. The SF5 moiety is thermally, hydrolytically and chemically stable and is considered to be a “super-trifluoromethyl (CF3) group”. Besides, the SF5 group is larger than the CF3 group with higher lipophilicity and electronegativity. In addition, the geometry of these two functional groups is completely different: the SF5 group presents a pyramidal electron density while the CF3 displays an inverted cone of density. Although applications of SF5 compounds in material science and medicinal chemistry have been reported, there is no example of the synthesis of phtalocyanineshaving an SF5 moiety in their structures. In this paper, we disclose the synthesis and properties of SF5-substituted phtalocyanines.

Synthesis of SF5-Substituted Tetrapyrroles, Metalloporphyrins, BODIPYs, and Their Dipyrrane Precursors.

The synthesis of novel pentafluorosulfanyl (SF5)-substituted A4-type porphyrins, their corresponding Zn(II)- and Pd(II)-metal complexes, A3-, A2B- and AB2-type corroles, BODIPYs, and their dipyrrane precursors was studied utilizing commercially available SF5-substituted aryl aldehydes. In addition, the functionalization of SF5-substituted tetrapyrroles was investigated by applying the concept of the nucleophilic aromatic substitution (S(N)Ar) with alcohols and sodium azide onto the pentafluorophenyl moiety of a trans-A2B2-porphyrin and two corrole derivatives with a mixed substitution pattern involving the SF5 group. This allows a fine-tuning of the properties of these macrocycles through a selective and mild introduction of functional groups, giving access to multifunctionalized SF5-substituted porphyrinoids. As an example, one functionalized corrole was further reacted with an azido-substituted BODIPY via the copper(I)-catalyzed 1,3-dipolar cycloaddition yielding the first corrole-BODIPY heterodimer involving the pentafluorosulfanyl group.

Pentafluorosulfanyl (SF5) in dyes: C3-Regioselective synthesis of α-mono-substituted subphthalocyanine with SF5-phenyl group

Pentafluorosulfanyl (SF5) is a unique fluorinated functional group. It has high lipophilicity and electronegativity, and is chemically and thermally stable. In addition, the steric hindrance of SF5 is larger than that of the trifluoromethyl (CF3) group. Therefore the introduction of SF5 group into functional dyes such as phthalocyanines and subphthalocyanines should be an attractive strategy to improve their robustness and alter their optical property. We attempted the C3-regioselective cyclotrimerization of aryl-substituted phthalonitriles 3 to provide subphthalocyanines (SubPcs) 1. α-Mono-substituted SubPc 1a was C3-regioselectively synthesized by introducing a bis(SF5)Ph group on the α-peripheral position providing 1a as a single isomer. The effect of the SF5 group on the synthesis and optical property of SubPcs were investigated by comparing with the H and CF3 analogues, 1b and 1c.

Theoretical studies on energetic materials bearing pentaflurosulphyl (SF 5 ) groups

Heats of formation (HOF) for a series of energetic materials containing SF5 group were studied by density functional theory. Results show that HOFs increase with the augmention of field effects of substituted groups. Addition of furazan or furoxan ring increases HOF of the energetic materials. All the SF5-containing compounds have densities which are ∼0.19 g/cm3 higher than those containing –NH2 group. S–F bond is the trigger bond for the thermolysis process in the title compounds and bond dissociation energies of the weakest bonds range from 351.1 to 388.3 kJ/mol. Detonation velocities (D) and pressures (P) are evaluated by Kamlet–Jacobs equations with the calculated densities and HOFs. Results show that increasing the amount of furazan rings results in a larger D and P. Considering the detonation performance and thermal stability, eight compounds may be considered as potential candidates for high-energy density materials. SF5 group is an important energetic group. Considering the importance of the SF5 group, a series of energetic materials containing SF5 group were investigated to discuss the HOF, BDE and detonation properties in order to search for compounds with better performance.

The pentafluorosulfanyl group in cannabinoid receptor ligands: synthesis and comparison with trifluoromethyl and tert-butyl analogues

Competitive CB1 receptor antagonists carrying an aromatic SF5 group in position 3 of a pyrazole ring were synthesised and compared with their CF3 and tert-butyl analogues. Results confirmed that an aromatic SF5 group can be used as a bioisosteric analogue of a CF3 group and possibly of a bulky aliphatic group too.

Synthesis and pKa values of 2-(3- and 4-pentafluorosulfanylphenyl)-2-fluorocyclopropylamines

Starting from 3- and 4-pentafluorosulfanylbenzaldehydes, a series of cis- and trans-2-aryl-2-fluorocyclopropylamines bearing an SF5 group in 3- or 4-position of the aryl ring were synthesized in 7 steps via the corresponding cyclopropanecarboxylic acids. While the pKa values of the carboxylic acids are very little depending on the stereochemistry at the cyclopropane ring and the regiochemistry of the SF5-substituents in the aryl ring, the pKa of the corresponding 2-fluorocyclopropylamines is strongly dependent on the stereochemistry at the three-membered ring due to hyperconjugative effects of the CF and the CN bonds. Again, the regiochemistry of SF5 substitution in the phenyl ring has almost no influence.

ChemInform Abstract: Preparations and Reactions of SF5‐Substituted Aryl and Heteroaryl Derivatives via Mg and Zn Organometallics.

AbstractOrganometallic protocols, compatible with the sensitive ‐SF5 group are exploited for the preparation of a variety of SF5‐substituted aryl and heteroaryl derivatives.

Conformational impact of pentafluorosulfanylation on acyclic aliphatic molecules

The diastereotopic nature of geminal protons γ to the pentafluorosulfanyl (SF5) group was investigated by computational modeling and experimental methods. 1D and 2D NMR techniques were employed to determine the vicinal coupling constants used in the estimation of HCCH dihedral angles required for the approximation of the average solution conformation of SF5-substituted alkyl chains. Rotational energy barriers were calculated at the B3LYP/6-31++G (d,p) level in an effort to assess the relative steric demand of the SF5 group relative to a trifluoromethyl or tert-butyl group. The observed diastereotopicity is likely a result of hindered molecular rotation where one of the γ protons is trapped between two equatorial fluorines of the SF5 group.

Discovery of practical production processes for arylsulfur pentafluorides and their higher homologues, bis- and tris(sulfur pentafluorides): Beginning of a new era of “super-trifluoromethyl” arene chemistry and its industry

Various arylsulfur pentafluorides, ArSF5, have long been desired in both academic and industrial areas, and ArSF5 compounds have attracted considerable interest in many areas such as medicines, agrochemicals, and other new materials, since the highly stable SF5 group is considered a “super-trifluoromethyl group” due to its significantly higher electronegativity and lipophilicity. This article describes the first practical method for the production of various arylsulfur pentafluorides and their higher homologues, bis- and tris(sulfur pentafluorides), from the corresponding diaryl disulfides or aryl thiols. The method consists of two steps: (Step 1) treatment of a diaryl disulfide or an aryl thiol with chlorine in the presence of an alkali metal fluoride, and (step 2) treatment of the resulting arylsulfur chlorotetrafluoride with a fluoride source, such as ZnF2, HF, and Sb(III/V) fluorides. The intermediate arylsulfur chlorotetrafluorides were isolated by distillation or recrystallization and characterized. The aspects of these new reactions are revealed and reaction mechanisms are discussed. As the method offers considerable improvement over previous methods in cost, yield, practicality, applicability, and large-scale production, the new processes described here can be employed as the first practical methods for the economical production of various arylsulfur pentafluorides and their higher homologues, which could then open up a new era of “super-trifluoromethyl” arene chemistry and its applications in many areas.

Allosteric agonists of the calcium receptor (CaR): fluorine and SF5 analogues of cinacalcet

Three selectively fluorinated cinacalcet analogues are prepared and their activity as calcium-sensing receptor (CaR) agonists is assessed. Individual (2R,1'R)-2 and (2S,1'R)-3 fluorocinacalcet diastereoisomers were prepared using the MacMillan asymmetric fluorination reaction. Assays with the recombinant human CaR revealed that both diastereoisomers have a similar potency to each other although slightly lower (75-80%) than that of cinacalcet 1. The SF(5)-cinacalcet analogue 4 was prepared from meta-pentafluorosulfanyl benzyl alcohol and has ~75% agonist activity relative to cinacalcet 1 indicating that the SF(5) group can replace the CF(3) group and retain significant bioactivity.

Environmental properties of pentafluorosulfanyl compounds: Physical properties and photodegradation

The pentafluorosulfanyl (SF5) functional group was investigated from an environmental perspective to ascertain its physical properties and photolytic fate. Five aromatic probe compounds were compared with their trifluoromethyl analogs. Water solubilities for SF5 compounds ranged from 78 mg/L to 2.4 g/L. Octanol-water partitioning coefficients ranged from log K(OW) = 2.9 to 3.6, all of which were approximately 0.5 to 0.6 log units more hydrophobic than their trifluoromethyl analogs. The direct photolytic fate of SF5 compounds was studied, and the SF5 group was found to completely degrade using actinic radiation with hourly half-lives. The reaction was followed by high-performance liquid chromatography with a UV-visible detector, 19F nuclear magnetic resonance spectroscopy, and high-resolution mass spectrometry. It was found that five equivalents of fluoride were released to form a benzenesulfonate as a final product of photodegradation. Finally, an SF5 analog of fluometuron, a potentially new herbicide, was synthesized and likewise photolyzed. The present study provides the first evidence that pentafluorosulfanyl can degrade under mild, environmentally relevant conditions.

Radical Terpolymerization of 1,1,2-Trifluoro-2-pentafluorosulfanylethylene and Pentafluorosulfanylethylene in the Presence of Vinylidene Fluoride and Hexafluoropropylene by Iodine Transfer Polymerization

Iodine transfer terpolymerization of two monomers bearing an SF5 group, i.e., 1,1,2-trifluoro-2-pentafluorosulfanylethylene (F2CCFSF5) and pentafluorosulfanylethylene (H2CCHSF5), with 1,1-difluoroethylene (or vinylidene fluoride, VDF) and hexafluoropropylene (HFP) is presented. These pentafluorosulfanyl monomers present a peculiar reactivity. They do not homopolymerize by conventional radical polymerization, but they co- and terpolymerize with the above fluorinated olefins. The resulting fluorinated terpolymers were characterized by 19F and 1H NMR spectroscopies which enabled the assessment of the molar percentages of the three comonomers. Size exclusion chromatography and NMR characterizations were also used to assess the molecular weights, Mn, ranging between 260 and 8400 g/mol. Interestingly, both these pentafluorosulfanyl monomers exhibit different behaviors in that radical terpolymerization in the presence of C6F13I as a degenerative chain transfer agent. Thus, CF2CFSF5 can be terpolymerized with VDF and HFP with a good control of molecular weight leading fluoropolymers bearing SF5 groups with low polydispersity index (PDI). Unexpectedly, only two iodide functionalities of the terpolymers namely two end groups (−CH2CF2I and −CF2CH2I) were observed and their proportions were influenced by the number of VDF units. Indeed, −CH2CF2I functionality decreased when the number of VDFs per chain increased. In contrast to 1,1,2-trifluoro-2-pentafluorosulfanyl ethylene, H2CCHSF5 could not be terpolymerized by ITP but led to C6F13[(CH2CF2)(CH2CH(SF5)]nI alternating cooligomers of low molecular weight in poor yields (5−20%). The formation of byproduct (C6F13CHCHSF5 monoadduct obtained by dehydrofluorination) was also observed, which corresponds to the elimination of HI from the 1:1 adduct. In the last part, the thermal properties are discussed. The presence of SF5 group decreases the Tg of fluoropolymers whereas the thermal stabilities depended on the molecular weights.

Synthesis of Pentafluorosulfanylpyrazole and Pentafluorosulfanyl-1,2,3-triazole and Their Derivatives as Energetic Materials by Click Chemistry

1-Pentafluorosulfanyl acetylene and its derivatives react with azide or diazomethane giving rise to an SF5-substituted 1,2,3-triazole or pyrazole. The SF5 group increases density remarkably and as a result enhances the detonation performance of the energetic materials relative to the CF3 group.

Synthesis of Novel Pentafluorosulfanylfurans. Two Retro-Diels−Alder Approaches

The first examples of furan substituted with an SF5 group are reported. 3-pentafluorosulfanylfurans were prepared from their respective 2-pentafluorosulfanyl-5-cyano-7-oxabicyclo[2.2.1]hept-2-ene precursors via retro-Diels-Alder reactions. Also, a tandem cycloaddition/retrocycloaddition reaction between 4-phenyloxazole and 1-pentafluorosulfanylhex-1-yne was used to prepare 3-pentafluorosulfanyl-4-butylfuran. [reaction: see text].

Original SF5-Containing Fluorinated Copolymers Based on Vinylidene Fluoride

The radical co- and terpolymerization of fluorinated monomers bearing an SF5 group, XYCCZSF5 (where X, Y, and Z represent either H or F atoms) with 1,1-difluoroethylene (vinylidene fluoride, VDF or VF2) and hexafluoropropene (HFP), is presented. Although these SF5 monomers do not homopolymerize under radical initiation, they do copolymerize (and terpolymerize) in solution, in the presence of radical initiators with VDF (and with VDF and hexafluoropropylene (HFP)), hence leading to original copolymers bearing SF5 side groups. NMR characterizations and yields enabled one to compare the relative reactivities of F2CCFSF5, HFP, perfluoromethyl vinyl ether, and perfluoropropyl vinyl ether in the copolymerization of VDF with these fluoroolefins. The degree of fluorine substitution on the ethylenic unit of the SF5 monomers had an influence on their reactivity, on their relative incorporation in the copolymers, and on the molar masses of the resulting terpolymersthe higher the fluorine in the SF5 monomer, the higher molecular weight. Interestingly, the greater the degree of fluorine substitution of the SF5-containing monomer, the greater the yield of the reaction. The yield also increased as the amount of initiator was increased. The relative concentrations of the comonomers in each copolymer were assessed by 19F and 1H NMR spectroscopy. The thermal properties (thermal stability and glass transition temperature) of these resulting SF5-containing fluoropolymers were also examined.

Liquid Crystals Based on Hypervalent Sulfur Fluorides: Exploring the Steric Effects of ortho‐Fluorine Substituents

AbstractLiquid crystals that have ortho‐fluorinated pentafluoro‐λ6‐sulfanyl terminal groups are the most polar materials that are still compatible with current active matrix LCD technology. The synthesis of the first examples of this class of substance has been achieved by direct fluorination. The physico‐chemical characterization, supported by DFT calculations, revealed some surprising features of these new compounds: the bulky SF5 group is easily deformed and responds in a quite unusual way to the steric strain exerted by its ortho substituents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

SF5-Terminated Fluorinated Schiff Base Liquid Crystals

Novel liquid crystals based on fluorinated carbon chains and terminated with SF5 groups are presented for the first time. Attachment of an SF5 group separated from a benzylidine group by a fluorinated spacer leads to monotropic nematic and smectic phases, while an enantiotropic nematic phase is observed in mixtures. The phase sequence of these new compounds is comparable to hydrocarbon analogues of nO.m (n-alkoxy-m-alkylbenzylidine) series. Despite a long alkoxy chain, the nematic → smectic A transition is closer to second order, with ≈ 0.995 values that are even higher than for the nCB (n-alkylcyanobiphenyls) series. Single crystal and quantum computational studies suggest that electrostatic interactions play a major role in governing the value of MTCP. Molecular packing in the crystal structure exhibits monoclinic P21/a symmetry. A flexible synthetic strategy that allows the synthesis of another homologous series with a bend in the molecular structure is also presented. The bent core structure of 10O.2 SF5 investigated shows a monotropic, tilted smectic phase for the higher C10 alkoxy chain. The compounds in this series reveal a high degree of undercooling (well above 50 °C), which is rationalized using finite size effects on nucleation.

Perfluorinated polymer surfaces comprising SF 5-terminated long-chain perfluoroacrylate

A new perfluorinated acrylate monomer containing the SF 5(CF 2) 6-perfluorinated side chain was synthesized and polymerized into films. Bulk monomer characterization is consistent with the molecular structure based on FTIR, mass spectrometry and NMR analyses. The surface properties of polymer coatings were studied with aqueous wetting (contact angle) and X-ray photoelectron spectroscopy (XPS) methods. The surface composition is shown to be highly enriched in the terminal side chain SF 5-chemistry and exhibits properties consistent with a highly apolar, non-wetting perfluorinated polymer surface. Depth-dependent XPS studies using angular-resolved methods (ADXPS) confirmed a non-stoichiometric enrichment of sulfur and fluorine at the film ambient interface, consistent with a surface presence of the terminal SF 5-group and possibly film structural anisotropy in the surface zone. Time-of-flight (TOF) secondary ion mass spectrometry (SIMS) analysis supplements the XPS data by showing the presence of all expected SF 5-acrylate chemistry components in the outer 15 Å of the film surface.

The addition of SF 5Br to acrylic esters: pathways to γ-SF 5-propane derivatives

Reaction of SF 5Br with various acrylic esters, CH 2CHCOOR, where R = C 2H 5/C(CH 3) 3 and CH 2C(CH 3)COOCH 3, CH 2C(CH 2Cl)-COOC 2H 5, CH 2C( n-C 7H 15)COOC 2H 5 resulted in 1:1 adducts with the SF 5-group attached to the CH 2 portion of the acrylic ester. These adducts were converted to halogen-free saturated esters, an alcohol [SF 5(CH 2) 3OH] an acid [SF 5(CH 2) 2COOH] and a bromide [SF 5(CH 2) 3Br]. Therefore, a method for chain-elongation of SF 5-aliphatic hydrocarbons has been devised. With ethyl acrylate, a 2:1 adduct was also isolated. The reaction of SF 5Cl with (C 2H 5O) 2CCHCOOC 2H 5 gave chloromalonate. The compounds were characterized by their infrared, nuclear magnetic and mass spectral data.