Diphenyliodonium Salt Research Articles

Synthesis of a fluorinated photoresist for optical waveguide devices

A linear fluorinated bis-phenol-A novolac resin (LFAR) for optical waveguide was synthesized based on 4,4′-(hexafluoro-isopropylidene)diphenol, epoxy chloropropane and formaldehyde. Negative fluorinated photoresist (FP) was made by composing the LFAR, diphenyl iodonium salt and solvent. The film, which was made by spin-coating FP, had good UV light lithograph sensitivity, large hardness and high glass transition temperature (T g >170°C, after crosslinking). Low-loss optical waveguides with very smooth top surface were fabricated from the resulting FP by direct UV exposure and chemical development. For waveguides without upper cladding, the propagation loss of the channel waveguides was measured to be 0.21 dB/cm at 1550 nm.

A photo‐oxidizable kinetic pathway of three‐component photoinitiator systems containing porphrin dye (Zn‐tpp), an electron donor and diphenyl iodonium salt

AbstractA series of kinetic experiments were conducted involving visible‐light activated free radical polymerizations with three‐component photoinitiators and 2‐hydroxyethyl methacrylate (HEMA). Three‐component photoinitiator systems generally include a light‐absorbing photosensitizer (PS), an electron donor and an electron acceptor. To compare kinetic efficiency, we used thermodynamic feasibility and measured kinetic data. For this study, 5,10,15,20‐tetraphenyl‐21H,23H‐porphyrin zinc (Zn‐tpp) and camphorquinone (CQ) were used as the PSs. The Rehm‐Weller equation was used to verify the thermodynamic feasibility for the photo‐induced electron transfer reaction. Using the thermodynamic feasibility, we suggest two different kinetic mechanisms, which are (i) photo‐reducible series mechanism of CQ and (ii) photo‐oxidizable series mechanism of Zn‐tpp. Kinetic data were measured by near‐IR spectroscopy and photo‐differential scanning calorimetry based on an equivalent concentration of excited state PS. We report that the photo‐oxidizable series mechanism using Zn‐tpp produced dramatically enhanced conversions and rates of polymerizations compared with those associated with the photo‐reducible series mechanism using CQ. It was concluded from the kinetic results that the photo‐oxidizable series mechanism efficiently retards back electron transfer and the recombination reaction step. In addition, the photo‐oxidizable series mechanism provides an efficient secondary reaction step that involves consumption of the dye‐based radical and regeneration of the original PS. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3131–3141, 2009

Analysis of association constant for ground state dye-electron acceptor complex of photoinitiator systems and the association constant effect on the kinetics of visible-light-induced polymerizations.

We investigated the formation of ground state donor/acceptor complexes between xanthene dyes (rose Bengal (RB) and fluorescein (FL)) and a diphenyl iodonium salt (DPI) which is dissolved in 2-hydroxyethyl methacrylate (HEMA) monomer. To characterize the association constant of the complex, we have suggested a new analysis model based upon the Benesi-Hildebrand model. Because the assumption of the original Benesi-Hildebrand model is that the absorption bands are due only to the presence of the complex and that the absorption by the free component is negligible; the model cannot be applied to our systems, which is a dye-based initiator system. For each dye, the molar absorptivity of the ground state complex was evaluated as a function of wavelength and this analysis confirmed the validity of the modified Benesi-Hildebrand model. In addition, we observed the RB/DPI photoinitiator system failed to produce a perceptible polymerization rate but the FL/DPI photoinitiator system provided very high rates of polymerization. Based upon the association constant for these complexes, we concluded that the observed kinetic differences arise from the different association constant values of the ground state dye-acceptor complex, resulting in back electron transfer reaction.

Polythiophene derivatives by step-growth polymerization via photoinduced electron transfer reactions

A novel method for the step-growth polymerization of diphenyldithienothiophene in the presence of diphenyliodonium salt by photoinduced electron transfer is described.

Free‐radical‐promoted cationic photopolymerization under visible light in aerated media: New and highly efficient silane‐containing initiating systems

AbstractNew systems for the visible‐light‐induced polymerization of cationic resins working through a free‐radical‐promoted process are presented. They are based on a photoinitiator (camphorquinone, isopropylthioxanthone, Eosin), a silane, and a diphenyl iodonium salt, the new compound being the silane. The overall efficiency is strongly affected by the silane structure. The rates of polymerization and final percent conversion are noticeably higher than those obtained in the presence of already studied reference systems. Moreover, contrary to previously investigated free‐radical‐promoted cationic polymerizations, oxygen does not inhibit the process and an unusual enhancement of the polymerization kinetics is found in aerated conditions: such an observation seems to have never been reported so far. The excited state processes and the role of oxygen as revealed by laser flash photolysis are discussed. The particular behavior of the silyl radicals is outlined. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2008–2014, 2008

Photo‐Induced Cross‐Linking of Divinyl Ethers by Using Diphenyliodonium Salts With Highly Nucleophilic Counter Anions in the Presence of Zinc Halides

AbstractThis study describes the use of diphenyliodonium salts with highly nucleophilic counter anions to photoinitiate the cationic cross‐linking of divinyl ethers. Both direct and indirect initiating modes are used. In the direct acting system, only a diphenyliodonium salt with a highly nucleophilic counter anion and a zinc halide are employed as initiator and activator, respectively. In the indirect systems, in addition to direct system components, photosensitive additives such as anthrecene, perylene, 2,2‐dimethoxy‐2‐phenyl acetophenone, benzophenone, and thioxanthone, which absorb the energy of the incident light and activate the iodonium salt, are used to initiate polymerization. All systems employed in this study initiated quite vigorous polymerizations.magnified image

Photoreactive inclusion complex of aryliodonium salt encapsulated by methylated-β-cyclodextrin

A novel photoreactive inclusion complex (PIC) with an excellent water solubility was obtained by the complexation of methylated-β-cyclodextrin (Me-β-CD) with the hydrophobic 4,4′-dimethyl diphenyliodonium salt (DMDPI). The photoreactivity of the complex PIC was examined by the kinetic studies in order to evaluate the influence of Me-β-CD complexation. The photoreactive rate was enhanced in the photolysis of PIC compared with the uncomplexed DMDPI. By employing the photosensitizer at the visible region composed with PIC, the complex system can be used to initiate the photoreaction even in the visible region.

A practical route for synthesizing a PET ligand containing [ 18F]fluorobenzene using reaction of diphenyliodonium salt with [ 18F]F −

The aim of this study was to develop a practical route for preparing a fluorine-18 ([ 18F]) labelled ligand ([ 18F] 1) containing [ 18F]fluorobenzene ring by employing the reaction of diphenyliodonium salt with [ 18F]F −. Diphenyliodonium tosylate ( 2) was synthesized from tributylphenylstannyl compound ( 6) with [hydroxy(tosyloxy)iodo]benzene ( 7). Using this method, [ 18F]DAA1106 ([ 18F] 3a), a positron emission tomography ligand for imaging peripheral-type benzodiazepine receptor, was prepared.

Thermal and photopolymerization of divinyl ethers using an iodonium initiator: the effect of temperature

AbstractDifferential scanning calorimetry was employed to monitor the thermal polymerization and the photopolymerization kinetics of divinyl ethers by temperature‐ramping and isothermal modes, respectively, with a diphenyl iodonium salt photoinitiator and a thioxanthenone photosensitizer. For thermal polymerization of triethylene glycol divinyl ether (TEGDVE), the peak temperature (i.e. the temperature at the maximum rate) decreased with increased photoinitiator concentration and reduced scanning rate, but the final conversions were all very high (>90%). The exotherm was extremely narrow, suggesting that the reaction was inhibited by a cation scavenger until it was all consumed. The activation energy, determined by the Ozawa method, was 108 ± 7 kJ mol−1. With isothermal photopolymerization of the flexible divinyl ether TEGDVE, the final conversion rose from 30 to 70% with an increase in temperature from 40 to 80 °C. A similar trend but with much lower conversions was observed for a more rigid divinyl ether (bis[4‐(vinyloxy)butyl] terephthalate, BVEBT). For TEGDVE, the activation energy determined from the maximum photocuring rate was 43 ± 4 kJ mol−1, but the activation energy measured at a fixed conversion increased as the conversion rose. A similar value for the activation energy was found for the photocuring of BVEBT. The changes in the dynamic rheology were measured for TEGDVE during its photocuring and the gel point identified. Dynamic mechanical thermal analysis of the cured TEGDVE polymer showed it was a highly crosslinked network with Tg of 23 °C. The vinyl ethers could also be thermally cured by free radicals, but the extent of conversion was less than 33%. Copyright © 2007 Society of Chemical Industry

Enhanced degradation of cellulose acetate film containing diphenyliodonium salt–benzophenone

Cellulose acetate (degree of substitution 2.45) films containing diphenyliodonium salt and benzophenone were prepared and their degradative behavior was examined under simulated solar exposure. Acetic acid generation from the films under irradiation was greater in the co-presence of diphenyliodonium salt and benzophenone than in the sole presence of diphenyliodonium salt. Photosensitization and free-radical oxidization, which are followed by Bronsted acid generation, were postulated as the mechanism for the observed increase of deacetylation. The patterns of decreased molecular weight were different between the films with the diphenyliodonium salt and those with benzophenone; while the films with the diphenyliodonium salt kept a relatively constant molecular-weight distribution, the polydispersity increased in the films with benzophenone during the degradation. Since the synthesized characteristics of those two different patterns of change in molecular-weight distribution were observed in the co-presence of the diphenyliodonium salt and benzophenone, each additive appeared to act independently to lead to main-chain cleavage of cellulose acetate. Therefore, decrease in the molecular weight of cellulose acetate by diphenyliodonium salt did not seem to be enhanced in the co-presence with benzophenone.

Synthesis, Characterization and Lithography Performance of Photoacid Generator with Short Perfluoroalkyl Anion

A new environmentally friendly photoacid generator (PAG) consisting of diphenyliodonium salt as photoactive cation and fluoroalkyl sulfonium anion as counter ion was synthesized. From FT-IR measurement, it was found that non perfluorooctyl sulfonates (PFOS) PAG from UV irradiation could produce strong acid that subsequently catalyzes the deblocking of a protecting group in copolymer. A positive resist formulation at 248 nm based on the chemically amplified resist mechanism indicated that fluoroalkyl sulfonium anion was capable of providing good image profiles.

Diphenyliodonium Salts with Pyranine Conk as an Environment-friendly Photo-acid Generator and Their Applications to Chemically Amplified Resists

A diphenyliodonium salt with an environment-friendly dye as anion was designed. This salt was shown to possess photosensitivity suitable for use as a chemically amplified resist at both 365 and 405 nm. PAG of tris(diphenyliodonium) 9-hydroxy-pyrene-1,4,6-trisulfonate had a negative Ames test, showed good thermal stability, and had a decomposition temperature of 199.9 � C. The quantum yield of acid generation upon irradiation was 0.63. The mechanism of acid generation was intramoleculor electron transfer from the excited dye moiety to the iodonium structure. The photosensitivities of PAG in a polymer with a t-butoxycarbonyl protecting group were 31 and 58 mJ/cm 2

Visible-Light-Sensitive Photo-Acid Generator Incorporating Food Dye for Use in Chemically Amplified Resists

Diphenyliodonium 4-(3-N,N-diethylamino-6-diethyliminium-9-xantenyl)-3-sulfonato-phenylsulfonate was designed and prepared. The diphenyliodonium salt with a food dye as a counter anion showed good thermal stability, and had a decomposition temperature of 201.1°C. From the results of our investigation, the mechanism of acid generation is considered to be intramolecular electron transfer from the excited dye moiety to the iodonium. The photosensitivities of the photopolymer with a tetrahydropyranyl protecting group were 2.09 and 0.84 J/cm2 at 488 nm and 514 nm, respectively.

The role of diphenyl iodonium salt (DPI) in three‐component photoinitiator systems containing methylene blue (MB) and an electron donor

AbstractThree‐component initiators generally include a light‐absorbing photosensitizer, an electron donor that is often an amine, and the third component, which is usually an iodonium salt. To characterize the role of diphenyl iodonium chloride (DPI) in three‐component photoinitiator systems containing methylene blue (MB) as the photosensitizer, a systematic series of electron donors was used. The Rhem–Weller equation was used to verify the thermodynamic feasibility for photo‐induced electron transfer from the electron donors to the MB. Comparison of the photopolymerization rates of each two‐component initiator system (containing the photosensitizer and amine) to those of the corresponding three‐component system (with the addition of (DPI) allowed fundamental information regarding the role of the DPI to be obtained. It was concluded that the DPI enhances the photopolymerization kinetics in two ways: (1) it consumes an inactive MB neutral radical and produces an active phenyl radical, thereby regenerating the original methylene blue, and (2) it reduces the recombination reaction of the MB neutral radical and amine radical/cation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5863–5871, 2004

Development of a catalytic electron transfer system mediated by transition metal ate complexes: applicability and tunability of electron-releasing potential for organic transformations.

We have developed a catalytic electron transfer (ET) system composed of a transition metal ate complex (Me3M(II)Li; M = Co(II), Mn(II), Fe(II)) and magnesium. This system (catalytic Me3M(II)Li/Mg) turned out to be effective for various ET reactions, such as the desulfonylation of N-phenylsulfonyl amides, and others (the chemoselective cleavage of O-allyl groups, the reduction of nitro groups, the partial reduction of diketones, and the reductive coupling of diphenyliodonium salt). The ET ability of this system can be tuned by changing the ligands of the ate complexes. This tunability was experimentally and electrochemically demonstrated: alkoxy-ligated and dianion-type ET ate complexes showed attenuated and enhanced reducing abilities, respectively. The modification of the ET abilities was evaluated by means of electrochemical measurements and chemical reactions. These results provide a basis for the design of various tailor-made ET ate complexes.

Diphenyliodonium Salts with Diazoxide Group for A Photo-acid Generator

We designed diphenyliodonium salts with diazoxide group for a photo-acid generator (PAG) in chemically amplified resists. The absorption coefficients at 365 nm for the new PAGs were 103 -104 orders, originating in diazoxide structure. The quantum yield for acid generation irradiating 365 nm wavelength light of diphenyliodonium 1-diazo-2-hydroxynaphthalene-4-sulfonate (AZO-DPI) and diphenyliodonium 1-diazo-2-hydroxy-6-nitronaphthalene-4-sulfonate (NO2-AZO-DPI) was 0.21 and 0.14, respectively. The thermal stability of AZO-DPI and NO2-AZO-DPI were 144.2 and 153.2°C, respectively. The photosensitivity of AZO-DPI and NO2-AZO-DPI irradiating 365 nm wavelength light in polymer bearing ethoxyethyl protecting group were 120 and 98 mJ/cm2, respectively. The diphenyliodonium salt is the promising PAG sensitizing for 365 nm chemically amplified resists.

Promotion of Thermal Dehydration of Poly(vinyl alcohol) Film by Diphenyliodonium Salt

Abstract Thermal dehydration of a poly(vinyl alcohol) (PVA) film was greatly promoted by diphenyliodonium trifluoromethanesulfonate, which is known as a thermally stable photo acid generator. The oxidation of thermally generated PVA radicals by the salt is considered to lead to the dehydration. Liquid-nitrogen trapping of volatile products during the heating largely accelerated the dehydration for the salt-free film but not for the salt-containing film.

Effect of Poly(vinyl alcohol) on Radiation-induced Acid-generation of Diphenyliodonium Salt

Effect of Poly(vinyl alcohol) on Radiation-induced Acid-generation of Diphenyliodonium Salt

Radiation-induced chain reactions in alcohol solutions of diphenyliodonium salts: a high-sensitivity chemical dosimeter.

Chain reactions in gamma-irradiated 2-propanol solutions of diphenyliodonium salts have been studied. Protonic acids were generated in the irradiated solutions with high yields, whereas acid formation as a result of thermal reactions was negligible. The solution can be used as a high-sensitivity chemical dosimeter. The G value of acidic protons increases with increasing concentration of diphenyliodonium salt at the lower concentrations because the reaction rate of a propagation reaction increases. However, the chain is limited by a termination reaction between phenyl radical and the iodonium salt: The G value shows a maximum value of 610 micromol J(-1) at the concentration of 0.08 mol dm(-3) and decreases at higher salt concentrations.

Electrochemical arylation of cobalt and nickel chelates with diphenyliodonium salts

Electrochemical arylation of cobalt chelates with diphenyliodonium salts occurs at low cathodic potentials (viz., potential of the first reduction wave of the diphenyliodonium salt) and affords the phenyl derivatives of CoIII chelates containing the σ-Co—C(sp2) bond. Nickel complexes should be arylated at higher cathodic potentials because it is necessary to generate paramagnetic NiI complexes.