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Diaryliodonium salts (Ar2I+X−) are used as a photosensitive initiator that generates acid or radical species by ultraviolet light irradiation. Recently, sensitization of Ar2I+X− has gained importance owing to the escalating demand for high‐sensitive initiators with longer wavelength absorption such as 365 and 436 nm. However, the mechanism of photolysis of Ar2I+X− has not been strictly elucidated. This paper shows discussions of the details of its mechanism. Herein, we analyzed the photosensitization of Ar2I+X− with 2–isopropylthioxanthone (ITX) based on transient absorption techniques. As a result, it was revealed that electron transfer occurred from a triplet excited state of ITX to Ar2I+X− with an electron transfer rate constant of 4.2 × 109 s−1. Furthermore, high performance liquid chromatography measurements found the quantum yield of the photolysis was determined to be 0.48. [ABSTRACT FROM AUTHOR]

The investigation of thioxanthones involved molecular docking, molecular dynamics simulation, synthesis, and evaluation of their potential as anticancer agents. Molecular docking analyses indicated that 2,4‐dichloro‐1,3‐dihydroxythioxanthone and 2,4‐dibromo‐1,3‐dihydroxythioxanthone had lower binding energies and 4‐bromo‐1,3‐dihydroxythioxanthone had the similar binding energy compared to erlotinib. In 50 ns molecular dynamics simulation, 2,4‐dichloro‐1,3‐dihydroxythioxanthone and 2,4‐dibromo‐1,3‐dihydroxythioxanthone complex exhibited more stability than 4‐bromo‐1,3‐dihydroxythioxanthone and erlotinib, while it had similar stability with doxorubicin. These compounds comply the Lipinski's rule parameters and the minimum required parameters of ADMET. The evaluated anticancer activity of 2,4‐dichloro‐1,3‐dihydroxythioxanthone and 2,4‐dibromo‐1,3‐dihydroxythioxanthone revealed them inactive against cervical cancer (HeLa) and colorectal cancer (WiDr) with IC50 more than 100 μM, however was moderate activity toward breast cancer (T47D) and lung cancer (A549). The selectivity index (SI) values of those compounds (7.71–148.4) passed the parameter SI. Based on these findings, 2,4‐dibromo‐1,3‐dihydroxythioxanthone was the most promising anticancer candidate for T47D cancer cell. [ABSTRACT FROM AUTHOR]

In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol–gel chemistry, thus avoiding its release. Both liquid 1H and solid-state 29Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network. Notably, the laser flash photolysis, fluorescence, and electron paramagnetic resonance spin-trapping (EPR ST) experiments demonstrated that TXS could react with Iod through an electron transfer reaction through its excited states, leading to the formation of radical initiating species. Interestingly, the TXS/Iod was demonstrated to be an efficient photoinitiating system for free-radical (FRP) and cationic (CP) polymerization under LEDs@385, 405, and 455 nm. In particular, whatever the epoxy monomer mixtures used, remarkable final epoxy conversions were achieved up to 100% under air. In this latter case, we demonstrated that both the photoinduced sol–gel process (hydrolysis of trimethoxysilane groups) and the cationic photopolymerization occurred simultaneously. [ABSTRACT FROM AUTHOR]

In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol–gel chemistry, thus avoiding its release. Both liquid 1H and solid-state 29Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network. Notably, the laser flash photolysis, fluorescence, and electron paramagnetic resonance spin-trapping (EPR ST) experiments demonstrated that TXS could react with Iod through an electron transfer reaction through its excited states, leading to the formation of radical initiating species. Interestingly, the TXS/Iod was demonstrated to be an efficient photoinitiating system for free-radical (FRP) and cationic (CP) polymerization under LEDs@385, 405, and 455 nm. In particular, whatever the epoxy monomer mixtures used, remarkable final epoxy conversions were achieved up to 100% under air. In this latter case, we demonstrated that both the photoinduced sol–gel process (hydrolysis of trimethoxysilane groups) and the cationic photopolymerization occurred simultaneously.

Purpose: To evaluate the bond strength to dentin produced by experimental adhesives formulated with an elastomeric methacrylate monomer (EMM) and an alternative initiator system based on a Thioxanthone derivative (QTX). Materials and Methods: A self-etching primer was used. For the bonding resin, a model adhesive (G1) was formulated containing bis-GMA/TEG-DMA/HEMA (co-monomeric blend) + CQ/EDAB (initiator system). The other groups were formulated by adding to this formulation: EMM only (G2), QTX (G3), or EMM and QTX (G4). Clearfil SE Bond was used as the commercial control group. Fifty bovine teeth (n = 5) were restored with each one of the five adhesives. After restorative procedures, half of the specimens were stored in distilled water at 37°C for 24 h. The other half was fixed on a metal stub and subjected to 200,000 mechanical (50 N loading at 2 Hz frequency) and 1000 thermal cycles (5°C and 55°C). Afterwards, specimens were serially sectioned into beams and tested in tension until fracture. Bond strengths were statistically analyzed by two-way ANOVA and Tukey's test (a = 5%). Results: After 24 h, significantly higher µTBS was observed for the formulation containing EMM and QTX (G4) when compared to Clearfil SE Bond (p < 0.05). No significant differences in µTBS were detected among the experimental groups after 24 h (p>0.05). After thermomechanical cycling, no significant differences were observed among groups. Conclusion: The addition of EMM and QTX can be considered as possible alternative in dental adhesive formulations. [ABSTRACT FROM AUTHOR]

Thioxanthone derivatives were docked, synthesized, and tested for their anticancer activity. The molecular docking results showed that 1‐hydroxythioxanthone, 2‐chloro‐1‐hydroxythioxanthone, and 4‐chloro‐1‐hydroxythioxanthone gave lower binding energy than erlotinib demonstrating that those thioxanthones have stronger interaction in the active site of EGFR protein. The addition of one hydroxyl and chloro groups on 1‐hydroxythioxanthone greatly enhanced its inhibition in EGFR protein. All thioxanthone derivatives had hydrogen bonding interaction with MET769 residue. The in vitro anticancer assay against all cancer cells (T47D, HeLa, WiDr, A549) revealed that 2‐chloro‐1‐hydroxythioxanthone and 4‐chloro‐1‐hydroxythioxanthone gave lower IC50 than 1‐hydroxythioxanthone due to the addition of one chloro substituent. Meanwhile, 1,3‐dihydroxythioxanthone exhibited the strongest anticancer activity, as well as the highest selectivity index (3.22–19.55) among the other thioxanthones. Based on these findings, 1,3‐dihydroxythioxanthone is a potential anticancer drug candidate for further development in the future. [ABSTRACT FROM AUTHOR]

Plasmodium falciparum (P. falciparum) is the most fatal among the other Plasmodium parasites that infect humans with the malaria disease. Currently, the resistance of P. falciparum against some antifolate drugs has become a severe problem. On the other hand, xanthone and thioxanthone derivatives have been reported to have remarkable antimalarial activity. However, molecular docking studies have not evaluated thioxanthone derivative compounds as antimalarial agents. Accordingly, this research investigated the binding pose and inhibition mechanism of several thioxanthone derivatives against P. falciparum proteins DHFR (PDB ID: 1J3K) and DHODH (PDB ID: 1TV5) through molecular docking study. The compound structures were geometrically optimized using Gaussian 09 software and docked to the receptors using AutoDock4 software. The results showed that the free binding energy of thioxanthone derivatives ranged between -6.77 to -7.50 and -8.45 to -9.55 kcal mol–1 against pfDHFR and pfDHODH, respectively, with RMSD values of less than 2 Å. Compound F (4-iodo-3,4-dihydroxy-thioxanthone) gave the most substantial free binding energy against both proteins. Furthermore, the hydrogen bond interaction of compound F was the same as the native ligands of pfDHFR and pfDHODH. These results suggested that compound F has a more robust interaction in pfDHFR and pfDHODH. Thus, it is promising to further evaluate the compound as a candidate for a new antimalarial agent.

Thioxanthone (TX) and its derivatives have broad application prospects for their excellent absorption properties in the near UV range, high hydrogen scavenging capacity and ease of adjusting with LED light source. Herein, N‐(9‐oxo‐9H‐thioxanthen‐2‐yl)acrylamide (TXAM) was designed and synthesized as a LED‐sensitive photoinitiator. TXAM exhibited a maximum absorption band matched with the LED emission spectra (e. g., 385–405 nm). Its properties were investigated via density functional theory (DFT) calculations and experiments. The results suggested that TXAM could efficiently initiate free radical polymerization as a sole‐component photoinitiator upon LED irradiation; Meanwhile, a two‐component system with an iodonium salt could initiate cationic polymerization and free radical/cationic hydric photopolymerization. It also could be used for deep curing system to make the interpenetrated polymer network materials. [ABSTRACT FROM AUTHOR]

Thioxanthone derivatives are synthesized as one-component photoinitiators via a simple condensation reaction between thiosalicylic acids and heterocyclic aromatic hydrocarbons in a concentrated sulfuric acid medium. TX-C (Thioxanthrone–carbazole), TX-N-I (Thioxanthrone–N-methylindole) and TX-I (Thioxanthrone–indole) are characterized by 1HNMR (nuclear magnetic resonance), FTIR (fourier transform infrared spectroscopy), ultraviolet–visible spectrophotometry, fluorescence spectroscopy, elemental analysis and TG (thermal gravimetric analysis). TX-N-I and TX-I both possess an absorption characteristic similar to the parent thioxanthone with a maximum at 397nm (ε = 3240 L mol−1 cm−1) and 395 nm (ε = 1920 L mol−1 cm−1). The introduction of heterocyclic structures makes the maximum absorption peak red-shifted by 10 nm compared to TX. Its capabilities to act as initiator for the photopolymerization of PEGDA (polyethylene glycol diacrylate) and TMPTA (trimethylolpropane triacrylate) in the absence and presence of TEOA (triethanolamine) media are also examined. TX-N-I acts as an efficient initiator in the UV curable ink, whose light curing time is only 12 s. [ABSTRACT FROM AUTHOR]

The photodriven radical-mediated [3 + 2] cyclization reaction was found to yield polymers efficiently without being hindered by degradative chain transfer. The first reaction is a hydrogen abstraction process in which one hydrogen atom migrates from the α-methylene group of an allyl monomer to the triplet state (or fragments) of the photoinitiator, thus yielding primary allyl radicals as primary radicals and then begins chain propagation via a 3 + 2 cyclization reaction. Allyl ether monomers were found to be significantly higher than other allyl monomers even with the absence of amine-like synergists. In order to clarify the procedure of the hydrogen abstraction mechanism, we used four allyl-type monomers as hydrogen donors and three thioxanthone photoinitiators as hydrogen acceptors by the quantum chemistry method in terms of geometry and energy. The results were interpreted with transition-state theory and the interaction/deformation model. Then, the tunneling factors of hydrogen abstraction reactions were also investigated by Eckart’s correction. The results show allyl ether systems are more reactive than other allyl systems, and it would provide us with new insights into these hydrogen abstractions.

A novel photoinitiator (PI) is described here for low ecological impact, p(PEGDA575‐TX): It is water soluble, polymerizable, thioxanthone (TX) functional, and is a one‐component poly(ethylene glycol)‐based poly(β‐amino ester). The PI is synthesized in one step via classical aza‐Michael addition reaction between poly(ethylene glycol) diacrylate (Mn = 575 D) and amine functionalized TX (2‐(2‐aminoethoxy)‐9H‐thioxanthen‐9‐one). It absorbs at ≈ 404 nm (ε = 14 000–44 309) in water and can photodecompose with or without additives such as ethyl 4‐(dimethylamino)benzoate (EDB) and bis‐(4‐tert‐butylphenyl)‐iodonium hexafluorophosphate (Iod). Although it is an effective one‐component visible light PI for free radical polymerization of di‐ and tri(meth)acrylates, EDB or Iod will be favorable for synergistic effect. p(PEGDA575‐TX) has higher initiating reactivity, reducing ability of oxygen inhibition and migration stability compared to TX, which make it environmental friendly. [ABSTRACT FROM AUTHOR]

[Display omitted] The scope of applications of photopolymerization is in constant evolution and the migration of photoinitiators within the polymer networks is now the focus of numerous safety concerns, especially for different applications such as food production and packaging, dentistry, biomaterials and regenerative medicine. Among popular photoinitiators, thioxanthone is one of those. However, thioxanthone is a small molecule that can easily migrate within the polymer network. Face to the migratability issues that have notably been evidenced in 2005 with a famous thioxanthone derivative, namely 2-isopropylthioxanthone (ITX) that could be found in baby milk and different milk products, researchers have thus been incited to develop photoinitiators that can be connected to the polymer chains using these thioxanthones as initiating species for the polymerization of acrylates or methacrylates but also as co-polymerizable structures by introducing groups such as acrylates or methacrylates on the thioxanthone scaffold. In this review, the different strategies examined to immobilize thioxanthone by copolymerization or by radical addition on monomers are detailed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Designed and synthesised recyclable ionic liquid photocatalysts IL-TX. • IL-TX has good photocatalytic properties. • IL-TX catalysed α-cyanation reaction of aromatic tertiary amines. • The catalytic activity only slightly decreased after being reused 6 times. A stabile and recyclable photocatalyst IL-TX was designed and synthesized by introducing the dye photocatalyst thioxanthenone into ionic liquids and its excellent photocatalytic performance was demonstrated by photophysical and electronic performance tests. The IL-TX was applied as a recyclable photocatalyst for α-cyanidation reaction of aromatic tertiary amines in MeOH at room temperature under blue light irradiation, and a range of cyanide products were obtained in good to excellent yields. Furthermore, the practicality of this protocol was further demonstrated through the optimization of the synthesis of the drug praziquantel and the natural product 8-oxopseudopalmatine. This study provides a greener and sustainable solution for photocatalytic cyanation reaction. [ABSTRACT FROM AUTHOR]

Visible light catalysis provides an important platform for developing green and sustainable catalytic processes. However, traditional photosensitizers have limited their application due to their inherent limitations. Due to the structural stability and recyclability of ionic liquids (ILs), a bifunctional catalyst TXIL-Ni was designed and synthesized by introducing the photosensitizer thioxanthone (TX) and transition metal Ni(II) into ILs. TXIL-Ni exhibited remarkable photocatalytic activity for C7–H acylation of indolines to efficiently synthesize pyrroloquinolinone derivatives by a tandem cyclization reaction of decarboxylation acylation and Claisen-Schmidt condensation. The protocol provided a new strategy for the synthesis of the natural product Viridicatol and the key intermediate of farnesyltransferase inhibitors. The experimental results indicated that thioxanthone-based ionic liquid TXIL-Ni as a synergistic photocatalyst has the advantages of mild reaction conditions, recyclability, and atomic economy. This provides a new solution for the design of multifunctional and reusable catalysts. [Display omitted] • A novel thioxanthone-based ionic liquid bifunctional catalyst TXIL-Ni was designed. • TXIL-Ni exhibited excellent catalytic activity in the synthesis of pyrroloquinones. • Pyrroloquinones were efficiently synthesized by a green and mild tandem reaction. • TXIL-Ni as photocatalyst could be recycled at least six runs. [ABSTRACT FROM AUTHOR]

Herein, N‐benzyl‐N‐(9‐oxo‐9H‐thioxanthen‐2‐yl)acrylamide (TXNBA) is designed and synthesized as one‐component polymerizable photoinitiator (PI). It is investigated in terms of its photophysical/photochemical, kinetic, and migration stability properties by ultraviolet‐visible spectrophotometer, Fourier transform infrared spectrometer, and EPR spin trapping experiments. In conjunction with the experimental studies, series of density functional theory calculations are performed and various photophysical and photochemical properties are computationally calculated and visualized. The photolysis and photoinitiation mechanism of TXNBA is clarified. Comparison of the results of 2‐isopropylthioxanthone (ITX) system has shown that TXNBA is an efficient one‐component polymerizable PI with excellent migration stability. The photoinitiator's migration ratio of TXNBA system to ITX system is 8.52%. [ABSTRACT FROM AUTHOR]

2-thioxanthone thioacetic acid (TXSCH2COOH, T), which has a fluorometric character, was used for new fluorometric system upon Fe(II) analysis in biological samples as the main target. T-BSA binary complex was firstly consisted with non-covalent interactions between T and BSA at the equilibrium concentration as 1.77 × 10-4.M. T-BSA binary complex emission was increased at the ratio of 24.40% due to stabilization property of BSA (pH:7), compared with T emission intensity. Fluorescence emission spectroscopy was used for the all measurements because of an economic, a sensitive and a practical method compared with other spectroscopic analysis. T-BSA-Fe(II) triple complex was also obtained by adding Fe(II) ion to T-BSA binary complex solution. Its characterization was performed to be investigated with optimum excitation wavelength, buffer concentration, pH and temperature as 297 nm, 10-3 M Tris HCl (10-2M NaCI), pH:7.2 at 25 °C, respectively. The results of Fe(II) analysis in serum showed a certain response in fluorometric T-BSA-Fe(II) triple complex measurement system as 50.42 ± 5.8 µg/dL. The analyses of our fluorometric triple complex system were compared with the reference electrochemiluminescence method and similar results were obtained. Fluorometric measurements of T-BSA-Fe(II) triple complex, its characterization and Fe(II) analysis in this system have not been investigated in literature gives originality to our study. [ABSTRACT FROM AUTHOR]

Oligonucleotides with the sequences 5′-GTG AUPA TGC, 5′-GCA TAUP CAC and 5′-GUPG ATA UPGC, where UP is 2′-O-propargyl uridine, were subjected to post-synthetic Cu(I)-catalyzed azide–alkyne cycloaddition to attach 1,4,7,10-tetraazacyclododecane (cyclen) and two well-known DNA intercalating dyes: thioxanthone and 1,8-naphthalimide. We propose a convenient cyclen protection–deprotection strategy that allows efficient separation of the resulting polyamine–oligonucleotide conjugates from the starting materials by RP-HPLC to obtain high-purity products. In this paper, we present hitherto unknown macrocyclic polyamine–oligonucleotide conjugates and their hybridization properties reflected in the thermal stability of thirty-two DNA duplexes containing combinations of labeled strands, their unmodified complementary strands, and strands with single base pair mismatches. Circular dichroism measurements showed that the B-conformation is retained for all dsDNAs consisting of unmodified and modified oligonucleotides. An additive and destabilizing effect of cyclen moieties attached to dsDNAs was observed. Tm measurements indicate that placing the hydrophobic dye opposite to the cyclen moiety can reduce its destabilizing effect and increase the thermal stability of the duplex. Interestingly, the cyclen-modified U showed significant selectivity for TT mismatch, which resulted in stabilization of the duplex. We conclude the paper with a brief review and discussion in which we compare our results with several examples of oligonucleotides labeled with polyamines at internal strand positions known in the literature.

An efficient synthetic method of aromatic ketones through C−F cleavage of trifluoromethyl group is disclosed. The high functional group tolerance of the transformation and the remarkable stability of trifluoromethyl group in various reactions enabled multi‐substituted aromatic ketone synthesis in an efficient route involving useful transformations such as ortho‐lithiation, aryne chemistry, and cross‐couplings. [ABSTRACT FROM AUTHOR]

Three polymethylhydrosiloxane (PMHS)‐modified thioxanthone (TX) visible macrophotoinitiators (TX‐PMHSs) were designed and prepared by the partially hydrosilylation of 2‐allyl(methyl)amino‐9H‐thioxanthen‐9‐one (TX−A) and PMHS. Their characteristics of photopolymerization, photolysis, reduction of oxygen inhibition and the modification of the polymer materials were discussed. As sole‐component visible photoinitiators, TX‐PMHSs could even initiate 1, 6‐hexanedioldiacrylate (HDDA) polymerization in the air atmosphere. Moreover, TX‐PMHSs changed the surface wettability property of the cured polyurethane diacrylate prepolymer (PUA) film, and improved the thermal stability of the polymer network. Thus, this work provided an efficient strategy to decrease oxygen inhibition and improve the cured polymer material properties. [ABSTRACT FROM AUTHOR]

An efficient thioxanthone synthesis from benzoic acid esters is disclosed. Various thioxanthones were prepared by iridiumcatalyzed C-H borylation of benzoic acid esters followed by copper-catalyzed deborylthiolation and direct acid-mediated cyclization. We also achieved a synthesis of benzo-fused thioxanthones through a transformation of an aryne intermediate having an ester moiety. [ABSTRACT FROM AUTHOR]

Developing the single‐molecule white‐light emitters (SMWLEs) at room temperature is very challenging for pure organic metal‐free system, and it is even more challenging to achieve the high efficiency of pure organic SMWLE. Here, alkoxy substituents are tailored at 2‐positioned thioxanthone (TX) to finely tune the molecular packing mode and the intermolecular interaction between TX units, and the photoluminescence (PL) efficiency (ΦPL) of SMWLE is improved successfully from 1.5% (TX) to 45.0% (TX‐OCH(CH3)2). This simultaneous enhancement of dual emission between fluorescence and phosphorescence can be ascribed to i) a moderate intersystem crossing (ISC) rate for the equilibrium distribution between singlet and triplet excitons, ii) simultaneously accelerated radiative rates of singlet and triplet excitons due to J‐aggregation of TX units, and iii) effective suppression of nonradiation through strong hydrogen bond interactions by alkoxy chains. As a result, this work provides a novel molecular design strategy to harvest high‐efficiency pure organic SMWLE using a precise manipulation of π–π stacking mode and intermolecular interaction by tailoring alkoxy substituents. [ABSTRACT FROM AUTHOR]

The activation or functionalization of the saturated C-H is an extremely active field at present. We have explored the triplet state thioxanthone in reactivity of the hydrogen transfer reaction between donors and acceptors. In our works, two donors with quasi-inert sp3 C-H of skipped diene (3,6-nonadiene) and cyclic acetals (benzodioxole) reacted with type II photoinitiators (triplet state of thioxanthone series, TXs) as acceptors are investigated. The excited energies of TXs were obtained by time-dependent density functional theory (TD-DFT). TXs show obvious photosensibility based on their low reorganization energies (< 60 kcal mol−1). The isoentropy reactions had linear geometries of transition state (TS). The distortion/interaction model was used to probe the existence of interaction between acceptors and donors in saddle point. The distortion energy and activation barrier of benzodioxole are much higher than those of the corresponding 3,6-nonadiene. The lower bond dissociation energy noticeably affect the transition state. The reaction of triplet state of TXs with skipped dienes were found to have an anomalous low tunneling factors by using Wigner correction and early transition state by using the bond-energy–bond-order method. The triplet state of TXs photoinitiator can induced the hydrogen abstraction from saturated cyclic acetals and the skipped alkadienes. The hydrogen abstraction experiment are confirmed by UV and real-time FTIR. [ABSTRACT FROM AUTHOR]

A series of 3-substituted-4-chloro-thioxanthones and their corresponding S , S -dioxidethioxanthone derivatives were designed and synthesized. The effects of our synthesized compounds on cell viability toward the MCF-7 and MDA-MB-468 breast cancer cell lines were evaluated. The most active compound was 4f, which was active against the MCF-7 and MDA-MB-468 cell lines with respective IC 50 values of 7.2 and 3.9 μM. Interestingly, compound 4f did not impair cell viability of the cardiac myoblast H9C2 cell line (IC 50 > 25 μM), indicating that this compound might not exhibit cytotoxic effects on the normal cardiac cells. Further, compounds 4b , 4f , 4j , 4s , 5b , 5f , 5j, and 5s were characterized by the NCI screening system. Results revealed that compounds 4f and 4s had effective anticancer activities against various cancer cell lines. Finally, our results indicated that the 3-substituted-4-chloro-thioxanthone derivatives have the potential to be further developed as promising small molecules for anticancer applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Photopolymerization is an unavoidable polymerization technique used in plethora applications. If benzophenone or thioxanthone have been popular UV photoinitiators, these two structures are unsuitable for performing polymerization experiments in the visible region due to insufficient absorptions. With regards to thioxanthone and in order to redshift its absorption towards the visible range, numerous core-extended thioxanthones have been proposed, enabling to shift their absorptions at longer wavelengths and thus to elaborate visible light photoinitiators. In this field, thioxanthonation of dyes has been extensively studied but the major drawback of this approach was the access to polyaromatic structures exhibiting a low solubility in monomers, adversely affecting the monomer conversion. To address this issue, innovative strategies were envisioned to extend the π-conjugation of thioxanthone while providing an excellent solubility to photoinitiators both in common organic solvents and in monomers. In this review, the different strategies developed to access to these core-extended thioxanthones are detailed and the photopolymerization performance discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A polymerizable vinyl thioxanthone derivative (ETX) and two macromolecular photoinitiators (PPI1 and PPI2) based on ETX were synthesized. • ETX exhibited high initiation ability at 405nm LED lamps and PPI2 was a one component photoinitiator with high performance. • The molecular weight of macromolecular photoinitiators was lower than 4000. • The migration stability of these photoinitiators in the photocured fims were better than that of ITX. Photopolymerization technology has been limited in the application of the field of food packaging and biomedicine due to the high migration of the small molecule which are mostly from the photoinitiators. To improve migration stability of photoinitiators, polymerizable 2-vinyl thioxanthone (ETX) was synthesized by thiosalicylic acid and 4-fluorobenzaldehyde. Moreover, to further reduce the migration of photo- or co-photoinitiator, two macromolecular photoinitiators (PPI1, PPI2) were prepared by copolymerization of ETX with dimethylaminoethyl methacrylate (DMAEMA). The initiation activity of the prepared photoinitiators was studied by real-time FTIR spectroscopy. The results indicated ETX/triethanolamine (TEOA) system exhibited higher initiation performance than ITX/TEOA system by irradiation of 405 nm LED lamp, PPI2 as a one component photoinitiator displayed favorable initiation ability. In addition, the migration of ETX, PPI1 and PPI2 in the photocured film was declined obviously. ETX, PPI1 and PPI2 with low migration have potential application in the field of food package and biological materials. [ABSTRACT FROM AUTHOR]

Two novel kinds of photoinitiators were synthesized used as type II polymerizable photoinitiators with good migration stability in comparison with BP and ITX. The photoinitiator BRA exhibits only about 10% migrant value of BP and TXRA has 12%–25% migrant value of ITX. • Two novel kinds of low migration photoinitiators BRA and TXRA were synthesized. • The spectral properties were studied by Ultraviolet–Visible (UV–vis) spectroscopy. • The photo-initiating activity of the initiators was evaluated by real-time RT-IR. • The synthesized photoinitiators show almost similar initiating activity as the reference. • The synthesized photoinitiators exhibit about 10%–25% migrant value of the reference. Two novel kinds of low migration photoinitiators BRA and TXRA based on benzophenone (BP) and thioxanthone (ITX) were synthesized and used as Type II polymerizable photoinitiators. The structures were confirmed by proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR), FT-IR and high resolution MS. The spectral properties were studied by Ultraviolet–Visible (UV–vis) spectroscopy. The photo-initiating activity of the initiators was evaluated by real-time RT-IR in the presence of a hydrogen donor such as triethylamine. The results show that they exhibited almost similar initiating activity as the reference BP or ITX, while exhibiting more low migration than the non-functionalized BP or ITX. These results suggest that BRA or TXPA is an efficient photoinitiator for reducing migration in photo-curing system. [ABSTRACT FROM AUTHOR]

Thioxanthones (TXs) are not only important photoinitiators for free radical polymerization but also efficient light-harvesting units for organic light emitting diodes. Here, we reported synthesis and photophysical properties of new TXs with 2,2′-bipyridyl (BPy) and 2,2':6′,2″-terpyridyl (TPy) substituents, TXOBPy and TXOTPy, as well as those of their complexes with some transition metal ion (Zn2+, Fe2+, Ni2+, Eu3+ and Tb3+) solution in diverse solvents and solid powders. Absorption spectra revealed mainly two groups of bands at approximately 250–290 and 366 nm, attributed to the π–π* and n–π* electron transfer of the TXs. A broad luminescent emission was recorded and centered at approximately 422 nm for these TXs and their metal complexes, its relative intensity was solvent and concentration dependent. Further, it was observed that this emission band red shifted to approximately 470 nm in their solid powders. For the TXs and their Zn/Fe/Ni-complexes in the methanol solutions, the quantum efficiency (QE) of TX rings was about 0.04–0.11, and the fluorescent lifetime (τ) was about 0.5–1.2 ns. On the other hand, for the Fe and Ln-complexes, the QE of TX rings was below 0.01, which was attributed to the reason that the excited energy of the TX rings was quenched by ligand-Fe2+ charge transfer or by transferring the energy to the central Ln3+ (Eu3+ and Tb3+) ions. Thus, the Ln-TXOBPy and Ln-TXOTPy complexes gave off strong and sharp Eu3+/Tb3+ emissions at the wavelengths between 480 and 750 nm. The fluorescent emission lifetime of the central Ln3+ ions was about 0.3–0.6 ms. Thus, we can suggest that the TXOBPy and TXOTPy photoinitiators can act as potential candidates for the development of efficient emitters with tunable light emissions and luminescent sensors. Image 1 [ABSTRACT FROM AUTHOR]

Polymeric photoinitiators are widely used in ultraviolet (UV)-curable printing inks because of their low migration behavior. In this study, a new phenylphosphine oxide-polystyrene-thioxanthone (PPO-PSt-TX) polymeric photoinitiator was synthesized. Bis[(4-hydroxy)phenyl]phenyl phosphine oxide (BHPPO) that was synthesized by Grignard technique, was functionalized with 2-bromopropionyl bromide (atom transfer radical polymerization (ATRP) initiator) and then used in styrene polymerization. The bromine end-capped polystyrene was then reacted with 2-thioxanthone-thioacetic acid and final polymeric photoinitiator PPO-PSt-TX was obtained. Proton nuclear magnetic resonance (1H NMR), attenuated total reflectance- Fourier transform infrared spectroscopy (ATR-FTIR), gel permeation chromatography (GPC) and ultraviolet-visible spectroscopy (UV-Vis) confirmed the obtained structure. The curing characteristic of PPO-PSt-TX was compared with a standard flexographic printing varnish formulation containing thioxanthone (TX). The photopolymerization kinetics were determined by photo differential scanning calorimetry (Photo-DSC). The conversion of methylmethacrylate polymerization by using macrophotoinitiator is 78%. The migration behavior of PPO-PSt-TX was identified with liquid chromatography-mass spectrometry (LC-MS). It was shown that PPOPSt- TX macro photoinitiator is suitable for flexographic varnish and the migration level of photoinitiator is reduced by using polymeric photoinitiator. [ABSTRACT FROM AUTHOR]

Aiming to overcome the disadvantages of small molecule photosensitizers, a novel macromolecular photosensitizer was designed and synthesized in this work. Firstly, the functional small molecule photosensitizer 9-oxo-9H-thioxanthene-2-carboxylic acid (TX-COOH) and precursor poly(2-hydroxyethyl methacrylate) (PHEMA) was individually synthesized. Then, the macromolecular photosensitizer PHEMA-TX was realized by an optimized reaction procedure between PHEMA and TX-COCl, which was previously prepared by acyl chlorination of TX-COOH. The modification efficiency was calculated as 64%. Finally, the photocatalytic reaction using the as-synthesized PHEMA-TX was investigated based on three substrates of tris(4-methoxyphenyl)phosphane, methyl(phenyl)sulfane, (4-methoxyphenyl)boronic acid. The results showed that the photocatalyst PHEMA-TX can be easily separated, recovered by a simple precipitation, and reused 7 times without significant loss of the catalytic activity. The excellent photocatalytic property, easy separation, and recyclability of PHEMA-TX were comprehensively confirmed, which contributed great potential of this novel macromolecular photosensitizer in future application. Image 1059 • A novel synthetic method of thioxanthone-containing macromolecular photosensitizer was developed. • This PHEMA-TX showed nice photocatalytic activity in photo oxidation of triarylphosphane, sulfane and arylboronic acid. • This photocatalyst PHEMA-TX could be easily separated, recovered by a simple precipitation, and reused. [ABSTRACT FROM AUTHOR]

[Display omitted] • The structure–activity relationship was established for multiple series of conjugates. • The biological activity of the conjugates was compared and analyzed. • The influence of conjugate structure on their DNA interactions was investigated. • A practical method for the synthesis and purification of the conjugates was presented. The study investigated the structure–activity relationship of newly synthesized dye-linker-macrocycle (DLM) conjugates and the effect of each component on various biological properties, including cytotoxicity, cellular uptake, intracellular localization, interaction with DNA and photodynamic effects. The conjugates were synthesized by combining 1,8-naphthalimide and thioxanthone dyes with 1,4,7,10-tetraazacyclododecane (cyclen) and 1-aza-12-crown-4 (1A12C4) using alkyl linkers of different lengths. The results revealed significant differences in biological activity among the various series of conjugates. Particularly, 1A12C4 conjugates exhibited notably higher cytotoxicity compared to cyclen conjugates. Conjugation with 1A12C4 proved to be an effective strategy for increasing cellular uptake and cytotoxicity of small-molecule conjugates. In addition, the results highlighted the critical role of linker length in modulating the biological activity of DLM conjugates. It became clear that the choice of each component (dye, macrocycle and linker) could significantly alter the biological activity of the conjugates. [ABSTRACT FROM AUTHOR]

ABSTRACT: Thioxanthone–anthracene‐9‐carboxylic acid (TX‐ANCA) namely 14‐oxo‐14H‐naphthol [2,3‐b]thioxanten‐12‐carboxylic acid, is synthesized and characterized as part of our continuing interest for syntheses of polyaromatic initiators. Photoinitiator, TX‐ANCA have good absorption properties in the UV and visible region of the electromagnetic spectrum (ɛ370: 9080 M−1cm−1, ɛ430: 6151 M−1 cm−1). The fluorescence quantum yield is calculated as 0.1 which is slightly higher than of the parent thioxanthone compound (φf: 0.07). The phosphorescence lifetime is found to be 39 ms. The possible initiating mechanism of TX‐ANCA is based on photoexcitation of TX‐ANCA and quenching of triplet excited states of TX‐ANCA by molecular oxygen generates singlet oxygen. Singlet oxygen reacts with the anthracene moiety of TX‐ANCA possibly forms an endoperoxide. The endoperoxides undergoes photochemical or thermal decomposition to form radicals which are able to initiate free radical polymerization. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1878–1883 [ABSTRACT FROM AUTHOR]

Today, polymeric photoinitiators are good choice for initiation mechanism of UV-curable printing inks with their low migration potential. In this study, new thioxanthone-styrene polymeric photoinitiators were synthesized. Polystyrene that was synthesized by atom transfer radical polymerization (ATRP) was functionalized by cyclohexeneoxide and then reacted with thioxanthone-thioacetic acid. Piperazine was reacted with bromine chain end of polystyrene and final polymeric photoinitiator was obtained. Proton Nuclear Magnetic Resonance ( 1 H NMR), Attenuated Total Reflectance- Fourier Transform Infrared Spectroscopy (ATR-FTIR), Gel Permeation Chromatography (GPC) and Ultraviolet-Visible Spectroscopy (UV–vis) analyses were confirmed the expected structures. The curing property of new polymeric photoinitiator was compared with a conventional thioxanthone printing formulation that is used in flexographic varnish. The photopolymerization kinetics were determined by Photo Differential Scanning Calorimetry (Photo-DSC) and the results showed that 83% of conversion was reached for thioxanthone-styrene polymeric photoinitiator with MW = 4200. The migration behavior was identified with Liquid Chromatography–Mass Spectrometry LC–MS. It was shown that thioxanthone based polymeric photoinitiator is usable in flexographic varnish and thioxanthone migration level is reduced with macrophotoinitiation. [ABSTRACT FROM AUTHOR]

Self-assembled silver nanoparticles (Ag NPs) on calf thymus DNA (ct-DNA) chains were synthesized in the presence of 2-mercaptothioxanthone (TX-SH) by use of UV irradiation technique. Thioxanthone itself and its derivatives show interesting photochemical and biological properties. The formation of Ag NPs on the ct-DNA was achieved with and without TX-SH as a thioxanthone derivative photoinitiator which played a photoreducing role for the formation of Ag NPs. The photoreducing reaction of Ag ions to Ag NPs was followed by UV–vis absorption spectroscopy. A new band was observed at 428 nm which was a good sign of the surface plasmon resonance (SPR) of Ag NPs. Fluorescence quenching was effectively observed depending on the irradiation time of the solution, possibly as a result of Ag NPs size. Particle size analysis and Scanning Electron Microscopy (SEM) imaging confirmed the size of the formed Ag NPs and silver nanoclusters (Ag NCs) effectively. In this study, we report for the first time the formation of self–assembled Ag NPs on ct-DNA in the presence of 2-mercaptothioxanthone by photoirradiation technique. TX-SH played two important roles; photoreducing and photostabilizing agent for the formation of Ag NCs on ct-DNA. Fluorophore character of synthesized Ag NPs on DNA may help to develop new techniques for biological and medical aspects. [ABSTRACT FROM AUTHOR]

Gout is one of the most severe health problems of the aged and is caused by high levels of uric acid in the blood. The inhibition of Xanthine oxidase (XO) is one strategy to retain gout disease. Oxygenated xanthones and derivatives have been shown many important biological activities. However, some xanthones have the small amount of nature and its sulfur analogs, thioxanthone has not been well studied in their bioactivity. A series of hydroxyxanthones and allylxanthones analogous 3-5 have been synthesized and screened for their anti-XO activity. Leads to the discovery of 2,4-diallyl-1,3-dihydroxythioxanthone (5b) as the most active inhibitor with IC50 = 0.69±0.02 mM. Consequent molecular docking analysis by AutoDock 4.2 indicated that the most active compound (5b) inhibits XO by accommodated at the binding site of Xanthine oxidase. [ABSTRACT FROM AUTHOR]

Four different 1-aminocyclohexanes bearing a tethered thioxanthone group in the 2-position were prepared. The synthesis commenced with the respective N-protected β-amino acids, the carboxyl group of which was employed for the introduction of the thioxanthone moiety. After construction of the thioxanthone and protecting group removal, the conversion of the amino group into the respective thiourea was accomplished by treatment with N-3,5-bis(trifluoromethyl) phenyl isothiocyanate and yielded the title compounds in which the thioxanthone resides in different spatial positions relative to the thiourea motif. Overall yields varied between 20-35%. [ABSTRACT FROM AUTHOR]

A silicone-thioxanthone (STX) visible light photoinitiator was prepared by the nucleophilic substitution reaction of 2-[(4-hydroxybenzyl)-(methyl)-amino]-9H-thioxanthen-9-one (TX-HB) and γ-chloropropylmethylpolysiloxane-co-dimethyl-polysiloxane (PSO-Cl). Its structure was confirmed by 1H NMR, 13C NMR, FTIR, UV-vis and GPC. The photopolymerization kinetics of 1, 6-Hexanedioldiacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA) initiated by STX confirmed that STX is an efficient photoinitiator. Its visible light photolysis experiment and the photopolymerization kinetics studies implied that a possible synergistic effect existed between two adjacent thioxanthone groups. Moreover, a higher migration stability was revealed in STX than 2-benzyl (methyl) amino-9H-thioxanthen-9-one (TX-B). STX could change the surface property of the cured film of polyurethane diacrylate prepolymer (PUA) from hydrophilic to hydrophobic, as well as change the thermal stability of the polymer network. Meanwhile, it could improve the resistance against water and acid. Thus, STX is an effective multifunctionalized photoinitiator.

ABSTRACT Two one-component, double-chromophoric thioxanthone photoinitiators, namely TX-EDA and TX-DETA were synthesized by the reaction of thioxanthone aldehyde (TX-A) with ethylenediamine (EDA) and diethylenetriamine (DETA), respectively via a facile Schiff base reaction. Both photoinitiators were characterized by spectral analysis and photobleaching studies. DFT calculations are employed to reveal the contribution of the different orbitals to the excitation of the initiators. The double-chromophoric nature of the initiators gives rise to an increased absorption in the near UV region when compared with the pristine TX-A. Photoinitiated polymerization of various vinyl monomers with TX-EDA and TX-DETA has been investigated in the presence and absence of a co-initiator and compared for formulations consisting of precursor TX-A. In addition, real-time FTIR spectroscopic studies were performed in methyl methacrylate polymerization with both initiators. The higher efficiency observed with TX-DETA may be attributed to the additional hydrogen donating sites adjacent to nitrogen atoms. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3475-3482 [ABSTRACT FROM AUTHOR]

A novel kind of low migration one-component Type II photoinitiators was synthesized by Schiff base reaction of thioxanthone aldehyde and amine functional poly(propylene oxide) (PPO) precursors with two different molecular weights. The final initiators (TX-PPO) were characterized in detail by spectral analysis and DFT theoretical calculations. The molecular weight of the PPO directly effects the solubility of the initiator in monomers. The one-component photoinitiating nature of the initiators was demonstrated by photobleaching and photo polymerization of several vinyl monomers in the absence of a hydrogen donor such as triethylamine. Leaching studies on the photocured polymer films show only negligible migration of the photoinitiator. [ABSTRACT FROM AUTHOR]

Photobase generator (PBG)-mediated thiol-epoxy photopolymerization has received widedspread attention due to its versatility in various applications. Currently, nearly all reported PBGs release amines as active species. The formed amines induce odor, yellowing, and potential toxicity. In this study, a series of novel thioxanthone-based PBGs, which were able to generate carbanion via decarboxylation under LED light irradiation, were designed and straightforwardly prepared. The formed carbanion can be used as a superbase to catalyze thiol-epoxy polymerization efficiently. Investigation on ¹H NMR and FT-IR confirmed the generation of carbanion intermediates. The counteranion significantly affected the photodecarboxylation efficiency. The study of photopolymerization tests, based on real-time FT-IR and dielectric analysis measurements, indicated that the generated carbanion exhibited faster polymerization rate and higher epoxy conversion than traditional superbase 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). In differential scanning calorimeter, thermogravimetric, and nanoindentation tests, comparable thermal and mechanical properties of the photocured films catalyzed by novel PBGs were obtained. The high initiation ability combined with straightforward synthesis makes these PBGs promising candidates for commercialization. [ABSTRACT FROM AUTHOR]

Two thioxanthone based acrylated one-component visible light photoinitiators, 2-(methyl(4-((methyl(9-oxo-9H-thioxanthen-2-yl)amino)methyl)benzyl)amino)ethyl acrylate (TX-EA) and ((4-((methyl(9-oxo-9H-thioxanthen-2-yl)amino)methyl)benzyl)azanediyl)bis(ethane-2,1-diyl)diacrylate (TX-BDA), are designed and synthesized. The results of photopolymerization and migration study demonstrate that TX-EA and TX-BDA are more effective one-component visible light photoinitiators for free radical polymerization with excellent migration stability than 4-((methyl(9-oxo-9H-thioxanthen-2-yl)amino)methyl)phenyl acrylate. The mass fraction of the extracted TX-BDA in a cured 1,6-hexanediol diacrylate polymer film is as low as 0.55% and the residual amount is estimated to be only 90 ppm. TX-BDA would have great potential to be used in visible light curing systems, particularly in the food packing or biomedical fields. Results demonstrate that the synergistic effect of hydrogen donors and polymerizable groups in photoinitiator plays an important role in realizing high performance and low migration in photopolymerization system. [ABSTRACT FROM AUTHOR]

Photoinitiators for free radical polymerization based on the thioxanthone chromophore that contains benzothiophene were synthesized and characterized. Compared to thioxanthone, these compounds show a bathochromic shifted absorption up to ∼460 nm. High quantum yields for intersystem crossing generate sufficient amounts of triplet states. Initiator radicals are generated by reaction of the triplet states with tertiary amines, such as diethanolamine with high rate constants (2–6 × 10 9 M −1 s −1 ) as determined by laser flash photolysis. Photoinitiated polymerization experiments of MMA showed efficient polymerization with initiator concentrations as low as 0.1 mM. [ABSTRACT FROM AUTHOR]

Nowadays, the use of macromolecular photoinitiators provides for a good compatibility of the initiator in the formulation. Moreover, the migration of the initiator to the surface of the material is prevented, which results in low-odor and non-toxic coatings. In the present study, it has been demonstrated that polyvinylchloride macrophotoinitiator (PVC-TX) containing side chain thioxanthone (2%) moieties were successfully prepared by 'click chemistry'. For this purpose, propargyl thioxanthone and polyvinylchloride with side chain azide moieties were reacted in N,N-dimethylformamide for 24 hours at 25°C in order to give corresponding macrophotoinitiator. The synthesized polymer was characterized by 1H-NMR (nuclear magnetic resonance), UV (ultraviolet) and fluorescence spectroscopies and water based gel permeation chromatography. Obtained macrophotoinitiator has similar absorption characteristics compared to parent thioxanthone. Its capabilities to act as initiator for the photopolymerization of methacrylic acid, methyl methacrylate, N-vinyl pyrrolidone and styrene in various solvents in the absence and presence of triethylamine media were also examined.

In the present work, a theoretical study on the deactivation of triplet excited (T1) state thioxanthone (TX) by indole (INH) was performed, based on density functional theory calculations. Three feasible pathways, namely direct electron transfer from INH to T1 state TX, electron transfer followed by proton transfer from INH·+ to TX·– , and H-atom transfer from nitrogen of INH to keto oxygen of T1 state TX, were proposed theoretically to be involved in T1 state TX deactivation by INH.

ABSTRACT The photochemical and photophysical properties of new polymeric photoinitiators (PPIs) containing pendant thioxanthone (TX) and amine moieties are studied. The PPIs are synthesized by copolymerization of tert-butyl 2-((9-oxo-9H-thioxanthen-2-yloxy)methyl)acrylate (TX1) with N,N-dimethylaminoethyl methacrylate (DMAEM) at two different ratios using free radical polymerization. UV-vis spectra indicate that PPIs possess similar absorption characteristics to TX1 in the violet range (∼400 nm; absorption red-shift 20 nm). The photochemical mechanisms are studied by electron spin resonance (ESR), steady state photolysis, laser flash photolysis, and cyclic voltammetry. ESR studies indicate formation of two different aminoalkyl radicals on the hydrogen donor amine. The triplet state of the PPIs is short-lived compared to isopropyl thioxanthone and TX1, due to the built-in amine functionality. Photopolymerization of trimethylolpropane triacrylate (TMPTA) initiated by these photoinitiators under LED exposure at 385 and 405 nm using real-time FTIR spectroscopy shows that they exhibit higher efficiency than TX/ N-methyldiethanolamine (MDEA) and TX1/MDEA systems with the advantage of a much higher molecular weight that can be very helpful to overcome migration issues. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3370-3378 [ABSTRACT FROM AUTHOR]

A novel biopolymeric photoinitiator was synthetized from N -phthaloyl chitosan. The 10-oxo-10H-dibenzene thiopyran-3-4-dicarboximide/chitosan (TXICh) structure was characterized by 1D ( 1 H and 13 C) and 2D ( 1 H 1 H COSY, 1 H 13 C HSQC and 1 H 13 C HMBC) NMR experiments. TXICh showed absorption in a wide region of the visible, with bands at 385, 450 and 540 nm. Fluorescence measurements showed three emitting states with lifetimes of 3, 0.612 and 0.021 ns. Transient lifetimes of the same magnitude were found for TXICh by femtosecond time-resolved pump-probe transient absorption spectroscopy. TXICh triplet formation was observed by flash photolysis. This excited state is responsible for producing radicals, which initiate photopolymerization. The efficiency of TXICh as a biopolymeric photoinitiator was checked by photopolymerization kinetics of TEGDMA using photocalorimetry (photo-DSC). The ability and efficiency of TXICh to act as photoinitiator radical in different wavelengths was confirmed. [ABSTRACT FROM AUTHOR]

Three thioxanthone-based hydrophilic visible photoinitiators (TX-MPEG350, TX-MPEG550, and TX-MPEG750) are prepared and characterized. All of them exhibit excellent water dispersion properties. Real-time FTIR investigation shows that they can be used as visible photoinitiators for radical polymerization in waterborne systems in the presence and absence of the hydrogen donors. Among them, TX-MPEG550 has been illustrated as the best hydrophilic visible photoinitiator in the presence of hydrogen donors and would have great potential applications in waterborne visible photocuring systems after carefully investigating the photopolymerization behavior of TX-MPEGs in different conditions. [ABSTRACT FROM AUTHOR]

Five novel thioxanthone (TX)-functionalized methacrylates as copolymerizable photoinitiators (CopPIs) for polymerization of acrylates are synthesized from reactions of tert-butyl α-bromomethacrylate with 2-hydroxy thioxanthone (TX1) and 1,4-dihydroxy thioxanthone (TX3), cleavage of their respective tert-butyl ester groups with trifluoroacetic acid (TX2, TX4), and by reaction of the acid chloride derivative of TX2 with Irgacure 2959 (TX5). These CopPIs absorb in the near UV-visible region (390-420 nm; absorption redshift =10-40 nm, ε values comparable to TX). Their performances are studied under LED exposure at 385 and 405 nm using real-time FTIR. The reactivities of TX1 and TX2 are similar to isopropyl thioxanthone, used as reference; and TX4 have lower reactivities, due to their difunctionality, which however makes them good crosslinking agents. TX5 is the first monomeric PI possessing two different type side-chain photoinitiating groups. The migration stability of two of these CopPIs is shown in the cured polyacrylates. The photochemical mechanisms are studied by electron spin resonance, steady state photolysis, laser flash photolysis, and cyclic voltammetry. [ABSTRACT FROM AUTHOR]