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Physical-Chemical Study of Anthracene Selective Oxidation by a Fe(III)-Phenylporhyrin Derivative

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Physical-Chemical Study of Anthracene Selective Oxidation by a Fe(III)-Phenylporhyrin Derivative International Journal of Molecular Sciences Article Physical-Chemical Study of Anthracene Selective Oxidation by a Fe(III)-Phenylporhyrin Derivative Carlos Diaz-Uribe 1, William Vallejo 1,* and Cesar Quiñones 2 1 Grupo de Fotoquímica y Fotobiología, Universidad del Atlántico, Puerto Colombia 81007, Colombia; [email protected] 2 Facultad de Ingeniería Diseño e Innovación, Politécnico Grancolombiano, Bogotá 110231, Colombia; [email protected] * Correspondence: [email protected]; Tel.: +57-5-3599484 Received: 30 October 2019; Accepted: 3 January 2020; Published: 5 January 2020 Abstract: In this work, we studied the anthracene oxidation by hydroxyl radicals. Hydroxyl radical was generated by reaction of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin Fe (III) (TPPFe) with hydrogen peroxide under visible radiation at a nitrogen atmosphere. The TPPFe was synthesized by Adler Method followed by metal complexation with Fe (III) chloride hexahydrate. Hydroxyl radical was detected by fluorescence emission spectroscopy and we studied kinetic of anthracene selective oxidation by hydroxyl radicals through the differential method. The TPPFe was characterized by UV-Vis spectrophotometry, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) measurements. The results indicated that TPPFE was compound by micro-particles with a size distribution of around 2500 nm. Kinetic results showed that the apparent rate constant for the oxidation of anthracene increased exponentially on as temperature increases, furthermore, the activation energy for the Anthracene oxidation by hydroxyl radicals under visible irradiation was 51.3 kJ/mol. Finally, anthraquinone was the main byproduct generated after oxidation of anthracene by TPP-Fe under visible irradiation. Keywords: sensitizer; porphyrin; hydroxyl radical; polycyclic aromatic hydrocarbons; anthracene 1. Introduction Nowadays polycyclic aromatic hydrocarbons (PAH) originate from the incomplete combustion of fossil fuels are an important researching subject, from the environmental point of view, PAH are very important since they are involved in metabolic processes that affect human health [1,2]. Reactive oxygen species (ROS) are an emerging class of endogenous, highly reactive, oxygen molecules, these species can originate oxidation reactions of PAH, main ROS involve singlet oxygen and oxygen free radicals such as hydroxyl radical (HO•), superoxide anion (O2−•), hydroperoxyl (HOO•) or other similar radicals [3,4]. Specific photodynamic oxidation reactions have become an alternative methodology for PAH oxidation; the complex primary photochemical reaction processes due to an interaction of a photosensitizer with visible light could generate several reactive oxygen species in the reaction 1 medium ( O2,O•, HO•)[5,6]. Hydroxyl radical can be achieved through different methodologies: (a) chemical trapping, (b) laser flash photolysis, (c) pulse radiolysis, and (d) laser-induced fluorescence. Hydroxyl radical reaction to PHS (e.g., Naphthalene, Biphenyl, Anthracene) is reported for ROS detection in solution [7]. F. Goulay et al., reported the first direct measurement of the reaction rate constant of a polycyclic aromatic hydrocarbon in the gas phase in the temperature range 58–470 K [8]. Different factors involve in ROS generation: photo-sensitizers, electromagnetic radiation and 3 the molecular oxygen O2. Under visible light irradiation, the photosensitizer (PS) excites from basal state (oPS) to singlet state (1PS*) after that, 1PS* could decay to triplet state (3PS*) through internal Int. J. Mol. Sci. 2020, 21, 353; doi:10.3390/ijms21010353 www.mdpi.com/journal/ijms Int. J. Mol. Sci. 2020, 21, x FOR PEER REVIEW 2 of 11 (oInt.PS) J. to Mol. singlet Sci. 2020 state, 21, 353(1PS*) after that, 1PS* could decay to triplet state (3PS*) through internal cross-2 of 11 system process; in this stage 3PS* could produce radical species as hydroxyl or superoxide radicals throughcross-system electron process; transfer in this reaction, stage 3 thisPS* kind could of produce reaction radical is known species as type as hydroxyl I [9]. Many or superoxide compounds radicals have beenthrough reported electron as sensitizers transfer reaction, (e.g., porphyrin, this kind of ph reactionthalocyanines, is known and as typetheir I metal [9]. Many derivatives), compounds among have these,been reportedporphyrins as sensitizers their metalcomplexes (e.g., porphyrin, are phthalocyanines, macrocyclic molecules and their with metal an derivatives), extensive amongdelocalized these, electronsporphyrins system, their metalcomplexesthey have electronic are macrocyclic and optica moleculesl properties, with anapplied extensive in delocalizedfields like artificial electrons photodynamicsystem, they have therapy, electronic solar and cells optical and properties, photocatal appliedysis in[10–12], fields like furtherm artificialore, photodynamic metalloporphyrin therapy, derivativessolar cells andhave photocatalysis reported as [hydroxyl10–12], furthermore, radical generators, metalloporphyrin however, derivatives knowledge have about reported kinetic as informationhydroxyl radical is few; generators, about this however, topic, a knowledgedetailed knowledge about kinetic of oxidation information mechanisms is few; about initiated this topic, by molecular oxygen and OH• radicals is important to optimization of experimental conditions [13]. It a detailed knowledge of oxidation mechanisms initiated by molecular oxygen and OH• radicals is isimportant known that to optimization the efficient ofphoto-activity experimental of conditions both the [13simple]. It is porphyrins known that and the ethefficient metal photo-activity complexes porphyrinsof both the simpleis due to porphyrins their capability and the to metal produce complexes either superoxide porphyrins anion is due radical to their or capability singlet oxygen to produce by typeeither I and superoxide type II processes, anion radical respectively; or singlet oxygen for which bytype the type I and II type process II processes, is thought respectively; to be dominant for which in freethe base type porphyrin II process [14]. is thought Selective to oxidation be dominant of anthracene in free base to anthraquinone porphyrin [14]. before Selective by reaction oxidation with of aceticanthracene acid [15] to anthraquinoneand metachloroperbenzoic before by reaction acid by with electron-withdrawing acetic acid [15] and metachloroperbenzoic metalloporphyrins [16] acid has by beenelectron-withdrawing reported. metalloporphyrins [16] has been reported. ConsideringConsidering the adverseadverse e ffeffectsects on environmentson environments and humanand human health ofhealth PAH, of we PAH, selected we anthracene selected anthraceneas the target as in the this target work in because this work of the because anthracene of the is anthracene considering is one considering of the 16 priority one of PAHsthe 16 indicatedpriority PAHsby the indicated US environmental by the US environmental protection agency protection (EPA) agency [17]. There (EPA) are [17]. reports There concerning are reports toconcerning oxidation to oxidation of anthracene with free radicals NO3•, OH• and SO4•− [18–21]. Furthermore, the formation of anthracene with free radicals NO3•, OH• and SO4•− [18–21]. Furthermore, the formation of of nitro-anthracene from the degradation of anthracene by the OH• and NO3• has been investigated nitro-anthracene from the degradation of anthracene by the OH• and NO3• has been investigated usingusing quantum quantum chemical chemical calculations calculations [22,23]. [22,23]. Karan Karan et et al. al. reported reported the the photocatalytic photocatalytic degradation degradation of of anthracene under UV irradiation on TiO2 nanoparticles, they found that the main product of anthracene under UV irradiation on TiO2 nanoparticles, they found that the main product of oxidation oxidationof Anthracene of Anthracene is 9,10-Anthraquinone, is 9,10-Anthraquinone, which is safer wh forich theis safer environment for the environment than Anthracene than [ 24Anthracene]. Kozak et [24]. Kozak et al. removed PAHs from the pretreated coking wastewater by using CaO2, Fenton al. removed PAHs from the pretreated coking wastewater by using CaO2, Fenton reagent under reagentUV irradiation under UV [25 irradiation]. The applications [25]. The applications of Fenton oxidationof Fenton ofoxidation different ofPAH different have PAH been have shown been to shownhave great to have potential great potential (e.g., photo-Fenton, (e.g., photo-Fenton, sono-Fenton sono-Fenton and electro-Fenton and electro-Fenton [26–29]). [26–29]). Fenton reactionFenton reaction mechanism relies on OH• generation by the reaction of a ferrous ion with hydrogen peroxide mechanism relies on OH• generation by the reaction of a ferrous ion with hydrogen peroxide (H2O2) (Hthis2O mechanism2) this mechanism is useful is touseful break to down break a didownfferent a different organic compound. organic compound. The Scheme The1 shows Scheme the 1 generalshows thereaction general for reaction Fenton for reaction. Fenton reaction. Fe2+ Fe3+ H2O2 OH• SchemeScheme 1. 1. OHOH• •generationgeneration by by Fenton Fenton reaction. reaction. TheThe photo photo Fenton Fenton reaction reaction has has been been already already used used to to degrade degrade samples samples of of phenol phenol [30,31]. [30,31]. The The rate rate ofof this this reaction reaction could could be be increased increased when when
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