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Article ; Online: Riboflavin and Eosin Y Supported on Chromatographic Silica Gel as Heterogeneous Photocatalysts.

Caminos, Daniel A / Rimondino, Guido N / Gatica, Eduardo / Massad, Walter A / Argüello, Juan E

ACS omega

2023 Volume 8, Issue 33, Page(s) 30705–30715

Abstract: The application of photocatalysis for organic synthesis, both in the laboratory and on an industrial scale, will depend on the achieving of good yields and the ease with which it can be applied. Selective irradiation of the photocatalyst with LED light ... ...

Abstract	The application of photocatalysis for organic synthesis, both in the laboratory and on an industrial scale, will depend on the achieving of good yields and the ease with which it can be applied. Selective irradiation of the photocatalyst with LED light has made it possible to activate the reactions easily, without the need for UV or heat filters. However, a common problem is the need to separate the photocatalyst from the reaction products through extraction and chromatography isolation processes. These procedures make it difficult to recover and reuse the catalyst, which is not compatible with scale-up applications. Photocatalysts attached to heterogeneous supports resulted in an alternative, which facilitates their removal and reuse. In this study, we use chromatographic silica gel as a low-cost heterogeneous support to bind photosensitizers such as Riboflavin or Eosin Y. The modified silica gel was analyzed by FTIR-ATR and diffuse reflectance UV-visible spectroscopy, thermogravimetric analysis, and optical microscopy. These hybrid materials have a suitable size for easy separation by decantation and were found to be photoactive against two photooxidation reactions. These easy-to-handle materials open the door to effective applications for photoinduced organic synthesis methods at medium to large scale.
Language	English
Publishing date	2023-08-09
Publishing country	United States
Document type	Journal Article
ISSN	2470-1343
ISSN (online)	2470-1343
DOI	10.1021/acsomega.3c04622
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Article: Anions involved in the initiation of the thermally induced SRN1 reaction for α-arylation of ketones

Caminos, Daniel A / Puiatti, Marcelo / Bardagí, Javier Ivan / Peñéñory, Alicia B

RSC advances. 2017 June 19, v. 7, no. 50

2017

Abstract: The SRN1 reaction between acetophenone enolate and PhI is thermally induced and accelerated by microwave irradiation to give the corresponding substitution product 1,2-diphenylethanone in a 50% yield in DMSO at 70 °C. Regarding the mechanism of ... ...

Abstract	The SRN1 reaction between acetophenone enolate and PhI is thermally induced and accelerated by microwave irradiation to give the corresponding substitution product 1,2-diphenylethanone in a 50% yield in DMSO at 70 °C. Regarding the mechanism of initiation, in this reaction, acetophenone enolate, tert-butoxyde anion and dimsyl anion (the ionic form of the solvent) could promote the initial electron transfer to start the radical reaction. Comparative studies on the PhI dehalogenation promoted by the different anions were conducted in DMSO under microwave irradiation and by quantum calculations. The dimsyl anion shows a higher iodide generation even at lower concentrations than acetophenone enolate and tBuO−. Likewise, DFT calculation by B3PW91, M062X and PBE0 shows the dymsyl anion to be the best electron donor. While the three anions can initiate the radical reaction, the reactivity order found locates the dimsyl anion in first place, followed by the enolate of acetophenone and then the alkoxide. The results reported herein allow a greater understanding of the initiation process with tert-butoxide solutions in DMSO.
Keywords	acetophenones ; anions ; dehalogenation ; dimethyl sulfoxide ; electron transfer ; microwave radiation ; solvents
Language	English
Dates of publication	2017-0619
Size	p. 31148-31157.
Publishing place	The Royal Society of Chemistry
Document type	Article
ISSN	2046-2069
DOI	10.1039/c7ra05156e
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Article: Microwave role in the thermally induced SRN1 reaction for α-arylation of ketones

Caminos, Daniel A / Garro, Alexis D / Peñéñory, Alicia B / Soria-Castro, Silvia M

RSC advances. 2015 Feb. 18, v. 5, no. 26

2015

Abstract: The coupling between iodobenzene and the enolate anion of acetophenone is accelerated by microwave irradiation. This increase in reaction rate is only ascribed to thermal effects. The coupling reaction gave the corresponding substitution product 1,2-di- ... ...

Abstract	The coupling between iodobenzene and the enolate anion of acetophenone is accelerated by microwave irradiation. This increase in reaction rate is only ascribed to thermal effects. The coupling reaction gave the corresponding substitution product 1,2-di-phenylethanone in a 50% yield when microwave irradiation was applied between 15–60 s according to the intensity of the pulse. Moreover, this reaction is effective in a temperature window of 70–120 °C. The presence of ionic and dipolar species is not involved in the initiation process as molecular radiators. The excess of tBuOK in the reaction medium may also act as an electron donor helping to generate radicals when the solution temperature increases to 70 °C.
Keywords	acetophenones ; arylation ; free radicals ; iodobenzenes ; microwave radiation ; temperature
Language	English
Dates of publication	2015-0218
Size	p. 20058-20065.
Publishing place	The Royal Society of Chemistry
Document type	Article
ISSN	2046-2069
DOI	10.1039/c4ra17055e
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Article: A simple experiment to show photodynamic inactivation of bacteria on surfaces.

Caminos, Daniel A / Durantini, Edgardo N

Biochemistry and molecular biology education : a bimonthly publication of the International Union of Biochemistry and Molecular Biology

2007 Volume 35, Issue 1, Page(s) 64–69

Abstract: New suitable approaches were investigated to visualize the photodynamic inactivation (PDI) of bacteria immobilized on agar surfaces. The PDI capacities of a cationic photosensitizer (5,10,15,20-tetra(4-N,N,N-trimethylammoniumphenyl)porphyrin) and an ... ...

Abstract	New suitable approaches were investigated to visualize the photodynamic inactivation (PDI) of bacteria immobilized on agar surfaces. The PDI capacities of a cationic photosensitizer (5,10,15,20-tetra(4-N,N,N-trimethylammoniumphenyl)porphyrin) and an anionic photosensitizer (5,10,15,20-tetra(4-sulfonatophenyl)porphyrin) were analyzed on a typical Gram-negative bacterium Escherichia coli following two procedures. In Experiment I, the E. coli cells were grown as lawn on agar surface containing the sensitizers spread in a small area (10 nmol in ∼0.6 cm(2) ). After irradiation with visible light (10 min, 90 milliwatts/cm(2) ), no cells were grown in the area containing the cationic porphyrin. In Experiment II, small colonies (∼2-mm diameter) of E. coli on agar were treated with a solution of sensitizer (10 nmol) and irradiated with visible light for 3 h. Overnight incubation at 37 °C shows a growth delay of E. coli colonies treated with the cationic photosensitizer. In contrast, the anionic porphyrin did not produce appreciable photodamage. These experiments could be either used in an undergraduate project for natural science advance students or used for a postgraduate practical training course. This methodology illustrates the application of PDI to treat bacteria growing as localized foci of infection.
Language	English
Publishing date	2007-01
Publishing country	United States
Document type	Journal Article
ISSN	1470-8175
ISSN	1470-8175
DOI	10.1002/bmb.11
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Article: An expedient route to heterocycles through α-arylation of ketones and arylamides by microwave induced thermal SRN1 reactions

Soria-Castro, Silvia M / Caminos, Daniel A / Peñéñory, Alicia B

RSC advances. 2014 Apr. 10, v. 4, no. 34

2014

Abstract: Microwave irradiation promotes a quick aromatic nucleophilic substitution by a thermally induced electron transfer process to form new C–C bonds by the coupling of aryl radicals and enolate nucleophiles. Diverse 2-aryl-1-phenylethanones can be prepared ... ...

Abstract	Microwave irradiation promotes a quick aromatic nucleophilic substitution by a thermally induced electron transfer process to form new C–C bonds by the coupling of aryl radicals and enolate nucleophiles. Diverse 2-aryl-1-phenylethanones can be prepared by the direct α-arylation of acetophenone with different haloarenes. The ketone enolate anion is generated by deprotonation with tBuOK in DMSO and the reaction is carried out in a closed microwave vessel at 70–100 °C for 10 min. This simple procedure also allows the synthesis of deoxybenzoin and indole heterocycle derivatives by inter- or intra-molecular ring closure reactions, with moderate to excellent substitution yields.
Keywords	acetophenones ; aromatic compounds ; arylation ; chemical bonding ; deprotonation ; dimethyl sulfoxide ; electron transfer ; free radicals ; indoles ; Lewis bases ; microwave radiation
Language	English
Dates of publication	2014-0410
Size	p. 17490-17497.
Publishing place	The Royal Society of Chemistry
Document type	Article
ISSN	2046-2069
DOI	10.1039/c4ra00120f
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Article: Photodynamic inactivation of Escherichia coli immobilized on agar surfaces by a tricationic porphyrin.

Caminos, Daniel A / Durantini, Edgardo N

Bioorganic & medicinal chemistry

2006 Volume 14, Issue 12, Page(s) 4253–4259

Abstract: The photodynamic activity of 5,10,15-tris[4-(3-N,N,N-trimethylammoniumpropoxy)phenyl]-20-(4-trifluoromethylphenyl)porphyrin iodide (A3B3+) has been studied in vitro on a typical Gram-negative bacterium Escherichia coli immobilized on agar surfaces. The ... ...

Abstract	The photodynamic activity of 5,10,15-tris[4-(3-N,N,N-trimethylammoniumpropoxy)phenyl]-20-(4-trifluoromethylphenyl)porphyrin iodide (A3B3+) has been studied in vitro on a typical Gram-negative bacterium Escherichia coli immobilized on agar surfaces. The results obtained for the tricationic A3B3+ porphyrin were compared with those of 5,10,15,20-tetra(4-N,N,N-trimethylammoniumphenyl)porphyrin p-tosylate (TTAP4+), which is a standard active sensitizer established to eradicate E. coli in cellular suspension. The photobleaching of these porphyrins in solution was evaluated by decay in absorbance and in fluorescence. In both cases, a higher photostability was found for A3B3+ than for TTAP4+. Photodynamic inactivation capacities of these sensitizers were analyzed in E. coli cells immobilized on agar surfaces. Small colonies were treated with different amount of sensitizer (0-14 nmol) and irradiated with visible light for 3h. The light source used was either a projector or midday sun. The A3B3+ porphyrin produced a growth delay of E. coli colonies on agar surfaces. Similar result was obtained irradiating only one isolated colony through an optical fiber. Under these conditions, A3B3+ porphyrin shows a high activity to inactivate localized bacterial cells. The higher photodynamic activity of A3B3+ was confirmed by mechanical spreading of the colonies before treatment. This procedure produces complete inactivation of E. coli cells on the agar surface. Therefore, tricationic A3B3+ porphyrin is an interesting sensitizer with potential applications in photodynamic inactivation of bacteria growing as localized foci of infection.
MeSH term(s)	Agar/chemistry ; Cations/chemistry ; Cations/pharmacology ; Cells, Immobilized/drug effects ; Cells, Immobilized/radiation effects ; Escherichia coli/cytology ; Escherichia coli/drug effects ; Escherichia coli/radiation effects ; In Vitro Techniques ; Light ; Microbial Sensitivity Tests ; Molecular Structure ; Photosensitizing Agents/chemistry ; Photosensitizing Agents/pharmacology ; Porphyrins/chemistry ; Porphyrins/pharmacology ; Structure-Activity Relationship ; Surface Properties
Chemical Substances	5,10,15,20-tetera(4-N,N,N-trimethylammoniumphenyl)porphyrin 4-tosylate ; 5,10,15-tris(4-(3--N,N,N-trimethylammoniumpropoxy)phenyl)-20-(4-trifluoromethylphenyl)porphyrin ; Cations ; Photosensitizing Agents ; Porphyrins ; Agar (9002-18-0)
Language	English
Publishing date	2006-06-15
Publishing country	England
Document type	Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	1161284-8
ISSN	1464-3391 ; 0968-0896
ISSN (online)	1464-3391
ISSN	0968-0896
DOI	10.1016/j.bmc.2006.01.058
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Article ; Online: Mechanistic Insight into the Cu-Catalyzed C-S Cross-Coupling of Thioacetate with Aryl Halides: A Joint Experimental-Computational Study.

Soria-Castro, Silvia M / Andrada, Diego M / Caminos, Daniel A / Argüello, Juan E / Robert, Marc / Peñéñory, Alicia B

The Journal of organic chemistry

2017 Volume 82, Issue 21, Page(s) 11464–11473

Abstract: The mechanism of the Ullmann-type reaction between potassium thioacetate (KSAc) and iodobenzene (PhI) catalyzed by CuI associated with 1,10-phenanthroline (phen) as a ligand was explored experimentally and computationally. The study on C-S bond formation ...

Abstract	The mechanism of the Ullmann-type reaction between potassium thioacetate (KSAc) and iodobenzene (PhI) catalyzed by CuI associated with 1,10-phenanthroline (phen) as a ligand was explored experimentally and computationally. The study on C-S bond formation was investigated by UV-visible spectrophotometry, cyclic voltammetry, mass spectrometry, and products assessment from radical probes. The results indicate that under experimental conditions the catalytically active species is [Cu(phen)(SAc)] regardless of the copper source. An examination of the aryl halide activation mechanism using radical probes was undertaken. No evidence of the presence of radical species was found during the reaction process, which is consistent with an oxidative addition cross-coupling pathway. The different reaction pathways leading to the experimentally observed reaction products were studied by DFT calculation. The oxidative addition-reductive elimination mechanism via an unstable Cu
Language	English
Publishing date	2017-11-03
Publishing country	United States
Document type	Journal Article
ZDB-ID	123490-0
ISSN	1520-6904 ; 0022-3263
ISSN (online)	1520-6904
ISSN	0022-3263
DOI	10.1021/acs.joc.7b01991
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Article ; Online: Mechanistic insight of the photodynamic inactivation of Escherichia coli by a tetracationic zinc(II) phthalocyanine derivative.

Spesia, Mariana B / Caminos, Daniel A / Pons, Patricia / Durantini, Edgardo N

Photodiagnosis and photodynamic therapy

2009 Volume 6, Issue 1, Page(s) 52–61

Abstract: Photodynamic inactivation (PDI) of Escherichia coli has been studied in cultures treated with zinc(II) 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]phthalocyanine (ZnPPc(+4)) to obtain insight about the mechanism of damage. This phthalocyanine is rapidly ... ...

Abstract	Photodynamic inactivation (PDI) of Escherichia coli has been studied in cultures treated with zinc(II) 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]phthalocyanine (ZnPPc(+4)) to obtain insight about the mechanism of damage. This phthalocyanine is rapidly bound to cells, reaching a value of approximately 0.8 nmol/10(6) cells when the cultures were incubated with 2 microM sensitizer. After 30 min of irradiation, a 4 log decrease of E. coli survival was observed. The photocytotoxic action was investigated in plasmid and genomic DNA by electrophoretic analysis. Absorption spectroscopic studies showed that this cationic phthalocyanine interacts strongly with DNA (K(DNA)=4.7 x 10(6)M(-1)). Photocleavage of calf thymus DNA sensitized by ZnPPc(+)4 was not found even after long irradiation periods. Similar results were also observed in genomic DNA extracted from E. coli cells after PDI treatment. Modifications of plasmid DNA isolated from bacteria were only observed after long irradiation periods. However, under these conditions transmission electron microscopy of the PDI bacteria revealed an aggregation of cytoplasmic macromolecules and irregularities in cell barriers. Also, scanning electron microscopy showed a shrunken appearance in cells after PDI. Even so, release of intracellular biopolymers was not detected by absorption. On the other hand, outer and inner membranes permeabilization assays showed an increase in the permeability. Consequently, alterations in the cell membrane functionality induced by ZnPPc(+4) appear to be the major cause of E. coli inactivation upon PDI.
MeSH term(s)	Cations ; Cell Survival/drug effects ; Cell Survival/radiation effects ; Dose-Response Relationship, Drug ; Dose-Response Relationship, Radiation ; Escherichia coli/drug effects ; Escherichia coli/radiation effects ; Indoles/administration & dosage ; Indoles/chemistry ; Light ; Organometallic Compounds/administration & dosage ; Organometallic Compounds/chemistry ; Photochemotherapy/methods ; Photosensitizing Agents/administration & dosage ; Photosensitizing Agents/chemistry ; Radiation Dosage
Chemical Substances	Cations ; Indoles ; Organometallic Compounds ; Photosensitizing Agents ; Zn(II)-phthalocyanine (14320-04-8)
Language	English
Publishing date	2009-03
Publishing country	Netherlands
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2149918-4
ISSN	1873-1597 ; 1572-1000
ISSN (online)	1873-1597
ISSN	1572-1000
DOI	10.1016/j.pdpdt.2009.01.003
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Article: Photodynamic inactivation of Escherichia coli by novel meso-substituted porphyrins by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl and 4-(trifluoromethyl)phenyl groups.

Caminos, Daniel A / Spesia, Mariana B / Durantini, Edgardo N

Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology

2006 Volume 5, Issue 1, Page(s) 56–65

Abstract: The photodynamic effect of novel cationic porphyrins, with different pattern of meso-substitution by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, have been studied in both solution bearing photooxidizable ... ...

Abstract	The photodynamic effect of novel cationic porphyrins, with different pattern of meso-substitution by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, have been studied in both solution bearing photooxidizable substrates and in vitro on a typical Gram-negative bacterium Escherichia coli. In these sensitizers, the cationic groups are separated from the macrocycle ring by a propoxy spacer. Thus, the charges have a high mobility and a minimal influence on photophysical properties of the porphyrin. These compounds produce singlet molecular oxygen, O2(1Delta(g)), with quantum yields of approximately 0.41-0.53 in N,N-dimethylformamide. In methanol, the l-tryptophan photodecomposition increases with the number of cationic charges in the sensitizer. In vitro investigations show that cationic porphyrins are rapidly bound to E. coli cells in approximately 5 min. A higher binding was found for A3B3+ porphyrin, which is tightly bound to cells still after three washing steps. Photosensitized inactivation of E. coli cellular suspensions follows the order: A3B3+ > A44+>> ABAB2+ > AB3+. Under these conditions, a negligible effect was found for 5,10,15,20-tetra(4-sulfonatophenyl)porphyrin (TPPS4(4-)) that characterizes an anionic sensitizer. Also, the results obtained for these new cationic porphyrins were compared with those of 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin (TTAP4+), which is a standard active sensitizer established to eradicate E. coli. The photodynamic activity of TTAP4+ is quite similar to that produced by A4(4+). Studies in an anoxic condition indicate that oxygen is necessary for the mechanism of action of photodynamic inactivation of bacteria. The higher photodynamic activity of A3B3+ was confirmed by growth delay experiments. Photodynamic inactivation capacities of these sensitizers were also evaluated in E. coli cells immobilized on agar surfaces. Under these conditions, A3B3+ porphyrin retains a high activity to inactivate localized bacterial cells. Therefore, tricationic porphyrin A3B3+ is an interesting sensitizer with potential applications in photodynamic inactivation of bacteria in liquid suspensions or on surfaces.
MeSH term(s)	Benzene Derivatives/chemistry ; Cell Survival/drug effects ; Cell Survival/radiation effects ; Cells, Cultured ; Escherichia coli/cytology ; Escherichia coli/drug effects ; Escherichia coli/radiation effects ; Light ; Microbial Sensitivity Tests ; Molecular Structure ; Photosensitizing Agents/chemistry ; Photosensitizing Agents/pharmacology ; Porphyrins/chemistry ; Porphyrins/pharmacology ; Spectrometry, Fluorescence ; Structure-Activity Relationship
Chemical Substances	Benzene Derivatives ; Photosensitizing Agents ; Porphyrins
Language	English
Publishing date	2006-01
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2072584-X
ISSN	1474-9092 ; 1474-905X
ISSN (online)	1474-9092
ISSN	1474-905X
DOI	10.1039/b513511g
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Article: Mechanisms of Escherichia coli photodynamic inactivation by an amphiphilic tricationic porphyrin and 5,10,15,20-tetra(4-N,N,N-trimethylammoniumphenyl) porphyrin.

Caminos, Daniel A / Spesia, Mariana B / Pons, Patricia / Durantini, Edgardo N

Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology

2008 Volume 7, Issue 9, Page(s) 1071–1078

Abstract: The mechanistic aspects of Escherichia coli photodynamic inactivation (PDI) have been investigated in bacteria treated with 5,10,15-tris[4-(3-N,N,N-trimethylammoniumpropoxy)phenyl]-20-(4-trifluoromethylphenyl)porphyrin iodide (A3B3+) and visible light. ... ...

Abstract	The mechanistic aspects of Escherichia coli photodynamic inactivation (PDI) have been investigated in bacteria treated with 5,10,15-tris[4-(3-N,N,N-trimethylammoniumpropoxy)phenyl]-20-(4-trifluoromethylphenyl)porphyrin iodide (A3B3+) and visible light. The photosensitization activity of A3B3+ porphyrin was compared with that of 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin p-tosylate (TMAP4+), which is an active tetracationic sensitizer to eradicate bacteria. The PDI damages on plasmid and genomic DNA were analyzed by electrophoresis. DNA photocleavage was observed after a long period of irradiation, when the bacterial cells are largely photoinactivated. Transmission electron microscopy (TEM) revealed structural changes with appearance of low density areas into the cells and irregularities in cell barriers, which could affect the normal cell membrane functionality. Also, damages on the cell-wall were not detected by scanning electron microscopy (SEM) and release of intracellular biopolymers was not found after PDI. These results indicate that the photodynamic activity of these cationic porphyrins produces DNA photodamage after a long period of irradiation. Therefore, an interference with membrane functions could be the main cause of E. coli photoinactivation upon short PDI treatments.
MeSH term(s)	Cations/chemistry ; Cell Membrane/drug effects ; Cell Membrane/radiation effects ; Escherichia coli/drug effects ; Escherichia coli/radiation effects ; Escherichia coli/ultrastructure ; Hydrophobic and Hydrophilic Interactions ; Methylation ; Microbial Viability/radiation effects ; Microscopy, Electron, Scanning ; Microscopy, Electron, Transmission ; Molecular Structure ; Photochemistry ; Porphyrins/chemistry ; Porphyrins/pharmacology ; Quaternary Ammonium Compounds/chemistry ; Water/chemistry
Chemical Substances	Cations ; Porphyrins ; Quaternary Ammonium Compounds ; Water (059QF0KO0R)
Language	English
Publishing date	2008-09
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2072584-X
ISSN	1474-9092 ; 1474-905X
ISSN (online)	1474-9092
ISSN	1474-905X
DOI	10.1039/b804965c
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