Immobilized lignin peroxidase-like metalloporphyrins as reusable catalysts in oxidative bleaching of industrial dyes

Synthetic and bioinspired metalloporphyrins are a class of redox-Active catalysts able to emulate several enzymes such as cytochromes P450, ligninolytic peroxidases, and peroxygenases. Their ability to perform oxidation and degradation of recalcitrant compounds, including aliphatic hydrocarbons, phenolic and non-phenolic aromatic compounds, sulfides, and nitroso-compounds, has been deeply investigated. Such a broad substrate specificity has suggested their use also in the bleaching of textile plant wastewaters. In fact, industrial dyes belong to very different chemical classes, being their effective and inexpensive oxidation an important challenge from both economic and environmental perspective. Accordingly, we review here the most widespread synthetic metalloporphyrins, and the most promising formulations for large-scale applications. In particular, we focus on the most convenient approaches for immobilization to conceive economical affordable processes. Then, the molecular routes of catalysis and the reported substrate specificity on the treatment of the most diffused textile dyes are encompassed, including the use of redox mediators and the comparison with the most common biological and enzymatic alternative, in order to depict an updated picture of a very promising field for large-scale applications

Covalent and noncovalent hybrids of di-amino porphyrin functionalized graphene oxide and their interaction with gold nanoparticles

Porphyrin functionalization of graphene oxide (GO) influenced the plasmonic effect of gold nanoparticles (AuNP). The former was achieved by modification of GO with 5,10-bis(4-aminophenyl)-15,20-diphenylpor-phyrin, P(NH2)2,adj, by noncovalent interactions as well as by covalent association, following standard chemis-try. The success of the chemical functionalization of GO with P(NH2)2,adj, was confirmed by FTIR. Steady-state and time-resolved fluorescence showed a strong fluorescence quenching of porphyrin in the presence of GO, indicative of a photoinduced electron transfer process from porphyrin units to GO, which acts as an electron acceptor. The surface plasmon coupling effect promoted by the AuNP@GO hybrids, proved to be effective only in the case of the noncovalent hybrid, detected through the decrease of the porphyrin fluorescence lifetime and increase in the emission intensity in solution, in good agreement with FLIM results on deposited samples.info:eu-repo/semantics/publishedVersio

Evaluation of meso-substituted cationic corroles as potential antibacterial agents

ABSTRACT Cationic derivatives of 5,10,15-tris[4-(pyridin-4-ylsulphanyl)-2,3,5,6-tetrafluorophenyl]-corrolategallium(III)pyridine and 5,10,15-tris[4-(pyridin-2-ylsulfanyl)-2,3,5,6-tetrafluorophenyl]-correlategallium(III)pyridine were synthesized and their photosensitizing properties against the naturally bioluminescent Gram-negative bacterium Allivibrio fischeri were evaluated. The cationic corrole derivatives exhibited antibacterial activity at micromolar concentrations against this Gram-negative bacterium strain

Mechanistic insights on the site selectivity in successive 1,3-dipolar cycloadditions to meso-tetraarylporphyrins

A DFT study on site selectivity in successive 1,3-dipolar cycloadditions of meso-tetraarylporphyrins with azomethine ylide and N-methylnitrone has been carried out. The calculation of the thermodynamic stability of both ylide and nitrone-derived adducts reveals that bacteriochlorins are more stable and have stronger aromatic character than isobacteriochlorins. Calculations of whole reaction pathways show that cycloadditions of azomethine ylide on porphyrin and its derived chlorin are irreversible and hence kinetically controlled. Solvent influence on the site selectivity of this reaction has also been considered, and appears to be decisive in controlling the site selectivity. In contrast, cycloadditions of nitrone over porphyrin and chlorin are clearly reversible, pointing to a thermodynamic control of these reactions.This work was supported by the Ministerio de Ciencia y Tecnología (projects CTQ2005-08016 and Consolider Ingenio 2010 CSD2006-00), the University of Aveiro, the Fundação para a Ciência e a Tecnologia (grant SFRH/BPD/8374/2002 of A.M.G.S.) and FEDER for funding the Organic Chemistry Research Unit.Peer reviewe

Selective two-photon absorption in carbon dots: a piece of the photoluminescence emission puzzle

Carbon nanodots (Cdots) are now emerging as promising nonlinear fluorophores for applications in biological environments. A thorough and systematic approach to the two-photon induced emission of Cdots that could provide design guidelines to control their nonlinear emission properties is still missing. In this work, we address the nonlinear optical spectroscopy of Cdots prepared by controlled chemical cutting of graphene oxide (GO). The two-photon absorption in the 700–1000 nm region and the corresponding emission spectrum are carefully investigated. The highest two-photon absorption cross-section estimated was 130 GM at 720 nm. This value is comparable with the one reported for graphene nanoribbons with push–pull architecture. The emission spectrum depends on the excitation mode. At the same excitation energy, nonlinear excitation results in excitation-wavelength independent emission, while upon linear excitation the emission is excitation-wavelength dependent. The biphotonic interaction seems to be selective towards sp2 clusters bearing electron donor and acceptor groups found in push–pull architectures. Both linear and nonlinear emission can be understood based on the existence of isolated sp2 clusters involved in π–π stacking interactions with clusters in adjacent layers.The authors are grateful to Fundação para a Ciência e Tecnologia (FCT, Portugal), European Union, QREN, FEDER and COMPETE for funding the QOPNA, TEMA, and CQFM research unit (project Pest-C/QUI/UI0062/2013, UID/EMS/ 00481/2013 and UID/NAN/50024/2013). FCT is acknowledged for the Post-Doctoral grants of C. I. M. S., S. N. P and I. F. A. M., and for supporting the individual work contract of E. M., I. B. and P. A. A. P. M. within the Investigador FCT program (SFRH/BPD/105478/2014, SFRH/BPD/92409/2013, SFRH/BPD/ 75782/2011, IF/00759/2013, IF/00582/2015 and IF/00917/ 2013). G. G. gratefully acknowledges the funding by European Commission under individual fellowship Marie SklodowskaCurie (NANOTER, Grant Agreement 708351).Peer reviewe

Evaluation of meso-substituted cationic corroles as potential antibacterial agents

<div><p>ABSTRACT Cationic derivatives of 5,10,15-tris[4-(pyridin-4-ylsulphanyl)-2,3,5,6-tetrafluorophenyl]-corrolategallium(III)pyridine and 5,10,15-tris[4-(pyridin-2-ylsulfanyl)-2,3,5,6-tetrafluorophenyl]-correlategallium(III)pyridine were synthesized and their photosensitizing properties against the naturally bioluminescent Gram-negative bacterium Allivibrio fischeri were evaluated. The cationic corrole derivatives exhibited antibacterial activity at micromolar concentrations against this Gram-negative bacterium strain.</p></div

Characterization of Isomeric Cationic Porphyrins with β-Pyrrolic Substituents by Electrospray Mass Spectrometry: The Singular Behavior of a Potential Virus Photoinactivator

Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) have been used to differentiate the 2- and 4-methylpyridyl isomers of free-base and metallated cationic β-vinylpyridylporphyrins. The analysis by ESI-MS/MS of the deuterated analogs and semiempirical calculations of structural and electronic parameters were also undertaken. The two free-base isomers are easily differentiated by ESI-MS/MS but the presence of a metallic center renders differentiation of the metallated isomers less effective. The data acquired show that of all the studied compounds, the free-base 2-methylpyridyl isomer, which was operative in the in vitro photoinactivation of Herpes simples virus, has a different gas-phase behavior. Local distortion of the macrocycle due to the presence of the β-vinylpyridyl substituent occurs for all the compounds, but a different electron density distribution can account for the observed gas-phase behavior of this potential virus photoinactivator

New copper porphyrins as functional models of catechol oxidase

In recent years, several research groups have focused their attention on the development of synthetic and functional models of biological systems based on copper. Here we report the synthesis strategy, characterization, and catalytic activity for new copper-based porphyrins (CuP2 and CuP3) isolated by metallation of the corresponding free base derivatives, H(2)P2 and H(2)P3. The solid CuP2S was obtained from the reaction of H2P2 with copper(II) acetate (10 equiv.). These complexes have been used in homogeneous (CuP2 and CuP3) and heterogeneous (CuP2S) oxidative catalysis of 3,5-di-tent-butylcatechol and catechol, in the presence of air, with or without hydrogen peroxide. The obtained results show that the new copper porphyrins CuP2 and CuP3 and the CuP2S material are able to efficiently mimic the activity of catechol oxidase, the latter being easily reused and maintaining its activity for more than three catalytic cycles. (C) 2016 Elsevier Inc. All rights reserved