Search results for "Singlet Oxygen"

Adducts of free-base meso-tetraarylporphyrins with trihaloacetic acids: Structure and photostability

2020

Abstract Four diverse meso-tetraarylporphyrins in the form of diprotonated adducts with trifluoro-, trichloro-, tribromoacetic acids and acetic acid were investigated in benzene solution. Despite similar structural distortion of the chromophore system due to protonation, the respective adducts demonstrated different photostability when exposed to UV irradiation. The trifluoro- and trichloroacetic adducts, and the acetic acid one, showed some common features both molecular and in the mechanism of photodegradation. However, the tribromo-derivative decayed according to a different kinetic scheme, revealing a considerable impact of the bromine atoms upon the pyrrole units of the porphyrin macro…

Fe3O4@Au@mSiO2 as an enhancing nanoplatform for Rose Bengal photodynamic activity

2017

A novel nanoplatform composed of three types of materials with different functionalities, specifically core-shell Fe3O4@Au nanoparticles encapsulated near the outer surface of mesoporous silica (mSiO2) nanoparticles, has been successfully synthesised and used to enhance the efficiency of a photosensitiser, namely Rose Bengal, in singlet oxygen generation. Fe3O4 is responsible for the unusual location of the Fe3O4@Au nanoparticle, while the plasmonic shell acts as an optical antenna. In addition, the mesoporous silica matrix firmly encapsulates Rose Bengal by chemical bonding inside the pores, thus guaranteeing its photostability, and in turn making the nanosystem biocompatible. Moreover, th…

Photolysis of N-hydroxpyridinethiones: a new source of hydroxyl radicals for the direct damage of cell-free and cellular DNA.

1996

N-Hydroxypyridine-2-thione (2-HPT), known to release hydroxyl radicals on irradiation with visible light, and two related compounds, viz. N-hydroxypyridine-4-thione (4-HPT) and N-hydroxyacridine-9-thione (HAT), were tested for their potency to induce DNA damage in L1210 mouse leukemia cells and in isolated DNA from bacteriophage PM2. DNA single-strand breaks and modifications sensitive to various repair endonucleases (Fpg protein, endonuclease III, exonuclease III, T4 endonuclease V) were quantified. Illumination of cell-free DNA in the presence of 2-HPT and 4-HPT gave rise to damage profiles characteristic for hydroxyl radicals, i.e. single-strand breaks and the various endonuclease-sensit…

Tuning the photophysical properties of anti-B18H22: efficient intersystem crossing between excited singlet and triplet states in new 4,4'-(HS)2-anti-…

2013

The tuning of the photophysical properties of the highly fluorescent boron hydride cluster anti-B18H22 (1), by straightforward chemical substitution to produce 4,4'-(HS)2-anti-B18H20 (2), facilitates intersystem crossing from excited singlet states to a triplet manifold. This subsequently enhances O2((1)Δg) singlet oxygen production from a quantum yield of ΦΔ ∼ 0.008 in 1 to 0.59 in 2. This paper describes the synthesis and full structural characterization of the new compound 4,4'-(HS)2-anti-B18H20 (2) and uses UV-vis spectroscopy coupled with density functional theory (DFT) and ab initio computational studies to delineate and explain its photophysical properties.

Cover Picture: Photo-Chromium: Sensitizer for Visible-Light-Induced Oxidative C−H Bond Functionalization-Electron or Energy Transfer? (ChemPhotoChem …

2017

Distinct photodynamics of κ-N and κ-C pseudoisomeric iron(ii) complexes

2021

Two closely related FeII complexes with 2,6-bis(1-ethyl-1H-1,2,3-triazol-4yl)pyridine and 2,6-bis(1,2,3-triazol-5-ylidene)pyridine ligands are presented to gain new insights into the photophysics of bis(tridentate) iron(II) complexes. The [Fe(N^N^N)2]2+ pseudoisomer sensitizes singlet oxygen through a MC state with nanosecond lifetime after MLCT excitation, while the bis(tridentate) [Fe(C^N^C)2]2+ pseudoisomer possesses a similar 3MLCT lifetime as the tris(bidentate) [Fe(C^C)2(N^N)]2+ complexes with four mesoionic carbenes. Financial support from the Deutsche Forschungsge-meinschaft [DFG, Priority Program SPP 2102] "Light-controlled reactivity of metal complexes" (BA 4467/7-1, LO 714/11-1, …

Vanadium pentoxide nanoparticles mimic vanadium haloperoxidases and thwart biofilm formation

2012

Marine biofouling—the colonization of small marine microorganisms on surfaces that are directly exposed to seawater, such as ships' hulls—is an expensive problem that is currently without an environmentally compatible solution1. Biofouling leads to increased hydrodynamic drag, which, in turn, causes increased fuel consumption and greenhouse gas emissions. Tributyltin-free antifouling coatings and paints1, 2, 3, 4 based on metal complexes or biocides have been shown to efficiently prevent marine biofouling. However, these materials can damage5 the environment through metal leaching (for example, of copper and zinc)6 and bacteria resistance7. Here, we show that vanadium pentoxide nanowires ac…

Ceria/polymer nanocontainers for high-performance encapsulation of fluorophores

2019

We report the synthesis of high-performance organic–inorganic hybrid fluorescent nanocapsules comprising a polymer shell armored with an inorganic layer and a liquid core containing a fluorophore. The polymeric capsules are synthesized by free radical miniemulsion polymerization and contain covalently bound carboxylate surface functionalities that allow for the binding of metal ions through electrostatic interaction. A cerium(IV) oxide nanoparticle layer, formed in situ at the surface of the hybrid nanocapsules, acts as oxygen scavenger and keeps external reactive molecular oxygen from entering into the capsules, eventually resulting in a reduction of the photooxidation of encapsulated fluo…

Synthesis, Electrochemistry, and Photophysics of Aza-BODIPY Porphyrin Dyes

2016

International audience; The synthesis of dyad and triad aza-BODIPY-porphyrin systems in two steps starting from an aryl-substituted aza-BODIPY chromophore is described. The properties of the resulting aza-BODIPY-porphyrin conjugates have been extensively investigated by means of electrochemistry, spectroelectrochemistry, and absorption/emission spectroscopy. Fluorescence measurements have revealed a dramatic loss of luminescence intensity, mainly due to competitive energy transfer and photoinduced electron transfer involving charge separation followed by recombination.

Synthesis, spectroscopic studies and biological evaluation of acridine derivatives: The role of aggregation on the photodynamic efficiency.

2018

Two new photoactive compounds (1 and 2) derived from the 9-amidoacridine chromophore have been synthesized and fully characterized. Their abilities to produce singlet oxygen upon irradiation have been compared. The synthesized compounds show very different self-aggregating properties since only 1 present a strong tendency to aggregate in water. Biological assays were conducted with two cell types: hepatoma cells (Hep3B) and human umbilical vein endothelial cells (HUVEC). Photodynamic therapy (PDT) studies carried out with Hep3B cells showed that non-aggregating compound 2 showed photoxicity, ascribed to the production of singlet oxygen, being aggregating compound 1 photochemically inactive.…