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Polycyclic aromatic hydrocarbons (PAHs) are the most widespread xenobiotic pollutants in water and their abatement usually involves expensive and energy-consuming treatments. In this work, anthracene (AN) was selected as the recalcitrant model of PAHs and its solar light-stimulated heterogeneous photocatalytic abatement in aerated aqueous media was investigated using a new TiO derived thermoplastic nanocomposite in thin film form. The results were also compared with the benchmark TiO photocatalyst in slurry form. Finally, the possible contribution of reactive intermediates such as hydroxyl radical, AN radical cation and singlet oxygen, was investigated by using a hydroxyl radical trap and laser flash photolysis. Based on the obtained results, a feasible mechanism for AN photodegradation, which involves hydroxyl radical as the key oxidizing species is proposed., This research was funded by the University of Catania (Piano di incentivi per la ricerca di Ateneo, PIACERI–Linea 2).

Photosensitized thymine<>thymine (Thy<>Thy) formation and repair can be mediated by carbazole (Cbz). The former occurs from the Cbz triplet excited state via energy transfer, while the latter takes place from the singlet excited state via electron transfer. Here, fundamental insight is provided into the role of the topology and excited state multiplicity, as factors governing the balance between both processes. This has been achieved upon designing and synthesizing different isomers of trifunctional systems containing one Cbz and two Thy units covalently linked to the rigid skeleton of the natural deoxycholic acid. The results shown here prove that the Cbz photosensitized dimerization is not counterbalanced by repair when the latter, instead of operating through-space, has to proceed through-bond., Financial support from the Spanish Government (grant SEV-2016-0683), Generalitat Valenciana (PROMETEO/2017/075 and PROMETEO/2021/077), and Technical University of Valencia (Predoctoral FPI fellowship for P.M.) is gratefully acknowledged. G.S. thanks CTI-CSIC for the use of computational facilities.

Luminol is a prominent chemiluminescent (CL) agent, finding applications across numerous fields, including forensics, immunoassays, and imaging. Different substitution patterns on the aromatic ring can enhance or decrease its CL efficiency. We herein report a systematic study on the synthesis and photophysics of all possible 6,8-disubstituted luminol derivatives bearing H, Ph, and/or Me substituents. Their CL responses are monitored at three pH values (8, 10, and 12), thus revealing the architecture with the optimum CL efficiency. The most efficient pattern is used for the synthesis of a strongly CL luminol derivative, bearing a functional group for further, straightforward derivatization. This adduct exhibits an unprecedented increase in chemiluminescence efficiency at pH = 12, pH = 10, and especially at pH = 8 (closer to the biologically relevant conditions) compared to luminol. Complementary work on the fluorescence of the emissive species as well as quantum chemistry computations are employed for the rationalization of the observed results., The authors would like to thank Ekaterini Bouga and Christina-Ioanna Vrettou for assisting with certain synthesis steps. This project was financially supported by the European Union’s Horizon 2020 framework program for research and innovation under Grant Agreement No. 712921. T.M. and A.P. would like to thank the State Scholarships Foundation (IKY) for financial support via Ph.D. fellowships through the “Strengthening of Human Resources through Doctoral Research” program of the Operational Program “Human Resource Development, Education and Lifelong Learning” 2014–2020, co-financed by the European Union (European Social Fund ESF) and Greek national funds. The authors would also like to thank Prof. N. Thomaidis and Dr. Maria-Christina for the HRMS analyses. M.A.M. and G.M.R.-M. thank the Generalitat Valenciana (Prometeo Program/2017/075) for financial support. A.G. and D.R.-S. acknowledge Spanish “Ministerio de Ciencia e Innovación (MICINN)” (Project Ref CTQ2017-87054-C2-2-P). A.G. is also thankful to the MICINN for a “Juan de la Cierva” grant (Ref IJC2018-035123-I). D.R.-S. is also thankful to the MICINN for a “Ramón y Cajal” grant (Ref RYC-2015-19234) and to the BBVA Foundation for a 2019 Leonardo Grant for Researchers and Cultural Creators.

Luminol is a prominent chemiluminescent (CL) agent, finding applications across numerous fields, including forensics, immunoassays, and imaging. Different substitution patterns on the aromatic ring can enhance or decrease its CL efficiency. We herein report a systematic study on the synthesis and photophysics of all possible 6,8-disubstituted luminol derivatives bearing H, Ph, and/or Me substituents. Their CL responses are monitored at three pH values (8, 10, and 12), thus revealing the architecture with the optimum CL efficiency. The most efficient pattern is used for the synthesis of a strongly CL luminol derivative, bearing a functional group for further, straightforward derivatization. This adduct exhibits an unprecedented increase in chemiluminescence efficiency at pH=12, pH=10, and especially at pH=8 (closer to the biologically-relevant conditions), compared to luminol. Complementary work on the fluorescence of the emissive species, as well as quantum chemistry computations are employed for the rationalization of the observed results.

[EN] A photoactive bathymeter based on a carboxylic acid moiety covalently linked to a signalling methoxynaphthalene (MNP) fluorophore has been designed to prove the concept of "snorkelling" vs. "diving" in mixed micelles (MM). The carboxylic acid "floats" on the MM surface, while the MNP unit sinks deep in MM. The rate constants of MNP fluorescence quenching by iodide, which remains basically in water, consistently decrease with increasing spacer length, revealing different regions. This is associated with the distance MNP should "dive" in MM to achieve protection from aqueous reactants. Unequivocal proof of the exergonic photoinduced electron transfer was obtained from the UV-visible spectral signature of I-3(-) upon steady-state photolysis. The applicability of the bathymeter was examined upon testing a family of MNP derivatives. The obtained results were validated by comparison with different lipophilicity tests: (i) a modified version of the K-ow partition coefficient and (ii) the retention factor on thin layer chromatography. This concept could potentially be extended to test drugs or pharmacophores exhibiting any photoactive moiety., Financial support from the Spanish Government (SEV-2016-0683), Red RETICS de Investigacion de Reacciones Adversas a Alergenos y Farmacos (RIRAAF), Instituto de Salud Carlos III (RD012/0013, RD16/0006/0030, FIS PI16/01877), VLC-Campus and the Generalitat Valenciana (Prometeo Program) is gratefully acknowledged.

Reactive oxygen species (ROS) can provoke damage to cells, where their concentrations are regulated by antioxidants. As the hydroxyl radical (&bull, OH) is the most oxidizing ROS, we have focused our attention on the use of a mechanistically based time-resolved methodology, such as laser flash photolysis, to determine the relative reactivity of alcoholic beverages towards &bull, OH as an indicator of their antioxidant potential. The selected drinks were of two different origins: (i) those derived from grapes such as red wine, white wine, white vermouth, marc and brandy and (ii) spirits not derived from grapes: triple sec, gin, whisky, and rum. Initially, we determined the quenching rate constant of ethanol with &bull, OH and then we explored the reactivity of the different beverages, which was higher than expected based on their alcoholic content. This can be attributed to the presence of antioxidants and was especially remarkable for the grape-derived drinks.

The chemical fate of radical intermediates is relevant to understand the biological effects of radiation and to explain formation of DNA lesions. A direct approach to selectively generate the putative reactive intermediates is based on the irradiation of photolabile precursors. But, to date, radical formation and reactivity have only been studied in aqueous media, which do not completely mimic the micro environment provided by the DNA structure and its complexes with proteins. Thus, it is also important to evaluate the photogeneration of nucleoside-based radicals in nonaqueous media. The attention here is focused on the independent generation of 5,6-dihydropyrimidin-5-yl radicals in organic solvent through the synthesis of new lipophilic tert-butyl ketone precursors. Formation of 5,6-dihydro-2'-deoxyuridin-S-yl and 5,6-dihydrothymidin-5-yl radicals has first been confirmed by using a new nitroxide-derived profluorescent radical trap. Further evidence has been obtained by nanosecond laser flash photolysis through detection of long-lived transients. Finally, the experimental data are corroborated by multiconfigurational ab initio CASPT2//CASSCF methodology., Spanish Government (CTQ2012-32621, CTQ2015-70164-P, CTQ2014-58624-P, RIRAAF RETICS RD12/0013/0009, Severo Ochoa program/SEV-2012-0267, Maria de Maetzu program/MDM-2015-0538, BES-2011-048326 and BES-2013-066566, JCI-2012-13431) and Generalitat Valenciana (Prometeo 11/2013/005 and GV2015-057) are gratefully acknowledged. Dr. M. Luisa Marin is also acknowledged for her help during laser flash photolysis experiments.

[EN] Based on our previous investigations into the photophysical properties of the 5-methyl-2-pyrimidone (Pyo) chromophore, we now extend our studies to the photobehavior of the dimeric (6-4) thymine photoproducts (6-4 PP) to evaluate their capability to act as instrinsic DNA photosensitizers. The lesion presents significant absorption in the UVB/UVA region, weak fluorescence emission, a singlet-excited-state energy of approximately 351 kJ mol(-1), and a triplet-excited-state energy of 297 kJ mol(-1). Its triplet transient absorption has a maximum at 420-440 nm, a lifetime of around 7 mu s, and a high formation quantum yield, Phi(ISC) = 0.86. This species is efficiently quenched by thymidine. Its DNA photosensitizing properties are demonstrated by a series of experiments run on a pBR322 plasmid. The lesion photoinduces both single-strand breaks and the formation of cyclobutane thymine dimers. Altogether, these results show that, the substitution of the pyrimidone ring at C4 by a 5-hydroxy-5,6-dihydrothymine does not cancel out the photosensitization properties of the chromophore., Spanish Government (CTQ2015-70164-P, RIRAAF RETICS RD12/0013/0009, Prometeo II program, Severo Ochoa program/SEV-2012-0267 and JAE-Predoc 2011-00740 to V. V.-C.) is gratefully acknowledged.

[EN] Azetidines are interesting compounds in medicine and chemistry as bioactive scaffolds and synthetic intermediates. However, photochemical processes involved in the generation and fate of azetidine-derived radical ions have scarcely been reported. In this context, the photoreduction of this four-membered heterocycle might be relevant in connection with the DNA (6-4) photoproduct obtained from photolyase. Herein, a stable azabipyrimidinic azetidine (AZT(m)), obtained from cycloaddition between thymine and 6-azauracil units, is considered to be an interesting model of the proposed azetidine-like intermediate. Hence, its photoreduction and photo-oxidation are thoroughly investigated through a multifaceted approach, including spectroscopic, analytical, and electrochemical studies, complemented by CASPT2 and DFT calculations. Both injection and removal of an electron result in the formation of radical ions, which evolve towards repaired thymine and azauracil units. Whereas photoreduction energetics are similar to those of the cyclobutane thymine dimers, photo-oxidation is clearly more favorable in the azetidine. Ring opening occurs with relatively low activation barriers (< 13 kcal mol(-1)) and the process is clearly exergonic for photoreduction. In general, a good correlation has been observed between the experimental results and theoretical calculations, which has allowed a synergic understanding of the phenomenon., The Spanish Government (CTQ2015-70164-P, CTQ2017-87054-C2-2-P, SVP-2013-068057 grants to A.B.F.-R. and RYC-2015-19234 grant to D.R.-S.) and the Valencia Regional Government (Prometeo/2017/075) are acknowledged for financial support. A.F.-M. is grateful to the Region Grand Est government (France) and the Universite de Lorraine for their financial support.

Electron transfer involving nucleic acids and their derivatives is an important field in bioorganic chemistry, specifically in connection with its role in the photo-driven DNA damage and repair. Four-membered ring heterocyclic oxetanes and azetidines have been claimed to be the intermediates involved in the repair of DNA (6-4) photoproduct by photolyase. In this context, we examine here the redox properties of the two azetidine isomers obtained from photocycloaddition between 6-aza-1,3-dimethyluracil and cyclohexene. Steady-state and time-resolved fluorescence experiments using a series of photoreductants and photooxidants have been run to evaluate the efficiency of the electron transfer process. Analysis of the obtained quenching kinetics shows that the azetidine compounds can act as electron donors. Additionally, it appears that the cis isomer is more easily oxidized than its trans counterpart. This result is in agreement with electrochemical studies performed on both azetidine derivatives., Spanish Government (CTQ2015-70164-P, RIRAAF RETICS RD12/0013/0009, Red de Fotoquímica Biológica CTQ2015-71896-REDT, Severo Ochoa program/SEV-2012-0267 and SVP-2013-068057 for A. B. F.-R. grant) and Generalitat Valenciana (Prometeo II/2013/005) are gratefully acknowledge. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).

[EN] Biphenyl derivative N-allyl-N'-(4'-nitro[1,1'-biphenyl]-4-yl)thiourea (BP1) was synthesized as a functional fluorescent sensor for protons and their photophysical properties were studied. The influence of environment protonation on photophysical properties of the biphenyls in solutions was investigated using UV absorption, steady-state and time-resolved fluorescence spectroscopy. Semiempirical and DFT calculations and optimization of the molecular structure of the biphenyl derivatives in vacuum, in polar solvents and in a proton-rich environment were conducted using the HyperChem, Amsol and Gaussian3 software package. Fluorescence quenching with addition of acidic acid was observed and the Stern-Volmer quenching rate constant was about 3.0 x 10(9) M-1 s(-1). Intermolecular hydrogen bonds formations by the protons with the sulphur being substituted to the biphenyls generate charge movement and strong increase (x 5) of the dipole moment of the fluorophore. (C) 2010 Elsevier B.V. All rights reserved., MS acknowledges the Polish Government for Ph.D. Grant no. 3 T08A08430. GMRM acknowledges the Spanish Government for a Ph.D. grant.

Five heteroditopic ligands have been prepared to be used in solid–liquid extraction of ω-amino acids into DMSO solutions. The prepared ligands contain crown ethers as cation binding sites and thiourea or amide groups for anion recognition. The aliphatic zone of the 1H NMR spectra suggests that two different species related to the amino acid are present in solution. One of these species is the complexed zwitterionic form and the other seems to be free non-zwitterionic amino acid. The presence of these two species allows extraction efficiencies higher than 100%.

Thioureas are able to act as organocatalysts in the electrochemical reduction of aromatic carboxylates.

Four new homoditopic biphenyl thiourea derivatives have been prepared to be used in carboxylate sensing. Experiments carried out with these ligands have demonstrated that the conformation of the free ligand has a strong influence on both complex stoichiometry and geometry. High equilibrium constants were obtained in DMSO.

Six new biphenyl thiourea derivatives have been prepared to be used in carboxylate sensing. Experiments carried out with these ligands have demonstrated that the type of interaction with TBA carboxylates is strongly dependent on the substituents in the thiourea moiety. These interactions go from the formation of 1:1 hydrogen-bonded complexes to acid–base reactions. In addition, different geometries have been observed for the complexes being dependent on the conformations of the free ligands in solution.

In this work, a kinetic model, in combination with time-resolved experiments, is applied to assess the involvement of OH in the photodegradation of emerging pollutants (EPs) by means of advanced oxidation processes. In contrast with the general assumption, quenching of the short-lived OH in the real waters by the (highly diluted) EPs must be very inefficient, so removal of EPs cannot purely rely on the generation and reaction of OH. This suggests that more complex pathways have to be considered to explain the photodegradation of EPs actually achieved under the employed oxidative conditions, possibly involving other reactive species with longer lifetimes or chain degradation processes., This work was supported by the Spanish Government (Projects CTQ2012-38754-C03-03 and CTQ2012-38754-C03-02) and Technical University of Valencia (Predoctoral fellowship for J. Gomis).

Photolysis of the benzophenone chromophore by means of high energy laser pulses has been used as a tool to populate upper thymine-like triplet states via intramolecular sensitization. These species undergo characteristic n pi* photoreactivity, as revealed by the Norrish-Yang photocyclization of 5-tert-butyluracil., Financial support by the Spanish government (CTQ2009-13699, CTQ2012-32621, RyC-2007-00476 to V.L.-V. and JAE-Predoc 2011-00740 contract to V.V.-C.) and the Generalitat Valenciana (Prometeo program) is gratefully acknowledged. M.Y, is thankful for Grants-in-Aid for Scientific Research (KAKENHI) from JSPS (No. 23350059) and the "Element Innovation" Project by the Ministry of Education, Culture, Sports, Science, and Technology, Japan.

DNA damage: The reactivity of HO. with silylated 2¿-deoxyribonucleosides was investigated in acetonitrile by means of a time-resolved technique. The obtained rate constants were in general slightly lower than those reported for the natural nucleosides in water. Analysis of the reaction mixture by UPLC-MS revealed that HO. attack occurred at the nucleobase (see scheme)., The Spanish Government (CTQ2009-13699 and Ramon y Cajal contract (RyC-2007-00476) to V. L. V) is gratefully acknowledged.