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Dalton Trans ; 47(32): 11123-11135, 2018 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-30043792


A new Zn(ii) porphyrin-based dendrimer (52) containing twelve Ru(ii) alkynyl fragments, has been prepared following a convergent approach in two steps from 5,10,15,20-tetra(4-ethynylphenyl)porphyrinatozinc(ii) (6). The cubic nonlinear optical (NLO) properties of 52 and other derivatives of 6 have been measured by third-harmonic generation (THG) at 1907 nm and by Z-scan over the spectral range 500-1700 nm, revealing the remarkable NLO response of 52 in the near-IR range. These results highlight the beneficial role of the extended "cross fourchée"-like polymetallic structure of 52 on its third-order NLO properties.

Chemosphere ; 208: 352-357, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29885500


The present study aims to quantify acrylamide in caffeinated beverages including American coffee, Lebanese coffee, espresso, instant coffee and hot chocolate, and to determine their carcinogenic and neurotoxic risks. A survey was carried for this purpose whereby 78% of the Lebanese population was found to consume at least one type of caffeinated beverages. Gas Chromatography Mass Spectrometry analysis revealed that the average acrylamide level in caffeinated beverages is 29,176 µg/kg sample. The daily consumption of acrylamide from Lebanese coffee (10.9 µg/kg-bw/day), hot chocolate (1.2 µg/kg-bw/day) and Espresso (7.4 µg/kg-bw/day) was found to be higher than the risk intake for carcinogenicity and neurotoxicity as set by World Health Organization (WHO; 0.3-2 µg/kg-bw/day) at both the mean (average consumers) and high (high consumers) dietary exposures. On the other hand, American coffee (0.37 µg/kg-bw/day) was shown to pose no carcinogenic or neurotoxic risks among the Lebanese community for consumers with a mean dietary exposure. The study shows alarming results that call for regulating the caffeinated product industry by setting legislations and standard protocols for product preparation in order to limit the acrylamide content and protect consumers. In order to avoid carcinogenic and neurotoxic risks, we propose that WHO/FAO set acrylamide levels in caffeinated beverages to 7000 µg acrylamide/kg sample, a value which is 4-folds lower than the average acrylamide levels of 29,176 µg/kg sample found in caffeinated beverages sold in the Lebanese market. Alternatively, consumers of caffeinated products, especially Lebanese coffee and espresso, would have to lower their daily consumption to 0.3-0.4 cups/day.

Acrilamida/toxicidade , Bebidas/análise , Cafeína/química , Carcinógenos/toxicidade , Exposição Dietética/efeitos adversos , Contaminação de Alimentos/análise , Síndromes Neurotóxicas/epidemiologia , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Feminino , Humanos , Líbano/epidemiologia , Masculino , Pessoa de Meia-Idade , Síndromes Neurotóxicas/etiologia , Medição de Risco , Adulto Jovem
Inorg Chem ; 54(13): 6347-55, 2015 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-26068041


With the help of EPR spectroscopy, we show that the diamagnetic [Ru(dppe)2(-C≡C-R)2] system sets up a magnetic coupling between two organic radicals R, i.e., two nitronyl nitroxide or two verdazyl units, which is stronger than that of related platinum organometallic systems. Surprisingly, further oxidation of the ruthenium redox-active metal coupling unit (MCU), which introduces an additional spin unit on the carbon-rich part, leads to the switching off of this interaction. On the contrary, in simpler complexes bearing only one of the organic radical ligands [C6H5-C≡C-Ru(dppe)2-C≡C-R], one-electron oxidation of the transition metal unit generates an interaction between the two spin carriers of comparable magnitude to that observed in the above corresponding neutral systems.

Dalton Trans ; 44(17): 7748-51, 2015 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-25854620


A new Zn(ii) porphyrin-cored ruthenium alkynyl dendrimer (2) containing twelve Ru(κ(2)-dppe)2 bis-alkynyl fragments has been prepared in two steps from 5,10,15,20-tetra(4-ethynylphenyl)porphyrinatozinc(ii) and shown to be highly active for third-harmonic generation (THG) at 1907 nm.

Dalton Trans ; 44(20): 9470-85, 2015 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-25915654


Reactions of the 16-electron ruthenium complex [Ru(dppe)2Cl][PF6] with metal-free and zinc ethynylphenyltrifluorenylporphyrins and respectively, gave the new dyads and with ethynylruthenium group as a potential electron donor and the porphyrin as a potential electron acceptor. The redox properties of the porphyrins were investigated by cyclic voltammetry and UV spectroelectrochemistry (SEC), which reveal that the monocation and monoanion of metal-free porphyrin are stable under these conditions whereas the formation of the corresponding radical cation or anion of the zinc porphyrin was accompanied by partial decomplexation of the zinc ion. Oxidations of the dyads and gave stable radical cations as probed using IR, NIR and UV SEC methods. These cations show similar NIR and IR bands to those reported for the known 17-electron [Ru(dppe)2(C[triple bond, length as m-dash]CPh)Cl](+) radical cation. Remarkably, the dyad has four stable redox states +2/+1/0/-1 where the second oxidation and first reduction processes take place at the porphyrin unit. Simulated absorption spectra on at optimised geometries obtained by TD-DFT computations with the CAM-B3LYP functional are shown to be in very good agreement with the observed UV absorption spectra of . The spectra of and their oxidised and reduced species were interpreted with the aid of the TD-DFT data. Fluorescence measurements reveal that the dyads and are only weakly emitting compared to and , indicative of quenching of the porphyrinic singlet excited state by the ruthenium centre.