Particulate emissions generated from combustion processes of hydrocarbon fuels (soot) have become a significant environmental issue with implications for both human health and climate change. However, soot particles also offer exciting possibilities in the field of carbonaceous nanomaterials which have found applications in optoelectronics, bioimaging, drug delivery, and photocatalysis. This study aims to investigate the species implicated in the initial steps of soot particle formation characterized by the transformation of gaseous precursors, like polycyclic aromatic hydrocarbons (PAHs), into soot particles in the condensed phase. While PAHs have been long known to be soot precursors, recent researches suggest that resonance-stabilized radical (RSR) aromatic compounds may play a substantial role in this process. To shed light on this process, we conducted a series of experiments in a laminar diffusion sooting flame in controlled laboratory conditions, notably by implementing the excitation-emission matrix (EEM) method to study the optical properties of soot precursors. This innovative approach provides critical insights into the involvement of various kinds of aromatic species during the early steps of soot formation. In parallel with the experimental work, theoretical calculations were carried out to determine the spectral features of PAHs, PAH dimers, and resonance-stabilized PAH radicals. These calculations support the interpretation of the fluorescence EEM and assist the identification of species at the origin of soot inception. These findings contribute to a deeper understanding of the interplay between PAHs and persistent radicals, particularly at the onset of soot formation within flames.

The influence of the composition of the functional used for density functional theory computations on one structural parameter (a dihedral angle) and a spectroscopic parameter (absorption wavelength) is assessed in this study on the basis of two molecules (flavonols). In this kind of molecules, these two parameters should be correlated according to the nature of the electronic transition involved. However, it is shown herein that by varying the proportion of true exchange and correlation while building a functional, it is possible to obtain independently a large range of values for these parameters without any relation with the underlying real values. Therefore, it is concluded that the choice of a functional after a benchmark, especially using user-defined functionals, should be carried out with great care to avoid such effects.

Two titanium-based MOFs MIL-125 and MIL-125_NH2 are synthesized and characterized using high-temperature powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), N-2 sorption, Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), and electron paramagnetic resonance (EPR). Stable up to 300 degrees C, both compounds exhibited similar specific surface areas (SSA) values (1207 and 1099 m(2) g(-1) for MIL-125 and MIL-125_NH2, respectively). EPR signals of Ti3+ are observed in both, whith MIL-125_NH2 also showing-NH2 center dot+ signatures. Both MOFs efficiently adsorbed iodine in continuous gas flow over five days, with MIL-125 trapping 1.9 g.g(-1) and MIL-125_NH2 trapping 1.6 g.g(-1). MIL-125_NH2 exhibited faster adsorption kinetics due to its smaller band gap (2.5 against 3.6 eV). In situ Raman spectroscopy conducted during iodine adsorption revealed signal evolution from "free" I-2 to "perturbed" I-2, and I-3(-). TGA and in situ Raman desorption experiments showed that-NH2 groups improved the stabilization of I-3(-) due to an electrostatic interaction with NH2 center dot+BDC radicals. The Albery model indicated longer lifetimes for iodine desorption in I-2@MIL-125_NH2, attributed to a rate-limiting step due to stronger interaction between the anionic iodine species and the-NH2 center dot+ radicals. This study underscores how MOFs with efficient charge separation and hole-stabilizer functional groups enhance iodine stability at higher temperatures.

Aryl diazonium salts are versatile compounds known for their reactivity in various transformations. In this study, we explored the arylation of 3‐methylene isoindolinones using aryl diazonium salts. The objective was to develop a method for accessing 3‐benzyl‐3‐methoxyisoindolin‐1‐ones, a class of compounds with diverse biological activities and synthetic importance. Optimization of the reaction conditions revealed the significance of light irradiation for improved yields. The substrate scope investigation demonstrated the compatibility of various diazonium salts and N‐substituents on the 3‐methylene isoindolinone scaffold, yielding the corresponding methoxy lactams with high yields. Mechanistic insights were obtained by observing the effect of base and light irradiation. Two initiation mechanisms were proposed: in the presence of a base, the reaction could proceed even without light irradiation, while light irradiation was necessary in the absence of a base. DFT calculations were performed to elucidate the mechanism of the reaction and provide energetic considerations

The photo-physical properties of dicyanoanthracene (DCA) molecules adsorbed on the external surface of ZSM-5 zeolite, forming DCA@ZSM-5 composites, have been investigated by picosecond transient emission, femtosecond transient absorption infrared vibrational spectroscopy, steady-state UV–vis, and quantum chemistry calculations. Following the photoexcitation at 420 nm of DCA@ZSM-5, the formation of the localized, LE, excited S 1 state of DCA emitting below 500 nm is observed. LE is rapidly and quasi-exclusively converted into two distinct exciplex species, EX1 and EX2, detected by their emission above 520 nm, with a lifetime of 5 ns and 20 ns, respectively. The different transient species can be identified by the frequency of the CN stretching vibration that is a marker of the charge delocalisation and that is peaking respectively at 2162 (LE), 2174 (EX1) and 2187 (EX2) cm −1 . DFT and TD-DFT calculations further support the assignment. The results show that the external surface of zeolite is an appropriate playground for the development of novel photoactive host–guest materials.

An environmentally friendly electrochemical process for the direct trifluoromethylation of 2-pyridones with a broad substrate scope has been developed.

Titanium chemistry in aqueous acidic media has been extensively investigated over the last decades. Hydrolyzed species such as Ti(OH)(3+), TiO2+, Ti(OH)(2)(2+) or Ti(OH)(3)(+) have been identified and their equilibria have been studied in nitric and perchloric acid. A predominance of the divalent cations was found for low pH (i.e., pH <2). Nonetheless, recent literature reports the existence of small titanium oxo-clusters in aqueous acidic media for large titanium(iv) concentration (typically., >0.1 mol L-1), as stable precursors for the formation of condensed titanium dioxide. The present paper reconsiders firstly previous knowledge about the speciation of titanium(iv) in non-complexing acidic media by giving evidence for the presence of polynuclear hydrolyzed species, even at very low Ti(iv) concentration (i.e., typically <0.1 mmol L-1). UV-visible absorbance spectra recorded for diluted nitric acid solutions (a model of non-complexing acidic medium) containing titanium(iv) were compared to time-dependent density functional theory (TD-DFT) predicted excitation energies. Experimental and predicted maximal absorbance wavelengths showed significantly improved matches when polynuclear species were considered in TD-DFT calculation. Then, 0.1-12.7 mol L-1 phosphoric acid solutions containing titanium(iv) were studied by means of spectroscopic techniques (UV-visible, NMR) in order to identify qualitatively the presence of titanium(iv) complexes and to link this speciation to the acid concentration. Two different titanium(iv) orthophosphate complexes, potentially polynuclear, were detected, and the presence of free titanium(iv) is also expected for low phosphoric acid concentration (i.e., <0.1 mol L-1). A general complexation scheme for a large range of H3PO4 concentration was thus formulated.

Morin (2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one) is an abundant flavonoid with various pharmacological and biological activities. Considering the ubiquitous presence of calcium cations in biological systems, it seems relevant to study the interaction of this ion with morin and the influence of pH on this system. In a first step, among the four hypothetical chelation sites, the preferential fixing site, its protonation state and the Ca environment have been determined by combining electronic spectroscopies and density functional theory (DFT) and time-dependent DFT calculations. Then, using the same methodology, the fate of the formed complex with the variation of pH was studied. Calcium chelation occurs with the 3-hydroxy-4-keto site with deprotonation of the hydroxyl group. The coordination number of CaII does not seem to be a determining parameter insofar whatever the number of solvent molecules present in the coordination sphere of the metal, the calculation of the electronic transitions leads to the same results. With the increase in pH, a first deprotonation of the complex occurs at the level of a solvent molecule in the metal coordination sphere, followed by a deprotonation of the hydroxyl function in position 7.

2',3-Dihydroxyflavone (2'3HF) is a natural flavonol that has barely ever been studied, however the scarce studies of its physico-chemical properties have highlighted its atypical behaviour. We present a structural and spectral study of 2'3HF, performed using UV-visible absorption and fluorescence spectroscopies, coupled with DFT and TD-DFT calculations. Although its structure is close to that of 3-hydroxyflavone, 2'3HF shows a much lower pK a value. We show that the origin of this particularity is the substitution by a hydroxyl group on position 2', that induces a stronger inter-ring interaction weakening the bonding of the proton at position 3. The main absorption band of the is red-shifted upon deprotonation. The remaining proton is highly bonded in between oxygen atoms 3 and 2', making the second deprotonation unattainable in methanol. The neutral form can undergo an excited-state intramolecular proton transfer to emit dual fluorescence by the normal and tautomer forms. We suggested five geometries to be the sources of the emission bands, and showed that the energy barriers to interconversions were almost null. The anion is also fluorescent. The Stokes shifts for the neutral normal and anion species are extremely high, that can be explained by the conformational rearrangement, as the species go from twisted in the ground-state, to planar in the excited-state. Finally, another emission band is evidenced when exciting in the vicinity of the absorption maximum of the anion species in acidic medium. We suggest an aggregate with the solvent to be the origin of the emission.

1,3-Butadiene is involved in a photocatalyzed amidoarylation reaction that allows the synthesis of N-allyl amides. The reaction was evaluated on a wide range of aryl diazonium salts and nitriles as co-reactants. Selectivity issues were studied from the help of a computational approach.

20,3-Dihydroxyflavone (203HF) is a natural flavonol that has barely ever been studied, however the scarce studies of its physico-chemical properties have highlighted its atypical behaviour. We present a structural and spectral study of 203HF, performed using UV-visible absorption and fluorescence spectroscopies, coupled with DFT and TD-DFT calculations. Although its structure is close to that of 3-hydroxyflavone, 203HF shows a much lower pKa value. We show that the origin of this particularity is the substitution by a hydroxyl group on position 20, that induces a stronger inter-ring interaction weakening the bonding of the proton at position 3. The main absorption band of the is red-shifted upon deprotonation. The remaining proton is highly bonded in between oxygen atoms 3 and 20, making the second deprotonation unattainable in methanol. The neutral form can undergo an excited-state intramolecular proton transfer to emit dual fluorescence by the normal and tautomer forms. We suggested five geometries to be the sources of the emission bands, and showed that the energy barriers to interconversions were almost null. The anion is also fluorescent. The Stokes shifts for the neutral normal and anion species are extremely high, that can be explained by the conformational rearrangement, as the species go from twisted in the ground-state, to planar in the excited-state. Finally, another emission band is evidenced when exciting in the vicinity of the absorption maximum of the anion species in acidic medium. We suggest an aggregate with the solvent to be the origin of the emission.