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The reactivity of "furan-ynes" in combination with pyridine and quinoline N-oxides in the presence of a Au(I) catalyst, has been studied, enabling the synthesis of three different heterocyclic scaffolds. Selective access to two out of the three possible products, a dihydropyridinone and a furan enone, has been achieved through the fine-tuning of the reaction conditions. The reactions proceed smoothly at room temperature and open-air, and were further extended to a broad substrate scope, thus affording functionalized dihydropyridinones and pyranones.

A small library of 2,6- and 3,5-distyrenyl-substituted carborane-BODIPY dyes was efficiently synthesized by means of a Pd-catalyzed Heck coupling reaction. Styrenyl-carborane derivatives were exploited as molecular tools to insert two carborane clusters into the fluorophore core and to extend the π-conjugation of the final molecule in a single synthetic step. The synthetic approach allows to increase the molecular diversity of this class of fluorescent dyes by the synthesis of symmetric or asymmetric units with enhanced boron content. The structural characterization and the photoluminescence (PL) properties of synthesized dyes were evaluated, and the structure/properties relationships have been investigated by theoretical calculations. The developed compounds exhibit a significant bathochromic shift compared to their parent fluorophore scaffolds, and absorption and emission patterns were practically unaffected by the different substituents (Me or Ph) on the Ccluster atom (Cc) of the carborane cage or the cluster isomer (ortho- or meta-carborane). Remarkably, the presence of carborane units at 2,6-positions of the fluorophore produced a significant increase of the emission fluorescent quantum yields, which could be slightly tuned by changing the Cc-substituent and the carborane isomer, as well as introducing ethylene glycol groups at the meso-position of the BODIPY., We would like to acknowledge Dr. Emanuele Priola (UniTO) and Dr. Francesco Marra (UniTO) for technical support, and Prof. Claudio Medana (UniTO) for HRMS measurements. We acknowledge the italian MIUR, Huvepharma Italia srl, Regione Piemonte and Cassa di Risparmio di Torino for financial support. This research was funded by MINECO ((CTQ2016-75150-R) Agencia Estatal de Investigación AEI from MICINN (PID2019-106832RB-100/AEI/10.13039/501100011033) and Generalitat de Catalunya (2017 SGR1720). The work was also supported by the MICINN through the Severo Ochoa Program for Centers of Excellence FUNFUTURE (CEX2019-000917-S). Sohini Sinha was enrolled in the PhD Program of UAB. S. S. acknowledges financial support from DOC-FAM, European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 754397., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

In the plasma dry reforming, CH4 and CO2 are dissociated by electron collisions producing fragments that in turn react to form new molecules. While the production of CO, H2, and small hydrocarbons has been investigated extensively, much less is known about the plasma synthesis of oxygenated molecules, which is the target of the present work. In addition to experimental results, gas phase reactions for the production of acetic, formic and propanoic acid were investigated by DFT calculations.

The aim of this study is to improve understanding of the tropospheric oxidation of ethyne (acetylene, C2H2) and but-2-yne, which takes place in the presence of HO and O2. The details of the potential energy hypersurface have been discussed in a previous article [Maranzana et al., J. Phys. Chem. A 2008, 112, XXXX]. For both molecules, the initial addition of HO radical to the triple bond is followed by addition of O2 to form peroxyl radicals. In both reaction systems, the peroxyl radicals take two isomeric forms, E1 and E2 for ethyne and e1 and e2 for but-2-yne. Energy transfer parameters (alpha = 250 cm-1) for the ethyne system were obtained by simulating laboratory data for N2 buffer gas, where O2 was not present. In simulations of C2H2 + HO when O2 is present, E1 reacts completely and E2 reacts almost completely, before thermalization. Radical E1 produces formic acid ( approximately 44%) and E2 gives glyoxal ( approximately 53%), in quite good agreement with experiments. For but-2-yne, pressure-dependent laboratory data are too scarce to obtain energy transfer parameters directly, so simulations were carried out for a range of values: alpha = 200-900 cm-1. Excellent agreement with the available experimental yields at atmospheric pressure was obtained with alpha = 900 cm-1. Two reaction channels are responsible for acetic acid formation, but one is clearly dominant. Biacetyl is produced by reactions of e1 and, to a minor extent, e2. The peroxyl radical e2 leads to less than 8% of all products. Vinoxyl radical (which has been reported in experiments involving C2H2 + HO) and products of its reactions are predicted to be negligible under atmospheric conditions.

Alkyl peroxyls form in the atmospheric oxidation of hydrocarbons and in their combustion. When NO concentration is low, they can appreciably react with themselves. This reaction has both propagation and termination channels. Multireference second-order perturbative energy calculations CAS(16,12)-PT2/6-311G(2df,p) have been carried out on the CAS(8,8)-MCSCF/6-311G(d,p) geometries pertaining to the reaction pathways explored. The tetroxide intermediate put forward first by Russell in 1957 is found as a stable energy minimum, but the calculations indicate that, as the system moves from atmospheric to combustion temperatures, its formation becomes problematic. A concerted synchronous transition structure, apt to connect it with the termination products, formaldehyde, methanol, and dioxygen, is not found. The concerted dissociation of the two external O–O bonds in the tetroxide leads to the 3(2CH3O•)2⋯3O2 complex, with overall singlet spin multiplicity. Both termination via H transfer, to give H2CO, CH3OH, and O2, or dissociation to 2 CH3O•+O2 (possible propagation) are feasible. The former could occur in principle with production of either excited 1O2 or excited 3H2CO. However, if a sufficiently easy intersystem crossing (ISC) could take place in the complex, the process would end up with all ground-state molecules. The (possible) propagation channels are favored by higher temperatures, while lower temperatures favor the ISC mediated termination channel. A fairly good qualitative agreement with experimental T dependence of the relevant branching ratio is found. From the tetroxide over again, dissociation of a single external O–O bond leads to CH3O• and CH3O3•, or possibly to a 1(CH3O•⋯CH3O3•) complex, but further transformations along this line are not competitive.

The reactions of (1)O(2) with alkenes can share open-chain diradicals or cyclic peroxiranes as common polar intermediates. The latter in particular has been postulated on the basis of trapping experiments, which exploit the capability of reducing agents (R) to extract an oxygen atom from the putative perepoxide, to generate an epoxide. This theoretical study illustrates that trapping experiments cannot distinguish between a peroxirane and an open-chain intermediate pathway, because an epoxide is the shared outcome of the attack by R.

To assess if reactions with oxygen species can induce a mass increase of polycyclic aromatic hydrocarbons, we exposed naphthalene molecules to an oxidative gas flow containing the radicals H and HO (2Π3/2) and the diradicals O (3P) and O2 (3Σ−g). We observed the formation of 1- and 2-naphtol, 1,4-naphthoquinone, naphthalene-derived cyclic ethers, an ester from ring opening, and ether adducts containing two naphthalene units. We investigated the possible reaction pathways as a function of temperature by density functional calculations. We found that the reactivity is characterized by HO, O and H addition to naphthalene, or by H abstraction from it, with roles depending on temperature. In conclusion, oxygen species can promote, under the experimental conditions, mainly naphthalene oxidation and, to a lesser extent, substantial molecular growth, with an efficiency that the calculations indicate to depend on the system temperature. Future experiments should try to quantify key species to allow defining the relative importance of the various reaction mechanisms uncovered by ab initio calculations.

Polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanoparticles can be oxidized right from their inception and all through their growth. Oxidation can also promote their degradation. This modelistic density functional theory (DFT) study explores, in a descriptive manner, if oxidation can mediate the earliest stages of nucleation ("functionalized nucleation"), though contrasted by mass declension triggered by oxidation itself. Initial O ((3) P) attack onto pyrene, chosen as a representative of a generic small PAH or nascent soot lamella, forms an oxyl diradical intermediate that can evolve into an open-shell epoxide, phenol, or ketone species or, alternatively, undergo mass depletion from the beginning (without impeding further additions). Open-shell intermediates can add O or O2 ((3) Σg (-) ) and ethyne, in any order, and open the way, through formation of carbon and oxygen bridges, to the addition of a second molecule of pyrene, whereas formation of direct carbon-carbon links between the two PAH-like parts might also occur.

The kinetics of gas phase reactions of the ions C 5 H 5 M + (M=V, Co, Ni and Ru) with oxygen (Me 2 CO, Me 2 O, MeOH, Me 2 CHOH, H 2 O) and nitrogen (NH 3 , NH 2 Me, NHMe 2 , NMe 3 ) donor ligands have been studied by Ion Trap Mass Spectrometry. The kinetic data confirm the previously found dependence of the log of the rate constants upon the ligand ionization energy. To get some insight on the origin of the existing barrier to the reaction some experiments were performed at various temperatures; it was found that the kinetic constants increased when the temperature decreased. The results are compatible with an entropy effect on the free energy of activation as also shown by some calculations performed for the reaction of the C 5 H 5 Fe + ion with water.

The gas-phase chemistry of gaseous germane/ethene mixtures has been investigated by ab initio theoretical calculations and by experiments to examine the formation and growth of germanium-/carbon-containing species. Ion/molecule reactions in GeH4/C2H4 mixtures have been studied with an ion trap mass spectrometer. Ion abundance variations as a function of reaction time, reaction paths originating from primary ions of both reagents, and reaction rate constants of the main processes have been determined. The highest yield of new Ge−C bonds formed via reactions of Ge-containing ions with ethene molecules was obtained in mixtures carrying similar amounts of germane and ethene. Reactions of GeH2•+ with ethene play a prominent role in this system. High-level theoretical methods were therefore used to determine the geometrical structures and energies of transition structures, reaction intermediates, and final products for several reaction pathways. Formation of the adduct between GeH2•+ and H2CCH2 is the initial s...

Formation of the first ring structure from small aliphatic molecules is often regarded as the rate-determining step (and in any case as a step of paramount importance) in the combustive growth of larger aromatic systems and soot lamellae. Among possible reactions able to start off this process, the radical addition of the propargyl radical to butadiyne (diacetylene) has been recently studied theoretically [G. da Silva, A. Trevitt, Phys. Chem. Chem. Phys. 13 (2011) 8940] and shown to lead preferentially to a 5-membered ring intermediate. The same reaction is here addressed focusing instead on the possible formation of 6-membered rings. The large variety of partially intertwined reaction pathways is the basis for a subsequent RRKM study (carried out at different combustion temperatures). It confirms, on one hand, the favored formation of fulvenallenyl radical indicated by da Silva and Trevitt, but also indicates the possible formation of six-membered cyclic systems as minor products. In particular, at high pressure, six-membered ring system yields are very low, but at lower pressures a more significant yield of six-membered ring product is predicted.

The ozonization mechanism for polycyclic aromatic hydrocarbons (PAHs) and soot is investigated by quantum mechanical calculations carried out on molecular and periodic systems. PAHs, interesting per se, serve also to model the local features of the graphenic soot platelets, for which another model is provided by a periodic representation of one graphenic layer. A concerted addition leads to a primary ozonide, while a nonconcerted attack produces a trioxyl diradical (in which one of the two unpaired electrons is pi-delocalized). Easy loss of (i) (1)O(2) or (ii) (3)O(2) from either intermediate, with spin conservation, would yield stable (i) singlet or (ii) triplet pi-delocalized species which carry an epoxide group. The trioxyl diradical pathway is estimated to be preferred, in these systems. An intersystem crossing, taking place in the trioxyl diradicals, can be invoked to allow the even easier loss of a ground-state oxygen molecule with the formation of a ground-state epoxide in a more exoergic and less demanding step. We propose that soot ozonization can take place by such a process, with ultimate functionalization of the graphenic platelets by epoxide groups.

The reactivity of biphenylium cations C12H9(+) with benzene C6H6 is investigated in a joint experimental and theoretical approach. Experiments are performed by using a triple quadruple mass spectrometer equipped with an atmospheric pressure chemical ion source to generate C12H9(+) via dissociative ionization of various isomers of the neutral precursor hydroxybiphenyl (C12H10O). C-C coupling reactions leading to hydrocarbon growth are observed. The most abundant ionic products are C18H15(+), C18H13(+), C17H12(+), and C8H7(+). The dependence of product ion yields on the kinetic energy of reagent ions, as well as further experiments performed using partial isotopic labelling of reagents, support the idea that the reaction proceeds via a long lived association product, presumably the covalently bound protonated terphenyl C18H15(+). Its formation is found to be exothermic and barrierless and, therefore, might occur under the low pressure and temperature conditions typical of planetary atmospheres and the interstellar medium. Theoretical calculations have focussed on the channel leading to C8H7(+) plus C10H8, identifying, as the most probable fragments, the phenylethen-1-ylium cation and naphthalene, thus suggesting that the pathway leading to them might be of particular interest for the synthesis of polycyclic aromatic hydrocarbons. Both experiments and theory agree in finding this channel exoergic but hampered by small barriers of 2.7 and 3.7 kcal mol(-1) on the singlet potential energy surface.