Among all existing complex organic molecules, glycolaldehyde HOCH 2 CHO and ethylene glycol HOCH 2 CH 2 OH are two of the largest detected molecules in the interstellar medium. We investigate both experimentally and theoretically the low-temperature reaction pathways leading to glycolaldehyde and ethylene glycol in interstellar grains. Using infrared spectroscopy, mass spectroscopy and quantum calculations, we investigate formation pathways of glycolaldehyde and ethylene glycol based on HCO and CH 2 OH radical-radical recombinations. We also show that CH 2 OH is the main intermediate radical species in the H 2 CO to CH 3 OH hydrogenation processes. We then discuss astrophysical implications of the chemical pathway we propose on the observed gas-phase ethylene glycol and glycolaldehyde.

We present a new and simple scheme that aims to decompose into its main physical contributions the magnetic exchange interaction between two unpaired electrons. It is based on the popular broken-symmetry density functional theory (DFT) approach and relies on the frozen orbital capabilities of the local self-consistent field method. Accordingly, the magnetic exchange interaction energy can be separated into three main contributions: the direct exchange between magnetic orbitals, the spin polarization of the core orbitals, and the relaxation of the magnetic orbitals (kinetic exchange). This decomposition scheme is applied to a series of binuclear inorganic magnetic compounds both ferromagnetic and antiferromagnetic. The direct exchange is determined from the restricted DFT description. On the one hand, starting from the restricted orbital set and relaxing only the magnetic orbitals provides the kinetic exchange contribution and an estimate of the t and U parameters of the generalized Anderson mechanism. On the other hand, relaxing the core orbitals only introduces the spin polarization contribution. The decomposition leads to almost additive contributions. The effect of the amount of Hartree-Fock exchange on the different contributions is analyzed.

We report a molecular design and concept using π‐system elongation and steric effects from helicenes surrounding a triphenylene core toward stable chiral polycyclic aromatic hydrocarbons (PAHs) with a maximal π‐distortion to tackle their aromaticity, supramolecular and molecular properties. The selective syntheses, and the structural, conformational and chiroptical properties of two diastereomeric large multi‐helicenes of formula C90H48 having a triphenylene core and embedding three [5]helicene units on their inner edges and three [7]helicene units at their periphery are reported based on diastereoselective and, when applicable, enantiospecific Yamamoto‐type cyclotrimerizations of racemic or enantiopure 9,10‐dibromo[7]helicene. Both molecules have an extremely distorted triphenylene core, and one of them exhibits the largest torsion angle recorded so far for a benzene ring (twist=36.9°).

Interactions of gold(I) catalysts with alkenes and alkynes are analyzed. Neutral chlorido, and cationic phosphine and N-heterocyclic carbene complexes are studied. High-level ab initio calculations are performed to benchmark the accuracy of popular DFT methods. Donation and backdonation contributions in the bond between the gold fragment and the alkene/alkyne substrate are discussed. These contributions depend on the nature of the gold fragment, but also on the substituents on the alkene/alkyne.

A new approach to extract the coefficients and weights of Lewis structures from the Hückel wave function is designed: Hückel-Lewis projection (HL-P). The weights are obtained by projection on overlapping Lewis structures. This straightforward alternative to ab initio approaches is detailed and used on typical cases, including acrolein, allyl radical, pyrrole-like systems, and imidazolylidene. A trust parameter is defined and shown as a guide to retrieve the most important Lewis structures. The emblematic examples of butadiene and benzene are chosen to illustrate the use of this parameter.

We present new laboratory experiments on the low-temperature formation of COMs such as polyoxymethylene (POM), glycolaldehyde (GA), ethylene glycol (EG) and possibly glyceraldehyde (GCA) and glycerol (GCO) through radical-induced reactivity from VUV photolysis of formaldehyde in Ar and Xe matrices. The radical reactivity and the endogenous formation of COMs were monitored in-situ via infrared spectroscopy in the solid state and post photolysis with temperature programmed desorption (TPD) using a quadripole mass spectrometer. Based on experimental finding and quantum calculations, we elaborate a formation pathway for formaldehyde polymerisation induced by radicals (HCO and CH 2 OH) that support the POM formation in cometary environments. In addition, fragmentation patterns obtained from the sublimation of short chain-length POM are consistent with data collected by the Ptolemy instrument on-board the Rosetta mission and strengthen the POM identification made by this instrument.

Ab initio calculations on the metal (groups 1 and 11) cyanide complexes show two stable configurations for the ground state geometry, a linear cyanide (MCN) and a triangular (MNC) form with an obtuse M-N-C angle. Lithium complex may exist in a linear isocyanide (MNC) form, but it cannot be differentiated from the triangular configuration because of the flatness of the potential energy surface connecting the two isomers. The metal atom and cyano radical are bonded through a strongly ionic configuration (M+CN-) in both geometrical forms. The MNC triangular form is a very floppy structure having one low frequency for the bending mode, whereas the MCN linear form is more rigid. The CN complexes of the alkali atoms have a triangular geometry as the lowest energy conformer, while the noble metal atoms prefer the linear cyanide one. The relative stability of the two isomers, dipole moments, and effective charges are reported in this paper. The essential aspects of the potential energy surfaces for the ground and the first excited states exhibiting a closely avoided crossing are also explained.

Electron delocalization in contorted polycyclic aromatic hydrocarbon (PAH) molecules was examined through 3D isotropic magnetic shielding (IMS) contour maps built around the molecules using pseudo-van der Waals surfaces. The resulting...