Infrared Spectroscopic Study of Perfluorobenzyl Peroxyl Radical and Its UV Photolysis Products in An Argon Matrix.

The perfluorobenzyl peroxyl radical (CFCFO) was prepared by the reaction of the perfluorobenzyl radical, generated in the gas phase by vacuum pyrolysis of the perfluorobenzyl iodide, with molecular oxygen. The IR spectra of the radicals CFCFO and CFCFO trapped in argon matrices at 10 K were measured for the first time and assigned to two conformers with the O-O moiety in anti- and gauche orientation with respect to the C-C bond by comparing the results of the matrix isolation IR spectroscopy study with the data of quantum chemical calculations at the B3LYP/aug-cc-pVTZ and CBS-QB3 levels of theory. UV photolysis of this peroxyl radical resulted in the elimination of FC═O with the formation of the perfluorophenoxyl radical CFO, which formed complexes in the matrix.

Infrared-Spectroscopic Study of (4-Methylpent-3-en-1-ynyl)methylthiocarbene, Its Photochemical Transformations, and Reactions in an Argon Matrix.

The first representative of singlet carbenes bearing both ethynyl and methylthio groups at the carbene center, (4-methylpent-3-en-1-ynyl)methylthiocarbene, has been generated in a low-temperature Ar matrix upon UV photolysis of 3,3-dimethyl-5-methylthioethynyl-3-pyrazole and detected by FTIR spectroscopy. The generation of the carbene proceeds via intermediate (3-diazo-5-methylhex-4-en-1-ynyl)methylsulfane. The comparison of FTIR spectroscopy data with the results of quantum chemical calculations (B3LYP/aug-cc-pVTZ) and NRT analysis shows that (4-methylpent-3-en-1-ynyl)methylthiocarbene has a singlet ground state with the localization of the unpaired spins on the carbon atom in the α-position to methylthio moiety.

A highly delocalized triplet carbene, 5-Methylhexa-1,2,4-triene-1,3-diyl: matrix IR identification, structure, and reactions.

The first representative of highly delocalized triplet carbenes bearing both vinyl and ethynyl groups at the formal carbene center, 5-methylhexa-1,2,4-triene-1,3-diyl, has been generated in a low-temperature Ar matrix upon UV photolysis of 5-ethynyl-3,3-dimethyl-3H-pyrazole and detected by FTIR spectroscopy. The transformation of 3H-pyrazole into the carbene proceeds in two stages via intermediate 3-diazo-5-methylhex-4-en-1-yne. According to DFT PBE/TZ2P calculations, 5-methylhexa-1,2,4-triene-1,3-diyl possesses an effective conjugation along the five-carbon chain and shows the same type of the bond length alternation as the HC(4m+1)H-type polyacetylenic carbenes.