ESR spectra of fluorine-containing radicals of phosphorus and arsenic

ESR spectra observed at 120 K in γ-irradiated solid solutions of PF_5 in neopentane and AsF_5 in SF_6 are ascribed to the radical ions PF_5^− and AsF_5^− in which the unpaired electron interacts strongly with the central nucleus and with four equivalent ^(19)F nuclei. Hyperfine interaction with the fifth ^(19)F nucleus was not resolvable in either case. The spectra were quite distinct from those of the tetrafluorides PF_4 and AsF_4, thus eliminating the possibility that they were due to tetrafluoride radicals undergoing rapid intramolecular ^(19)F exchange

Gold potential of the Dalradian rocks of north-west Northern Ireland : prospectivity analysis using Tellus data

The Dalradian terrane in the north-west of Northern Ireland is prospective for orogenic vein-hosted gold mineralisation with important deposits at Curraghinalt and Cavanacaw. New geochemical and geophysical data from the DETI-funded Tellus project have been used, in conjunction with other spatial geoscience datasets, to map the distribution of prospectivity for this style of mineralisation over this terrane. A knowledge-based fuzzy logic modelling methodology using Arc Spatial Data Modeller was utilised. Four main groups of targets were identified, many close to known occurrences in the Lack - Curraghinalt zone and others in prospective areas identified by previous investigations. Additional targets are located along west-north-west trending linear zones at the eastern end of the Newtownstewart Basin and to the north of the Omagh-Kesh Basin. These zones may be related to major structures linked to a westward extension of the Curraghinalt lateral ramp which is regarded as an important control on the location of the Curraghinalt deposit

2-pyridyinitrene from tetrazolo[1,5-a]pyridine and Pyrido[2,3-a][1,2,4]oxadiazol-2-one

Flash vacuum thermolyses of tetrazolo[1,5-a]pyridine and pyrido[2,3-a][1,2,4]oxadiazol-2-one generate 2-pyridylnitrene, which was detected by Ar matrix ESR spectroscopy. The thermolysis products are 2-aminopyridine, Z- and E-glutacononitriles, and 2- and 3-cyanopyrroles. The products are formed in the same ratios from the two precursors

2-pyridylnitrene and 3-pyridazylcarbene and their relationship via ring-expansion, ring-opening, ring-contraction, and fragmentation

Photolysis of triazolo[1,5-b]pyridazine 8 isolated in Ar matrix generates diazomethylpyridazines 9Z and 9E and diazopentenynes 11Z and 11E as detected by IR spectroscopy. ESR spectroscopy detected the 3-pydidazylcarbene 10 as well as pent-2-en-3-yn-1-ylidene 12 formed by loss of one and two molecules of N(2), respectively. Further photolysis caused rearrangement of the carbenes to 1,2-pentadien-4-yne 13 and 3-ethynylcyclopropene 14. Flash vacuum thermolysis (FVT) of 8 at 400-500 degrees C with Ar matrix isolation of the products yielded 13, 14, and 1,4-pentadiyne 15. At higher temperatures, glutacononitriles 27Z and 27E were formed as well together with minor amounts of 2- and 3-cyanopyrroles 28 and 29. Tetrazolo[1,5-a]pyridine/2-azidopyridine 22T/22A yields 2-pyridylnitrene 19 as well as the novel open-chain cyanodienylnitrene 23 and the ring-expanded 1,3-diazacyclohepta-1,2,4,6-tetraene 21 on short wavelength photolysis. Nitrenes 19 and 23 were detected by ESR spectroscopy, and cumulene 21 by IR and UV spectroscopy. FVT of 22T/22A also affords 2-pyridylnitrene 19 and diazacycloheptatetraene 21, as well as glutacononitriles 27Z,E and 2- and 3-cyanopyrroles 28 and 29. Photolysis of 21 above 300 nm yields the novel spiroazirene 25, identified by its matrix IR spectrum. The reaction pathways connecting the four carbenes (10Z,E and 12Z,E) and three nitrenes (19, 23EZ, and 23ZZ) in their open-shell singlet and triplet states are elucidated with the aid of theoretical caculations at DFT, CASSCF, and CASPT2 levels. Three possible mechanisms of ring-contraction in arylnitrenes are identified: (i) via ring-opening to dienylnitrenes, (ii) concerted ring-contraction, and (iii) via spiroazirenes 25, whereby (i) is the energetically most favorable