Isomer-Selective Threshold Photoelectron Spectra of Phenylnitrene and Its Thermal Rearrangement Products

Abstract

The photoionization of phenylnitrene was investigated by photoion mass-selected threshold photoelectron spectroscopy in the gas phase. Flash vacuum pyrolysis of phenyl azide at 480 °C produces the nitrene, which subsequently rearranges at higher temperatures affording three isomeric cyanocyclopentadienes, in contrast to low-temperature trapping experiments. Temperature control of the reactor and threshold photoelectron spectra allows for optimizing the generation of phenylnitrene or its thermal rearrangement products, as well as obtaining vibrational information for the corresponding ions. The adiabatic ionization energies (AIE) of the triplet nitrene (3A2) to the radical cation in its lowest-energy doublet (2B2) and quartet (4A1) spin states were determined to 8.29 ± 0.01 and 9.73 ± 0.01 eV, respectively. Vibrational frequencies of ring breathing modes were measured at 500 ± 80 and 484 ± 80 cm–1 for both the ­(2B2) and ­(4A1) cationic states, respectively. The AIE differ from the values previously reported; hence, we revise the doublet–quartet energy splitting of the phenylnitrene radical cation to 1.44 eV, in excellent agreement with composite methods and coupled cluster calculations, but considerably higher than the literature reference (1.1 eV).

Gas phase synthesis of the C40 nano bowl C40H10

“…The experiments were conducted at the X04DB beamline of the Swiss Light Source (SLS) at the Paul Scherrer Institute (PSI) utilizing a resistively heated silicon-carbide (SiC) chemical microreactor coupled to a molecular beam apparatus operated with a double velocity map imaging (VMI) photoelectron photoion coincidence spectrometer 41,[49][50][51][52][53][54] . This setup allows the exploration of molecular mass growth processes to aromatic molecules in situ via elementary reactions of pyrolytically generated aryl radicals.…”

Gas-Phase Synthesis of Coronene through Stepwise Directed Ring Annulation

“…The experiments were conducted at the X04DB beamline of the Swiss Light Source at the Paul Scherrer Institute utilizing a resistively heated silicon–carbide (SiC) chemical microreactor coupled to a molecular beam apparatus operated with a double velocity map imaging (VMI) photoelectron photoion coincidence spectrometer. − Four reaction systems were studied: acetylene (C 2 H 2 ) with 1-bromotriphenylene (C 18 H 11 Br), vinylacetylene (C 4 H 4 ) with 4-bromopyrene (C 16 H 9 Br), nitrosobenzene (C 6 H 5 NO) with phenanthrene (C 14 H 10 ), and acetylene (C 2 H 2 ) with 7-bromobenzo­[ ghi ]­perylene (C 22 H 11 Br). Briefly, 1-bromotriphenylene (C 18 H 11 Br), 4-bromopyrene (C 16 H 9 Br), phenanthrene (C 14 H 10 ; 98%; Sigma-Aldrich), and 7-bromobenzo­[ ghi ]­perylene (C 22 H 11 Br) were heated at 423 ± 1, 403 ± 1, 358 ± 1, and 513 ± 1 K in a high-vacuum oven located in the source chamber and were seeded in acetylene (C 2 H 2 ; ≥99.5%; PANGAS; acetone traces removed via ethanol/dry ice bath), vinylacetylene (C 4 H 4 ; 5% in helium, Applied Gas Inc.), nitrosobenzene (C 6 H 5 NO; 97%, Sigma-Aldrich; seeded at <1% in helium), and acetylene at backing pressures of 100, 100, 125, and 220 mbar, respectively.…”

Photoelectron Photoion Coincidence Spectroscopy of Biradicals

“…This motivated Mendez-Vega et al to reinvestigate the photoionization of 2, as produced by pyrolysis of phenylazide (C 6 H 5 -N 3 ), utilizing PEPICO spectroscopy. [57] They found that the ms-TPES of m/z 91 strongly depends on the reactor temperature. At 480 °C (Figure 3a) only two features (8.29 and 9.73 eV) are visible, while a third progression at 9.14 eV starts to grow in at 510 °C (Figure 3b).…”

“…Wentrup et al reported the interconversion of the nitriles to occur via a [1,5]-sigmatropic hydrogen or CN transfer reactions. [57,59] Figure 3a) shows the clean ms-TPES of 2, which is composed of transitions into the X + ( 2 B 2 ) and the a + ( 4 A 1 ) states, respectively. Adiabatic IEs of 8.29 + ( 2 B 2 ) and 9.73 eV ( 4 A 1 ) are in excellent agreement with composite method as well as with CASPT2 calculations.…”

“…While the spectrum at lower temperature shows contributions of X + ( 2 B 2 ) and a + ( 4 A 1 ) states of 2 + , the ms-TPES at 510 °C (b) shows partial rearrangement to the three cyano-cyclopentadiene isomers. Replotted from the data in ref [57]…”