Photolysis of asym-N2O4 (ONONO2) isolated in an argon matrix at 11 K

Intermediates Involved in the Oxidation of Nitrogen Monoxide: Photochemistry of the cis‐N2O2⋅O2 complex and of sym‐N2O4 in Solid Ne Matrices

“…3) The absence of a N= 18 O absorption redshifted from the feature at 1833 cm À1 by 46 cm À1 ( Figure 5, trace c) supports the assignment of the bands at 1833, 1626 and 1280 cm À1 to 16 ONNA C H T U N G T R E N N U N G ( 16 O) 18 O, rather than to an ONONO 2 species formed by asymmetric dimerisation of N-…”

“…[37,38] The present results rule out this possibility, as this would lead to a 16/18 O randomisation in the experiment using 18 O 2 . Thus, although the present work reinforces the recently predicted overall reaction scheme for the rearrangement of the cis-N 2 O 2 ·O 2 complex, [39][40][41] modifications are necessary to allow for low-energy pathways leading from the (NO 2 ) 2 radicalpair intermediate to both the final products trans-ONONO 2 and sym-N 2 O 4 as depicted in Scheme 2.…”

“…Furthermore, the formation of four different 18 O isotopomers of trans-ONONO 2 in the experiment using labelled 18 O 2 indicates its formation via a ground-state NA C H T U N G T R E N N U N G ( 16 O) 18 O radical pair rather than its formation by a concerted ONOONO decomposition, as has been proposed recently. [40] By the same reasoning also the supposed involvement of excited NO 2 * (A 2 B 2 ) radicals, [40] formed by the decomposition of the dinitroso peroxide, in the formation of trans-ONONO 2 can be ruled out, as in these cases only two trans isotopologues with a bridging 18 O atom would have been formed. This follows from the negligible reaction barrier and the geometric constraint within the matrix cage, which does not allow for a considerable reorientation of the electronically excited NO 2 * radical.…”

“…Oxygen (99.99 %, Messer-Griesheim), 18 O 2 (99 % Campro) and neon (99.999 % Linde) were used without further purification. NA C H T U N G T R E N N U N G ( 16/18 O) 2 iso-A C H T U N G T R E N N U N G topologues were produced in a pre-cleaned 500 mL Duran glass reactor kept in the dark at ambient temperatures.…”

“…In our previous far-IR study, devoted to the NO 3 radical, [1] spectra of the full 18 O isotopologue of trans-ONONO 2 have been obtained, and the corresponding 16/18 O isotopic shifts of n 6 , n 7 and n 8 are compiled in Table 4 O 2 were shown to yield the same four isotopomers of trans-ONONO 2 (Scheme 1) by irradiation of the corresponding deposits. [1] The most intriguing features of the vibrational spectrum of trans-ONONO 2 are the striking differences between the two central NÀO single bonds.…”