Peppe, S.Dua, S.Bowie, J.2007-02-252007-02-252001Journal of Physical Chemistry A, 2001; 105(44):10139-101451089-56391520-5215http://hdl.handle.net/2440/4624Copyright © 2001 American Chemical SocietyThe covalently bound radical anion [O<inf>2</inf>C-CO]^-. is formed when 1,3-dioxolane-2,5-dione captures an electron followed by retro-cleavage of CH<inf>2</inf>O. Calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory indicate that there are a number of neutral isomers with formula C<inf>2</inf>O<inf>3</inf>, viz. van der Waals complex O<inf>2</inf>C- - -CO (rel. energy = 0 kcal mol^-1), singlet oxiran dione (760.9 kcal mol^-1), triplet OCOCO (+99.4 kcal mol^-1), covalently bound triplet O<inf>2</inf>C-CO (+ 107.6 kcal mol^-1), singlet trioxapropellane (+171.9 kcal mol^-1) and triplet trioxapropellane (+ 222.4 kcal mol^-1). Of these, only triplet O<inf>2</inf>C-CO is accessible by vertical Franck-Condon one-electron oxidation of [O<inf>2</inf>C-CO]^-.. Neutralization reionization experiments of [O<inf>2</inf>C-CO]^-. (both ^-NR⁺ and ^-NR^-) fail to produce recovery signals corresponding to ionized C<inf>2</inf>O<inf>3</inf>, which means that if neutral C<inf>2</inf>O<inf>3</inf> is stable, the lifetime must be <10^-6 sec. The ^-NR⁺ spectrum of [O<inf>2</inf>C-CO]^-. shows peaks corresponding to CO^+., CO<inf>2</inf>^+. and to [O =C = C = O]^+.. The last of these species can only be formed from a decomposing C<inf>2</inf>O<inf>3</inf>^+. radical cation by a process endothermic by 47 kcal mol^-1 [at the CCSD-(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory]. Calculations at this same level of theory indicate that the vertical one-electron oxidation of [O<inf>2</inf>C-CO]^-. to triplet O<inf>2</inf>C-CO ground state produces the neutral with essentially no excess energy. There are two dissociation pathways of this triplet neutral, (i) an endothermic process yielding ³CO + ^-CO<inf>2</inf> (+ 28.9 kcal mol^-1), and (ii) an exothermic process (-6.8 kcal mol^-1) with a barrier of 5.4 kcal mol^-1 yielding ¹CO + ³CO<inf>2</inf>. A combination of experimental and theoretical data, suggests that vertical oxidation of [O<inf>2</inf>C-CO]^-. produces only one neutral C<inf>2</inf>O<inf>3</inf> isomer; a transient triplet O<inf>2</inf>C-CO neutral whose lifetime is less than 10^-6 sec.enJournal article002001032610.1021/jp012331j0001720489000192-s2.0-003582994162077