Spin-forbidden F+ transfer between 2NF+ and CO: a computational study on the detailed mechanistic aspects Authors: Aschi, Massimilianoa; Grandinetti, Feliceb Affiliations: a. Dipartimento di Chimica, Universita` di Roma "La Sapienza", P. le A. Moro, 5, 00185, Roma, Italy

b. Dipartimento di Scienze Ambientali, Universita` della Tuscia, Via S. C. De Lellis, 01100, Viterbo, Italy

Abstract (English):

FULL TEXT

The detailed mechanistic aspects of the ion-molecule reaction between 2NF+ and CO with formation of 1FCO+ and 4N have been investigated by using density functional theory and ab initio calculations. We have first located on the ground doublet and quartet B3LYP/6-311+G(d) (N,F,C,O)+ potential energy surfaces the various energy minima and transition structures involved in this process, and subsequently located the minimum energy points lying on the B3LYP/6-311+G(d) line of intersection between the two surfaces by using a recently described steepest descent-based method [Theor. Chem. Acc. 99 (1998) 95]. The obtained results indicate that this "spin-forbidden" reaction is a viable process in the gas phase, and could occur by two alternative mechanisms. The first one consists of the formation of the (2NF+/CO) adduct 1 on the doublet (N,F,C,O)+ surface, which subsequently undergoes the spin-forbidden isomerization into the loosely bound adduct (4N/FCO+) adduct 5 on the quartet surface via a 1,2 fluorine shift from nitrogen to carbon. Isomer 5 undergoes in turn the barrier-free dissociation into the 4N and FCO+ reaction products. The second conceivable mechanistic route consists of the formation of the adduct 1 and its isomerization into the (2N/FCO+) adduct 7 via an adiabatic process. The eventual spin-forbidden formation of isomer 5 from isomer 7 occurs by a nonadiabatic 1,2 fluorine shift from nitrogen to carbon. Keywords: Fluorine; F+ transfer; Spin-forbidden; DFT; Ab initio