A DFT study of the reactions of the Cu+ ion with methylamine and dimethylamine

The fragment ions Cu+(CH3N) and Cu+(C2H5N) have been detected in the recent experiment from the products of the ion-molecule reactions of the Cu+ ion with methylamine (MA, CH3NH2) and dimethylamine (DMA, (CH3)2NH) using the time-of-flight mass spectrum technology. Their forming mechanisms and the structural characteristics, however, are still not clear. Here, we show a detailed DFT study for the potential energy surfaces relevant for the reactions of the Cu+ ion with MA and DMA to address the concerned issues. We find that the ion-molecule reactions are driven by a large energy gain upon the association of the Cu+ ion with MA or DMA. A general dehydrogenation mechanism of MA and DMA promoted by the Cu+ ion has been shown, and the preponderant structures contributing to the recorded mass spectra for the product ions Cu+(CH3N) and Cu+(C2H5N) have been formulized as Cu+-CH2NH and Cu+-CH2NHCH2. The present study represents a prototype of the reaction of the Cu+ ion with amine, and the conclusion drawn out from this work is expected to provide a consistent view on the reactivity of this kind of reactions.