Site- and bond-selective H- formation in methylated pyrimidine bases driven by potassium-molecule collisions

Electron transfer in alkali-molecule collisions to gas phase thymine and uracil yielding H− formation is selectively controlled in the energy range between 5 and 65 eV. By tuning the collision energy, electron transfer from the alkali to methylated thymine (at the N1 position), methylated uracil (at the N3 position) and partly deuterated thymine, enables H−formation. Such process proceeds not only through the breaking of the (C-H) against (N-H) bonds but also through N1 against N3 sites. Such selectivity, as far as bond and site are concerned, is here reported for the first time in collision induced dissociation experiments by alkali-molecule interactions.