?Guanine Tautomerism in Ionic Complexes with Ag+ Investigated by IRMPD Spectroscopy and Mass Spectrometry?

A. CRUZ ORTIZ; F. L. MOLINA; P. MAITRE; G. A. PINO *

JOURNAL OF PHYSICAL CHEMISTRY B

American Chemical Society

Año: 2021 vol. 125 p. 7137 - 7146

1089-5647

In this paper, we present the IRMPD spectra ofthree ionic complexes between guanine (G) and silver (Ag+):[GAg-H2O]+, [GAgG]+ produced in the electrospray ionizationsource of the mass spectrometer, and [GAg]+ produced bycollision induced dissociation of the [GAgG]+ complex. On thebasis of the comparison of theoretically calculated IR spectra, weshow that there are two isomers of each complex containing twodifferent keto-amino (KA) tautomers of G (GKA(1,9) andGKA(1,7)). The observed isomers are the most stable structuresin aqueous solution, and their experimentally estimated relativepopulations are in better agreement with the calculated relativepopulations in solution than in the gas phase, both at 298 K. Weconcluded that these observations suggest that GKA(1,9) andGKA(1,7) coexist in solution according to previous theoretical reports (Colominas, C.; et al. J. Am. Chem. Soc. 1996, 118, 6811). Wewere unable to find any evidence of the presence of the GEA(9), GKA(3,7), GKA(3,9), or GKA(7,9), whose relative stabilities insolution are strongly dependent on the theoretical method used to account for the solvent effect (Hanus, M.; et al. J. Am. Chem. Soc.2003, 125, 7678).