title: Guanine tetrads: an IRMPD spectroscopy, energy resolved SORI-CID, and computational study of M(9-ethylguanine)(4)(+) (M = Li, Na, K, Rb, Cs) in the gas phase.
abstract: The intrinsic properties of the alkali metal cationized G-tetrads, M(9eG)4(+) (M = Li, Na, K, Rb, Cs) composed of 9-ethylguanine (9eG), were studied by a combination of mass spectrometric techniques. The gas phase structures were probed by infrared multiple photon dissociation (IRMPD) spectroscopy in both the fingerprint region (900-1850 cm(-1)) and the N-H/C-H stretching region (2700-3800 cm(-1)). The gas phase structures were found to be similar for all five complexes and most consistent with the metal-centred G-tetrad structure. Energy-resolved CID was also used to compare the gas phase stabilities of the G-tetrads and showed that Na(9eG)4(+) was more stable than Li(9eG)4(+) followed by the K(+), Rb(+), and Cs(+) G-tetrads in order. The experimental energy ordering was reproduced by electronic structure calculations of the energies. Furthermore, the computations also showed that the lower stability to loss of 9-ethylguanine for the Li(+) complex could be due to a strong destabilization of the neutral G-tetrad due to the persistence toward maximizing the ion-dipole interactions while also maintaining hydrogen bonding interactions.
authors.affiliation: Department of Chemistry, Memorial University, St. John's, NL, CanadaA1B 3X7. tfridgen@mun.ca.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Azargun
authors.forename: Travis D
authors.initials: TD
authors.lastname: Fridgen
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D006860:Hydrogen Bonding; D013058:Mass Spectrometry / Q000379:methods; D008672:Metals, Alkali / Q000737:chemistry*; D008958:Models, Molecular; D013055:Spectrophotometry, Infrared / Q000379:methods
chemical_list: D056831:Coordination Complexes; D005740:Gases; D008672:Metals, Alkali; D006147:Guanine; C014542:9-ethylguanine