title: IRMPD action spectroscopy of alkali metal cation-cytosine complexes: effects of alkali metal cation size on gas phase conformation.
abstract: The gas-phase structures of alkali metal cation-cytosine complexes generated by electrospray ionization are probed via infrared multiple photon dissociation (IRMPD) action spectroscopy and theoretical calculations. IRMPD action spectra of five alkali metal cation-cytosine complexes exhibit both similar and distinctive spectral features over the range of ~1000-1900 cm(-1). The IRMPD spectra of the Li(+)(cytosine), Na(+)(cytosine), and K(+)(cytosine) complexes are relatively simple but exhibit changes in the shape and shifts in the positions of several bands that correlate with the size of the alkali metal cation. The IRMPD spectra of the Rb(+)(cytosine) and Cs(+)(cytosine) complexes are much richer as distinctive new IR bands are observed, and the positions of several bands continue to shift in relation to the size of the metal cation. The measured IRMPD spectra are compared to linear IR spectra of stable low-energy tautomeric conformations calculated at the B3LYP/def2-TZVPPD level of theory to identify the conformations accessed in the experiments. These comparisons suggest that the evolution in the features in the IRMPD action spectra with the size of the metal cation, and the appearance of new bands for the larger metal cations, are the result of the variations in the intensities at which these complexes can be generated and the strength of the alkali metal cation-cytosine binding interaction, not the presence of multiple tautomeric conformations. Only a single tautomeric conformation is accessed for all five alkali metal cation-cytosine complexes, where the alkali metal cation binds to the O2 and N3 atoms of the canonical amino-oxo tautomer of cytosine, M(+)(C1).
authors.affiliation: Department of Chemistry, Wayne State University, Detroit, MI, 48202, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: R R
authors.initials: RR
authors.lastname: Wu
authors.forename: N C
authors.initials: NC
authors.lastname: Polfer
authors.forename: G
authors.initials: G
authors.lastname: Berden
authors.forename: J
authors.initials: J
authors.lastname: Oomens
authors.forename: M T
authors.initials: MT
authors.lastname: Rodgers
mesh_terms: D002412:Cations / Q000737:chemistry; D003596:Cytosine / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D008672:Metals, Alkali / Q000737:chemistry*; D010316:Particle Size; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D002412:Cations; D005740:Gases; D008672:Metals, Alkali; D003596:Cytosine
references.citation: Phys Chem Chem Phys. 2007 Aug 7;9(29):3804-17
references.pmid: 17637973
references.citation: Inorg Chem. 1997 Apr 9;36(8):1583-1587
references.pmid: 11669746
references.citation: J Am Chem Soc. 2006 Jan 18;128(2):517-25
references.pmid: 16402839
references.citation: Nature. 1976 Sep 23;263(5575):285-9
references.pmid: 958482
references.citation: Dalton Trans. 2009 Jun 28;(24):4619-34
references.pmid: 19513468
references.citation: Chemphyschem. 2007 Oct 22;8(15):2235-44
references.pmid: 17910021
references.citation: J Phys Chem A. 2012 Apr 26;116(16):3989-99
references.pmid: 22452793
references.citation: Nature. 1970 Aug 8;227(5258):561-3
references.pmid: 4913914
references.citation: J Am Chem Soc. 2001 Oct 24;123(42):10272-9
references.pmid: 11603977
references.citation: Nature. 1953 May 30;171(4361):964-7
references.pmid: 13063483
references.citation: J Chem Inf Model. 2007 May-Jun;47(3):1045-52
references.pmid: 17428029
references.citation: Phys Chem Chem Phys. 2012 Apr 7;14(13):4517-26
references.pmid: 22361913
references.citation: Phys Chem Chem Phys. 2005 Sep 21;7(18):3297-305
references.pmid: 16240044