Photoinduced Charge-Transfer Dehydrogenation in a Gas-Phase Metal-DNA Base Complex:  Al-cytosine

Pedersen, David Bue; Zgierski, Marek Z.; Denommée, Stephane; Simard, Benoît

doi:10.1021/ja0122501

Cited by 22 publications

(41 citation statements)

References 48 publications

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“…For Al-cytosine, dehydrogenation is also observed to occur over a wide range of wavelengths. 1 The fact that significant amounts of dehydrogenated metal-base complexes are observed at many wavelengths, above the threshold energy, indicates that nonradiative relaxation from the initially excited states to the dissociative state are efficient consistent with the high density of states, as seen in Figure 6. Efficient nonradiative relaxation to lower energy electronic states is consistent with solution-phase data where lifetimes of excited states of the DNA bases can be less than a few picoseconds.…”

Section: The Dehydrogenation Mechanismmentioning

confidence: 69%

“…This peak corresponds to dehydrogenated Al-guanine. Using this technique the threshold for dehydrogenation of Al-cytosine, 1 as well Al-guanine, Mn-guanine, and Al-guanine-cytosine have been determined. These results are collected in Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…The geometries of the complexes are shown in Figure 5, as have been published elsewhere. 1,20 In Figure 6, potential energy curves of the lowest eight electronic states of cytosine and the lowest eleven for Alcytosine are shown as a function of N-H separation, where N is the ring-constituent nitrogen. To generate these plots, the geometries of the molecules were frozen in their lowest-energy, ground-state configurations except for the N-H bond length which was varied.…”

Section: The Dehydrogenation Mechanismmentioning

confidence: 99%

“…Theoretical structures of the ground states of neutral Alcytosine and Al-guanine. 1,20 Unlabeled atoms are carbon. absorption of a second photon that ionizes the dehydrogenated species.…”

Section: The Dehydrogenation Mechanismmentioning

confidence: 99%

“…16,17,18 In previous work we acquired the photoionization efficiency spectrum of an Al-cytosine complex. 1 This molecule was found to display photochemistry very different from that of cytosine. In particular, relatively efficient two-photon dehydrogenation of the complex was observed.…”

Section: Introductionmentioning

confidence: 99%

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Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

2003

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Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=b405da9f-ea27-430e-b6b0-4e0a077682c3 http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=b405da9f-ea27-430e-b6b0-4e0a077682c3 Sciences, National Research Council of Canada, Ottawa, Ontario, Canada, K1A 0R6 ReceiVed: March 28, 2003; In Final Form: May 22, 2003 Photoinduced dehydrogenations of gas-phase Al-guanine, Mn-guanine, and the Al-base pair adduct Alguanine-cytosine have been observed. Upper and lower limits on the minimum photon energy required to effect the dehydrogenation have been determined for these species. Species were generated using a laser ablation source and were detected with laser photoionization/time-of-flight mass spectrometry. Only metalated species were observed to dehydrogenate, and the effect of metal on the photochemistry of guanine and cytosine has been investigated using density functional theory (DFT). Avoided crossings between the ground and first electronically excited states are features specific to the metalated species and are likely responsible for the metal-specific dehydrogenation observed. The rapid nonradiative relaxation believed to manifest the dehydrogenation is consistent with the dominance of multiphoton contributions to the mass spectral signals observed which also stems from rapid nonradiative relaxation. In this context, the photophysics of the gasphase complexes is similar to that of solution-phase bases where nonradiative relaxation processes also dominate. Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-

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Section: The Dehydrogenation Mechanismmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 99%

Section: The Dehydrogenation Mechanismmentioning

confidence: 99%

“…Theoretical structures of the ground states of neutral Alcytosine and Al-guanine. 1,20 Unlabeled atoms are carbon. absorption of a second photon that ionizes the dehydrogenated species.…”

Section: The Dehydrogenation Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

2003

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Gas‐Phase Cation Affinity and Basicity Scales

Laurence

Gal

2009

Lewis Basicity and Affinity Scales

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The study of the formation of complexes between cations and chemical species in the gas phase offers the unique possibility of measuring the intrinsic (i.e. free of solvent and counter ion influences) Lewis basicity of these species. Although the charge-transfer component of the interaction energy in cation adducts is normally smaller than the electrostatic and polarization components, gas-phase cations are generally considered as archetypal Lewis acids because the full positive charge of the naked cation allows strong binding with classical Lewis bases. In fact, almost any entity bearing some electron density, such as the rare gases, can form complexes with cations that may be observable in the gas phase.There is a large array of cations that have been studied in the gas phase for their interaction with Lewis bases (generally neutral organic molecules) and are still being actively investigated today. The most studied is the proton [1-6]. This special cation will not be dealt with in this chapter (however, see Section 1.3 in Chapter 1), since the proton and its transfer serve to define the Brönsted acids and bases, as opposed to Lewis acids and bases, which do not exchange protons. Moreover, although the proton and a cation with an empty orbital may be seen as identical from the point of view of the Lewis theory, the special 'electronic structure' of the proton (in fact the absence of any electron) makes the proton affinity and basicity scales completely different, qualitatively and quantitatively, from any other cation scales. A significant part of the studies of the interaction of gas-phase metal cations with organic molecules was devoted to their chemical reactivity: bond insertion, bond cleavage, elimination and so on. This aspect is not considered here, although some of these reactions may be used as indirect routes for the formation of cation/molecule adducts.Apart from the proton, experimental studies have focused primarily on the binding of alkali metal cations and transition metal monocations. Few studies have considered alkaline Lewis Basicity and Affinity Scales: Data and Measurement

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Association of Cu²⁺with Uracil and Its Thio Derivatives: A Theoretical Study

et al. 2004

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The structures and relative stabilities of the complexes between Cu2+ and uracil, 2-thiouracil, 4-thiouracil, and 2,4-dithiouracil were investigated by B3LYP/6-311+G(2df,2p)//B3LYP/6-31G* DFT calculations. In those systems in which both types of basic centers, that is, a carbonyl and a thiocarbonyl group, are present, association of Cu2+ with the oxygen atom is systematically favored, in contrast to what was found for the corresponding Cu+ complexes. This can be understood by considering that association of Cu2+ is immediately followed by oxidation of the base, which accumulates the negative charge at the oxygen atoms. Similarly, for 2,4-dithiouracil the most basic site for Cu+ attachment is the sulfur atom at the 4-position, while for association of Cu2+ it is sulfur at the 2-position. In contrast, differences between uracil-Cu+ and uracil-Cu2+ complexes are very small, and in both cases the oxygen atom at the 4-position is the most basic. Cu2+ binding energies are about 4 and 1.2 times larger than Cu+ binding energies and proton affinities, respectively. Uracil- and thiouracil-Cu2+ complexes are thermodynamically unstable but kinetically stable with respect to their dissociation into uracil*+ + Cu+ or thiouracil*+ + Cu+. The Cu2+ binding energies vary with the difference between the second ionization potential of the metal and the first ionization potential of the base. regardless of the reference acid (H+, Cu+, Cu2+) the basicity trend is 2,4-dithiouracil > 4-thiouracil > 2-thiouracil > uracil.

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Photoinduced Charge-Transfer Dehydrogenation in a Gas-Phase Metal-DNA Base Complex: Al-cytosine

Cited by 22 publications

References 48 publications

Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

Gas‐Phase Cation Affinity and Basicity Scales

Association of Cu²⁺with Uracil and Its Thio Derivatives: A Theoretical Study

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Photoinduced Charge-Transfer Dehydrogenation in a Gas-Phase Metal-DNA Base Complex: Al-cytosine

Cited by 22 publications

References 48 publications

Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

Gas‐Phase Cation Affinity and Basicity Scales

Association of Cu2+with Uracil and Its Thio Derivatives: A Theoretical Study

Contact Info

Product

Resources

About

Association of Cu²⁺with Uracil and Its Thio Derivatives: A Theoretical Study