Photoinduced charge-transfer dehydrogenation in a gas-phase metal-DNA base complex: Al-cytosine

J Am Chem Soc. 2002 Jun 12;124(23):6686-92. doi: 10.1021/ja0122501.

Abstract

An Al-cytosine association complex has been generated via laser ablation of a mixture of aluminum and cytosine powders that were pressed into a rod form. The ionization energy of the complex is found to be 5.16 +/- 0.01 eV. The photoionization efficiency spectrum of Al-cytosine has also been collected. DFT calculations indicate that binding of Al to cytosine manifests a significant weakening of the N-H bond, predicted to have a strength of 1.5 eV in the complex, and a significant stabilization of the oxo tautomeric form relative to the hydroxy forms. The predicted ionization energy of 5.2 eV agrees well with the experimental value. The threshold for dehydrogenation/ionization of Al-cytosine, forming (Al-cytosine-H)+, is found to occur at photoexcitation energies between 11.4 and 12.8 eV. This is a two-photon process that is proposed to occur via photoinduced electron transfer from Al to an antibonding (sigma) orbital localized on N-H. In the context of this mechanism, this work constitutes the first time charge transfer between a metal and DNA base has been photoinitiated in the gas phase.

MeSH terms

  • Aluminum / chemistry*
  • Cytosine / chemistry*
  • DNA / chemistry*
  • Hydrogenation
  • Organometallic Compounds / chemistry
  • Photochemistry
  • Thermodynamics

Substances

  • Organometallic Compounds
  • Cytosine
  • DNA
  • Aluminum