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The role of Ag(I) ions in the electronic spectroscopy of adenine–cytosine mispairs: A MS-CASPT2 theoretical study

Paper ID Volume ID Publish Year Pages File Format Full-Text
28095 44059 2007 9 PDF Available
Title
The role of Ag(I) ions in the electronic spectroscopy of adenine–cytosine mispairs: A MS-CASPT2 theoretical study
Abstract

Adenine–cytosine (AC) mispairs have been theoretically studied with MS-CASPT2//CASSCF methods in the presence and absence of Ag ions. The electronically excited states of the most stable AC mispair in the reverse-Wobble (RW) conformation have been compared with those of different Ag(I)–AC complexes, including (i) metalated RW conformations, and (ii) the most stable structures in gas phase which contain the Ag ion bridging A and C. The spectra of these complexes are characterized by charge-transfer (CT) and strong locally excited (LE) states. The metal-to-metal, metal-to-ligand, and Rydberg transitions are very weak in comparison to the nucleobase transitions. Attending to the LE and CT states, and except for the shifts induced by the presence of the Ag, the electronic spectrum of metalated AC mispairs resembles the one of the RW, showing two intense LE bands around 4.5 and 5.5 eV, corresponding to transitions within the adenine and cytosine π-system, respectively. Additionally TD-DFT results obtained with the B3LYP functional are compared with MS-CASPT2//CASSCF calculations. The results clearly evidence the weakness of TD-DFT to describe long range exchange interactions leading to strongly underestimated CT states.

Keywords
DNA; Adenine; Cytosine; Silver; Excited states; CASPT2; TD-DFT
First Page Preview
The role of Ag(I) ions in the electronic spectroscopy of adenine–cytosine mispairs: A MS-CASPT2 theoretical study
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 190, Issues 2–3, 15 August 2007, Pages 301–309
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering