Photodissociation of gaseous metal ion-nucleobase complexes: Mg+-uracil and Mg+-thymine

Mg+-nucleobase complexes have been generated for the first time by a laser-ablation technique. Mg+-uracil and Mg+-thymine are studied by photodissociation and density functional theory calculations. The evaporative loss of Mg+ is found to be the dominant channel after photoexcitation. A number of photoproducts due to the nucleobase lesions have also been detected in the photon energy region of 3.4 eV, whereas only one of them is identified around 5.0 eV. The site of photoinduced C-N and/or C-C bond rupture is found to be at the carbonyl group where the metal is bound. A charge-transfer photoproduct is observed only from Mg+-thymine. (C) 2004 Elsevier B.V. All rights reserved