Determination of electron affinity on the base of experimentally measured lifetime of negative molecular ions of coumarin derivatives

Resonance attachment of low-energy (0-15 eV) electrons to molecules of 4.7- and 6.7-dihydroxycoumarin has been investigated by means of negative ion mass spectrometry. These natural compounds possess biological activity associated with antioxidant and bactericidal properties. The most probable- -- - -structures of fragment negative ions ([M H]-, [M 2H]-, [M CO]-, [M COH]-, [M COOH]-, etc.) have been predicted by means of analysis of decay channels for molecular negative ions using the results of the densityfunctional theory calculations. Mean lifetime for molecular negative ions of 4.7-dihydroxycoumarin relative to electron autodetachment has been measured. The adiabatic electron affinity (𝐸𝐴𝑎) has been estimated in the framework ofthe Arrhenius approximation. It has been found that values calculated atB3LYP/6-31+G(d) level with minimal addition of diffuse functions as a differencebetween the total energies of a neutral molecule and its radical anion correlate with experimental values.