Photochemical transformations of 4,6-dihydroxypyrimidine and 2-methyl-4,6-dihydroxypyrimidine isolated in low-temperature Ar, Ne and H2 matrices

Abstract

Monomers of 4,6-dihydroxypyrimidine and 2-methyl-4,6-dihydroxypyrimidine were trapped from the gas phase into low-temperature Ar, Ne and normal-H2 matrices. Dihydroxy and oxo-hydroxy tautomers were identified. The isolated monomers were exposed to UV (285 > λ > 270 nm) radiation. For the molecules isolated in Ar and Ne matrices, such UV excitation led to conversion of the oxo-hydroxy tautomer into three products: the dihydroxy form, the Dewar isomer and the open-ring ketene. In solid-hydrogen matrices, UV-induced oxo-hydroxy → dihydroxy hydrogen-atom-transfer conversion did not occur; the UV-excited oxo-hydroxy form of the investigated compounds transformed only to the Dewar and open-ring ketene products.