A Comparative Picosecond Transient Infrared Study of 1-Methylcytosine and 5'-dCMP That Sheds Further Light on the Excited States of Cytosine Derivatives

摘要

The role of N1-substitution in controlling the deactivation processes in photoexcited cytosine derivatives has been explored using picosecond time-resolved IR spec-troscopy. The simplest N1-substituted derivative, 1-methyl-cytosine, exhibits relaxation dynamics similar to the cytosine nucleobase and distinct from the biologically relevant nucleotide and nudeoside analogues, which have longer-lived excited-state intermediates. It is suggested that this is the case because the sugar group either facilitates access to the long-lived ~1noπ~* state or retards its crossover to the ground state.