Singlet excited-state dynamics of 5-fluorocytosine and Cytosine: an experimental and computational study.

ABSTRACT: The photophysics of singlet excited 5-fluorocytosine (5FC) was studied in steady-state and time-resolved experiments and theoretically by quantum chemical calculations. Femtosecond transient absorption measurements show that replacement of the C5 hydrogen of cytosine by fluorine increases the excited-state lifetime by 2 orders of magnitude from 720 fs to 73 +/- 4 ps. Experimental evidence indicates that emission in both compounds originates from a single tautomeric form. The lifetime of 5FC is the same within experimental uncertainty in the solvents ethanol and dimethyl sulfoxide. The insensitivity of the S(1) lifetime to the protic nature of the solvent suggests that proton transfer is not the principal quenching mechanism for the excited state. Excited-state calculations were carried out

SUBMITTER: Blancafort L 

PROVIDER: S-EPMC1660529 | biostudies-literature | 2005 May

REPOSITORIES: biostudies-literature