Stacking-controlled phototransformations of the 5-fluorouracil residues in dinucleotide model compounds

5-Fluorouracil residues can form cyclobutane-type photodimers in a direct excitation stacking-controlled process. The stacking also has an important effect on the photohydration of uracil and 5-fluorouracil in our model compounds 5RUra(CH2)35FUra, where R = H, CH3, C2H5, C3H7, F or Cl.