Fig. 1.

(a) PT PE curves obtained at the time-dependent B3LYP level, without excited-state geometry optimization (•) and with excited-state geometry optimization (compare text) (○) by using the 6–31G** basis set. (b) Fluorescence spectra of the 7AI dimers (Scheme 1) at 102 K. The spectra were obtained from independent anhydrous 2-methylbutane solutions. Spectrum F₁ (normal tautomer) was obtained from the deuterated 7AI dimer solution, and spectrum F₂ (PT tautomer) was recorded from the nondeuterated 7AI dimer solution. It is observed that deuteration hinders double-deuteron transfer.