EXCITED-STATE PROTON-TRANSFER IN SYNTHETIC FLAVYLIUM SALTS - 4-METHYL-7-HYDROXYFLAVYLIUM AND 4',7-DIHYDROXYFLAVYLIUM - EXAMPLE OF A 4-LEVELMOLECULAR DEVICE TO INVERT THE POPULATION OF THE EXCITED-STATE

The excited state proton transfer (ESPT) observed in the compounds 4-m ethyl-7-hydroxyflavylium and 4',7-dihydroxyflavylium is described, and the results are quantitatively interpreted on the basis of the Weller approach. ESPT is especially efficient in the case of 4-methyl-7-hydr oxyflavylium. For pH > 2, proton recombination in the excited state do es not occur and the yield of the adiabatic formation of excited base (A) through the excited acid (AH(+)*) is 0.93. This result compares w ith 0.45 for 4',7-dihydroxyflavylium under identical conditions. The u se of adiabatic proton transfer to obtain the inversion of the populat ion of the excited state is discussed.