Protonation kinetics of the triplet state of safranine in hydroxylic solvents

✍ Scribed by M.G. Neumann; J.C. Scaiano

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 359 KB
• Volume: 54
• Category: Article
• ISSN: 1010-6030
• DOI: 10.1016/1010-6030(90)87010-9

✦ Synopsis

Safranine in its ground state in the pH range from 2.5 to 6.0 is largely present in its monoprotonated form. Laser excitation followed by intersystem crossing leads to the triplet state. In the triplet state, the favorable species is the diprotonated form in this pH range. The rate constants for protonation can be readily determined by laser flash photolysis and lead to the conclusion that the process is somewhat slower than difFusion controlled in fluid solvents such as methanol, but considerably faster than the diffusion limit in viscous solvents such as ethylene glycol and glycerol. The behavior under these conditions is explained in terms of proton hopping through different solvent molecules.