Deprotonation Dynamics of Local Anesthetics in Hydrophobic Media: Dibucainehci in Water/Alcohol or Surfactant Mixtures

The emitting chromophores, emitting states, state orderings and phosphorescence lifetimes of neutral, hydrogen‐bonded, and protonated dibucaines in water/alcohol mixtures were determined experimentally and were confirmed theoretically using a HAM/3 method. These photophysical properties are used to probe the deprotonation dynamics of dibucaine‐HCl in the water/hydrophobic media. It is found that the protonated dibucaine in an aqueous solution is deprotonated and/or forms hydrogen‐bonded dibucaine when it is brought into contact with the alcohols and surfactants. The observed deprotonation processes could lend some insight on the molecular basis of pharmacological action of dibucaine.