The photogeneration and detection of new binol quinone methides undergoing mono- and bisalkylation of free nucleophiles was investigated by product distribution analysis and laser flash photolysis in water solution using binol quaternary ammonium derivatives as photoactivated precursors. The alkylation processes of N and S nucleophiles are strongly competitive with the hydration reaction. DNA cross-linking potency of the water-soluble binol quaternary ammonium salts was investigated as a pH function and compared to that of other quaternary ammonium salts capable of benzo-quinone methide photogeneration, by gel electrophoresis. DFT calculations in the gas phase and in water bulk on the binol and benzo quaternary ammonium salts 2 and 4 evidence structural and electrostatic features of the binol derivative which might offer a rationalization of its promising high photo-cross-linking efficiency.