title: Conjugation, Substituent, and Solvent Effects on the Photogeneration of Quinone Methides.
abstract: 4- and 5-arylethynyl water-soluble Mannich bases and related quaternary ammonium salts were synthesized and investigated as a model of conjugated quinone methide precursors (QMPs) by UV-vis light activation. Preparative photohydration and trapping reactions by thiols were studied, together with the detection of both transient QMs and competing QMP lowest triplet excited states (T1), by laser flash photolysis. The efficiency of the arylethynyl derivatives as QMPs was remarkably affected by structural features (i.e., conjugating arylethynyl moieties, substituents, and leaving groups) and protic vs aprotic solvation. Our collective data clarify the dichotomy in the photoreactivity of conjugated Mannich bases and related quaternary ammonium salts as alkylating agents and singlet oxygen sensitizers.
authors.affiliation: Dipartimento di Chimica, Università di Pavia , V.le Taramelli 10, 27100 Pavia, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Doria
authors.affiliation: Dipartimento di Chimica, Università di Pavia , V.le Taramelli 10, 27100 Pavia, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Lena
authors.affiliation: Dipartimento di Chimica, Università di Pavia , V.le Taramelli 10, 27100 Pavia, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Bargiggia
authors.affiliation: Dipartimento di Chimica, Università di Pavia , V.le Taramelli 10, 27100 Pavia, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Freccero