title: Photochemical processes induced by the irradiation of 4-hydroxybenzophenone in different solvents.
abstract: The singlet and triplet excited states of 4-hydroxybenzophenone (4BPOH) undergo deprotonation in the presence of water to produce the anionic ground-state, causing fluorescence quenching and photoactivity inhibition. The same process does not take place in an aprotic solvent such as acetonitrile. In acetonitrile, 4BPOH is fluorescent (interestingly, one of its fluorescence peaks overlaps with peak C of humic substances), it yields singlet oxygen upon irradiation and induces the triplet-sensitised transformation of phenol (with a rate constant of (6.6 ± 0.3) × 10(7) M(-1) s(-1) (μ ± σ) between phenol itself and a triplet 4BPOH). The 4BPOH shows an intermediate behaviour in a partially protic solvent such as 2-propanol, where some deprotonation of the excited states is observed. In acetonitrile/2-propanol mixtures (at least up to 50% of 2-propanol) there is also some evidence of alcohol oxidation by the 4BPOH triplet state, while the experimental data are silent concerning such a possibility in pure 2-propanol. Considering that benzophenones are important components of chromophoric dissolved organic matter (CDOM) in surface waters, the present findings could have significance for the photoactivity of the hydrophilic surface layers vs. the hydrophobic cores of CDOM.
authors.affiliation: Dipartimento di Chimica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Barsotti
authors.affiliation: Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.
authors.forename: Marcello
authors.initials: M
authors.lastname: Brigante
authors.affiliation: Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Sarakha
authors.affiliation: Dipartimento di Chimica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy.
authors.forename: Valter
authors.initials: V
authors.lastname: Maurino
authors.affiliation: Dipartimento di Chimica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Minero
authors.affiliation: Dipartimento di Chimica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy and Centro NatRisk, Via L. Da Vinci 44, 10095 Grugliasco (TO), Italy. marcello.brigante@univ-bpclermont.fr davide.vione@unito.it.
authors.forename: Davide
authors.initials: D
authors.lastname: Vione