title: Photochemical studies of 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM).
abstract: Kinetic UV-VIS absorption data following 355 and 266 nm nanosecond laser flash photolysis of 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM) solutions is presented. The kinetics of the decay of the non-chelated enol (NCE) produced following 355 nm excitation of BM-DBM solutions are analysed in terms of mixed 1st- and 2nd-order kinetics. The temperature dependences of the component rate constants are unusual and both 1st- and 2nd-order components display negative activation energies, which are explained by invoking pre-equilibria. In addition, it is shown for the first time that 266 nm laser photolysis of BM-DBM solutions leads to formation of the triplet state of the keto (K) form with a lifetime of approximately 500 ns. Under these conditions the triplet state of the K form is quenched by oxygen.
authors.affiliation: School of Chemistry and Physics, Lennard-Jones Laboratories, Keele University, Staffordshire, ST5 5BG, UK.
authors.forename: A
authors.initials: A
authors.lastname: Cantrell
authors.forename: D J
authors.initials: DJ
authors.lastname: McGarvey
mesh_terms: D001565:Benzoates / Q000737:chemistry*; D047188:Chalcones; D007700:Kinetics; D007834:Lasers; D015394:Molecular Structure; D010777:Photochemistry; D010782:Photolysis; D011427:Propiophenones; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013473:Sunscreening Agents / Q000737:chemistry*; D013696:Temperature; D014050:Toluene / Q000737:chemistry
chemical_list: D001565:Benzoates; D047188:Chalcones; D011427:Propiophenones; D012996:Solutions; D013473:Sunscreening Agents; D014050:Toluene; C049935:avobenzone