title: Photoinduced water splitting with oxotitanium porphyrin: a computational study.
abstract: The photochemistry of the hydrogen-bonded oxotitanium porphyrin-water complex (TiOP-H(2)O) has been explored with electronic-structure calculations. It is shown that intramolecular charge-transfer processes, which are initiated by the excitation of the Soret band of TiOP, accumulate electronic charge on the oxygen atom of TiOP, which in turn abstracts a hydrogen atom from water by an exoenergetic and essentially barrierless hydrogen-transfer reaction, resulting in the TiPOH˙-OH˙ biradical. About 75% of the absorbed photon energy is thus stored as chemical energy in two ground-state radicals. Absorption of a second photon by TiPOH˙ can result in the detachment of the H˙ radical and recovery of the photocatalyzer TiOP. Again, about 75% of the photon energy is stored in the dissociation energy of TiPOH˙. Overall, a water molecule is decomposed into H˙ and OH˙ radicals by the absorption of two visible photons. Exoenergetic radical recombination reactions can yield molecular hydrogen, molecular oxygen or hydrogen peroxide as closed-shell products.
authors.affiliation: Institute of Physics, Polish Academy of Sciences, PL-02668 Warsaw, Poland. sobola@ifpan.edu.pl
authors.forename: Andrzej L
authors.initials: AL
authors.lastname: Sobolewski
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Domcke
mesh_terms: D002384:Catalysis; D004583:Electrons; D006860:Hydrogen Bonding; D017785:Photons; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*
chemical_list: D011166:Porphyrins; D014867:Water; D014025:Titanium