title: Chromophoric Dyads for the Light-Driven Generation of Hydrogen: Investigation of Factors in the Design of Multicomponent Photosensitizers for Proton Reduction.
abstract: Two new dyads have been synthesized and studied as photosensitizers for the light-driven generation of H2 from aqueous protons. One of the dyads, Dy-1, consists of a strongly absorbing Bodipy (dipyrromethene-BF2) dye and a platinum diimine benzenedithiolate (bdt) charge transfer (CT) chromophore, denoted as PtN2S2. The two components are connected through an amide linkage on the bdt side of the PtN2S2 complex. The second dyad, Dy-2, contains a diketopyrrolopyrrole dye that is linked directly to the acetylide ligands of a Pt diimine bis(arylacetylide) CT chromophore. The two dyads, as well as the Pt diimine bis(arylacetylide) CT chromophore, were attached to platinized TiO2 via phosphonate groups on the diimine through sonication of the corresponding esters, and each system was examined for photosensitizer effectiveness in photochemical generation of H2 from aqueous protons and electrons supplied by ascorbic acid. Of the three photosensitizers, Dy-1 is the most active under 530 nm radiation with an initial turnover frequency of 260 h(-1) and a total of 6770 turnovers over 60 h of irradiation. When a "white" LED light source is used, samples with Dy-2 and the Pt diimine bis(arylacetylide) chromophore, while not as effective as Dy-1, perform relatively better. A key conclusion is that the presence of a strongly absorbing organic dye increases dyad photosensitizer effectiveness only if the energy of the CT excited state lies below that of the organic dye's lowest excited state; if not, the organic dye does not improve the effectiveness of the CT chromophore for promoting electron transfer and the light-driven generation of H2. The nature of the spacer between the organic dye and the charge transfer chromophore also plays a role in the effectiveness of using dyads to improve light-driven energy-storing reactions.
authors.affiliation: Department of Chemistry, University of Rochester , Rochester, New York 14627, United States.|Institute of Molecular Functional Materials, Department of Chemistry, and Institute of Advanced Materials, Hong Kong Baptist University , Waterloo Road, Kowloon Tong, Hong Kong, P. R. China.|HKBU Institute of Research and Continuing Education, Shenzhen Virtual University Park , Shenzhen 518057, P. R. China.
authors.forename: Po-Yu
authors.initials: PY
authors.lastname: Ho
authors.affiliation: Department of Chemistry, University of Rochester , Rochester, New York 14627, United States.
authors.forename: Bo
authors.initials: B
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, University of Rochester , Rochester, New York 14627, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Mark
authors.affiliation: Institute of Molecular Functional Materials, Department of Chemistry, and Institute of Advanced Materials, Hong Kong Baptist University , Waterloo Road, Kowloon Tong, Hong Kong, P. R. China.|HKBU Institute of Research and Continuing Education, Shenzhen Virtual University Park , Shenzhen 518057, P. R. China.
authors.forename: Wai-Yeung
authors.initials: WY
authors.lastname: Wong
authors.affiliation: Department of Chemistry, University of Rochester , Rochester, New York 14627, United States.
authors.forename: David W
authors.initials: DW
authors.lastname: McCamant
authors.affiliation: Department of Chemistry, University of Rochester , Rochester, New York 14627, United States.
authors.forename: Richard
authors.initials: R
authors.lastname: Eisenberg