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Development of Aldehyde Functionalized Iridium(III) Complexes Photosensitizers with Strong Visible-Light Absorption for Photocatalytic Hydrogen Generation from Water
oleh: Xiao Yao, Qian Zhang, Po-Yu Ho, Sze-Chun Yiu, Songwut Suramitr, Supa Hannongbua, Cheuk-Lam Ho
Format: | Article |
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Diterbitkan: | MDPI AG 2023-03-01 |
Deskripsi
Four iridium(III) dyes functionalized with aldehyde functional group in the cyclometalating (C^N) ligands, bearing either diethyl [2,2′-bipyridine]-4,4′-dicarboxylate or tetraethyl [2,2′-bipyridine]-4,4′-diylbis(phosphonate) anchoring groups, coded as <b>Ir1</b>–<b>Ir4</b>, are synthesized and explored as photosensitizers. The synthetic route is described and all of the complexes are characterized with respect to their electrochemical and photophysical properties. Density functional theory (DFT) calculation was used to gain insight into the factors responsible for the photocatalytic properties of <b>Ir1</b>–<b>Ir4</b> as effective photosensitizers for photocatalytic hydrogen generation. Relative to common iridium(III) dyes, such as <b>[Ir(ppy)<sub>2</sub>(dcbpy)]<sup>+</sup></b> (ppy = 2-phenylpyridine), the absorption spectra of our dyes are broader, which is attributed to the extended π-conjugation in their C^N ligands. All of the new iridium(III) dyes were used as photosensitizers for visible-light driven hydrogen production by attaching to platinized TiO<sub>2</sub> nanoparticles (Pt–TiO<sub>2</sub>) in the presence of sacrificial electron donor (SED) of ascorbic acid (AA) in a purely aqueous solution. A H<sub>2</sub> turnover number (TON) up to 5809 was demonstrated for 280 h irradiation. Complexes with tetraethyl [2,2′-bipyridine]-4,4′-diylbis(phosphonate) anchoring groups were found to outperform those with classical diethyl [2,2′-bipyridine]-4,4′-dicarboxylate, which may be one of the important steps in developing high-efficiency iridium(III) photosensitizers in water splitting hydrogen generation.