Synthesis and Characterization of New Iridium Photosensitizers for Catalytic Hydrogen Generation from Water

Abstract

Novel phenylazole ligands were applied successfully in the synthesis of cyclometalated iridium(III) complexes of the general formula [Ir(phenylazole)(2)(bpy)]PF(6) (bpy=2,2'-bipyridine). All complexes were fully characterized by NMR, IR, and MS spectroscopic studies as well as by cyclic voltammetry. Three crystal structures obtained by X-ray analysis complemented the spectroscopic investigations. The excited-state lifetimes of the iridium complexes were determined and showed to be in the range of several hundred ns to multiple µs. All obtained iridium complexes were active as photosensitizers in catalytic hydrogen evolution from water in the presence of triethylamine as a sacrificial reducing agent. Applying an in situ formed iron-based water reduction catalyst derived from [HNEt(3)](+) [HFe(3)(CO)(11)](-) and tris[3,5-tris-(trifluoromethyl)-phenyl]phosphine as the ligand, [Ir(2-phenylbenz-oxazole)(2)-(bpy)]PF(6) proved to be the most efficient complex giving a quantum yield of 16% at 440 nm light irradiation.

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

“…Then, PS •+ can react with the electron donor D ( k red ) to regenerate the PS ground state (photocyclic reaction), leading to the formation of one radical cation D •+ . Generally, A •− and D •+ will give rise to initiating radicals for free radical polymerization, to hydrogen by water reduction or oxygen by water oxidation [6–8], etc. In an ideal case, a photocatalytic behavior is ensured when there is enough redox donor to make the dye surviving during a long period of time.…”

“…As a part of this research area, the development of photoradical generators (PRG) is still a lively topic that finds applications in triggering bioactivity [1], drug or fragrance release [2–4], microelectronics [5], water catalysis reduction [6–8], and laser imaging [9]. In organic chemistry, the development of new methods for organic synthesis was achieved by use of photolabile protective groups, which could be released under irradiation by light [10–11].…”

Blue-green emitting cationic iridium complexes with 1,3,4-oxadiazole cyclometallating ligands: synthesis, photophysical and electrochemical properties, theoretical investigation and electroluminescent devices

“…[33][34][35] Such an approach seems more appealing than the commonly used F substitution, 24 as C-F bonds are reactive and tend to rupture upon excitation of the complex. 39,40 Recently, both oxd-type CΛN and NΛN ligands have been combined in single complexes, which, however, give yellow to red light emission, largely owing to the low LUMO levels associated with the NΛN ligands. 39,40 Recently, both oxd-type CΛN and NΛN ligands have been combined in single complexes, which, however, give yellow to red light emission, largely owing to the low LUMO levels associated with the NΛN ligands.…”

Chemical Tuning and Absorption Properties of Iridium Photosensitizers for Photocatalytic Applications

“…In the present work, we have explored ground and excited state properties of a series of Ir-based photosensitizers, which are derivatives of the parent IrPS extensively investigated before in catalytic, spectroscopic, and theoretical studies [11,[21][22][23][24][25][26][27][28][29][30][31][32][33]. To facilitate an accurate description of the excited states, the optimally-tuned range-separated density functional approach has been chosen.…”