Photocatalytic Hydrogen Production Using a Red-Absorbing Ir(III)–Co(III) Dyad

Abstract

The synthesis of a Ir(III)-Co(III) dyad with vectorial electron transfer afforded a novel supramolecular system that photocatalytically produces hydrogen in a range extending from the blue region of the spectrum to the red region with higher turnover number and frequency compared to other bimetallic dyads.

Towards Noble‐Metal‐Free Dyads: Ground and Excited State Tuning by a Cobalt Dimethylglyoxime Motif Connected to an Iron N‐Heterocyclic Carbene Photosensitizer

“…Figure S1–7). This can be attributed to a small electron withdrawing effect of the cobalt fragment, which has also been found for related bimetallic iridium‐cobalt systems , . In contrast, 2 shows a significantly stronger bathochromic shift by 33 nm compared to non‐methylated 1 , since π‐accepting capabilities of the polypyridyl ligand increase.…”

Photocatalytic Hydrogen Evolution Driven by a Heteroleptic Ruthenium(II) Bis(terpyridine) Complex

“…Numerous studies using ruthenium, as well as iridium or rhenium photosensitizers showed that the presence of interactions between the photosensitizer and the catalyst leads to an enhancement of the overall photocatalytic activity. [4][5][6][7] Recently, Mulfort and Tiede suggested that a photosensitizer capable of coordinating to the catalytic center could overcome diffusional constraints and enable efficient intermolecular electron transfer. Even though they did not observe activity in hydrogen production for their systems, their investigations and results confirm this to be a promising approach.…”

A Heterobimetallic AuIII‐PtII Photocatalyst for Water Reduction to Hydrogen

“…The absorption band of 1 extends beyond 400 nm and tails into the visible region, which may be mainly attributed to the metal/ligand‐to‐ligand charge transfer (MLLCT) from dπ(Au‐C^N^C) to π*(terpy) by analogy with structurally related compounds . Compared with the absorption spectra of individual components 2 and 3 , the absorption spectrum of 1 was shifted to a lower energy with enhanced absorptivity in the visible region, suggesting the presence of electronic communications between the two metallic centers via the bridge ligand in the ground state . This behavior could be due to a change in orbital energies upon the introduction of the second metal coordination.…”

“…[14] Compared with the absorption spectra of individual components 2 and 3,the absorption spectrum of 1 was shifted to al ower energy with enhanced absorptivity in the visible region, suggesting the presenceo fe lectronic communications between the two metallicc enters via the bridge ligand in the ground state. [15] This behavior could be due to ac hange in orbital energies upon the introduction of the second metal coordination.A ss hown in Figure 2( right), upon photoexcitation, the emission spectrumo f1 was as ingle, broad and unstructured emission profile with ap eak at approximately 657 nm, which was mainly derived from the lowest-lying triplet state (T 1 ), consisting of contributions from charge transfer in the 3 MLCT (dp(Pt)!p*(terpy))a nd 3 LLCT (p!p*) states, according to results previously reportedf or the corresponding complexes. [16] The emissionm aximum showed ar edshift with respect to parentm ononuclear complexes 2 (503 nm) and 3 (604 nm).…”

“…[23] However, complex 1 exhibited rather low TON compared to many other supramolecule catalysts, [14a, 24] probablyd ue to its shorter emission lifetime. According to the relative reports,t he excited state lifetimes of reported bimetallic complexesa re usually multiples event en times of that of 1, [15] enabling the proceeding of the slow photochemical processes. [18b] Additionally,t he quenching constant (k q )o f1 is about one or two orders of magnitude lower than other systems, [25] indicating some of the difficulties of electron transfer between 1 and sacrificial agent.…”