A Mononuclear [PtCl(tpy)]PF6 Complex for a Yellow Emitting Solution-Processable Organic Light Emitting Diode

We report square planar mononuclear Pt(II)-complexes of terpyridines in the form of [PtCl(L1/L2)]PF6 as phosphorescent emitters (where L1 = 4-(3-pyridine)2,2':6',2''-terpyridine and L2 = 4'-(3-pyridinyl)-4,4''-di(tert-butyl)-2,2':6'2''-terpyridine). Complex 2 showed emission at 534 nm in the DCM solution with photoluminescence quantum efficiency (ΦPL) = 14%, while in the mCBP host (5-wt % doped), the emission shifted to 584 nm with ΦPL = 37.8% and a phosphorescence lifetime (τphos) of 37.8 μs. Complex 2 in mCBP was used to fabricate a solution-processed phosphorescent organic light-emitting diode (PhOLED) which showed maximum external quantum efficiency (EQEmax) = 7.4% with yellow emission at λEL = 570 nm and exhibited a low efficiency roll-off with an EQE drop to 7.0% at 1000 cd/m2.

Pt(II)-bis(quinolinyl) complexes for photocatalytic hydrogen production

Three Pt(II)-bis(quinolinyl) complexes with varying electron densities were synthesized, structurally characterized and used for photocatalytic hydrogen production under different conditions. All the complexes were found to be active for hydrogen production giving a maximum turnover number (TON) of 1230 surpassing the conventionally used Pt-terpyridyl complexes.

Theoretical study on the mechanism of the hydrogen evolution reaction catalyzed by platinum subnanoclusters

The smallest subnanocluster models of platinum colloid (Pt_n) are supposed to diffuse in aqueous media in order to examine their behaviors when they are subjected to the electrocatalytic hydrogen evolution reaction under zero overpotential conditions at pH 0. The DFT approach allows us to clarify the nature of individual proton transfer (PT) and electron transfer (ET) processes together with the importance of relying on concerted proton-electron transfer (CPET) pathways to promote the majority of H* adsorption processes by Pt_n subnanoclusters. Although the CPET processes are closely correlated with the Volmer steps (Pt + H⁺ + e^- → Pt-H*) described so far in electrochemistry, our study for the first time points out the essential capability of the Pt_n clusters to promote the multiple PT steps without the need to transfer any electrons, revealing the fundamentally high basicity of the naked Pt_n clusters (pK_a = 27-28 for Pt₄, Pt₅, and Pt₆). The discrete cluster models adopted herein avoid the structural constraints forced by the standard slab models and enable us to discuss the drastic alterations in the geometric and electronic structures of the intermediates given by the consecutive promotion of multiple CPET steps. The weakening of the Pt-H* bond strength with the increasing number of CPET steps is well rationalized by carefully examining the changes in the ν(Pt-H*) vibrational frequencies, the hydricity, and the H₂ desorption energy. The behaviors are also correlated with the underpotential and overpotential deposited hydrogen atoms (H_UPD and H_OPD) discussed in electrochemical studies for many years.

Enhanced photoreduction of water catalyzed by a cucurbit[8]uril-secured platinum dimer

A cucurbit[8]uril (CB[8])-secured platinum terpyridyl chloride dimer was used as a photosensitizer and hydrogen-evolving catalyst for the photoreduction of water. Volumes of produced hydrogen were up to 25 and 6 times larger than those obtained with the corresponding free and cucurbit[7]uril-bound platinum monomer, respectively, at equal Pt concentration. The thermodynamics of the proton-coupled electron transfer from the Pt(ii)–Pt(ii) dimer to the corresponding Pt(ii)–Pt(iii)–H hydride key intermediate, as quantified by density functional theory, suggest that CB[8] secures the Pt(ii)–Pt(ii) dimer in a particularly reactive conformation that promotes hydrogen formation.

The cucurbit[8]uril macrocycle can secure a platinum terpyridyl complex into a particularly reactive dimer that catalyzes the photoreduction of water.

Design and photophysical studies of iridium(iii)–cobalt(iii) dyads and their application for dihydrogen photo-evolution

We report several new dyads constituted of cationic iridium(iii) photosensitizers and cobalt(iii) catalyst connected via free pendant pyridine on the photosensitizers.

Hydrogel-Embedded Model Photocatalytic System Investigated by Raman and IR Spectroscopy Assisted by Density Functional Theory Calculations and Two-Dimensional Correlation Analysis

The presented study reports the synthesis and the vibrational spectroscopic characterization of different matrix-embedded model photocatalysts. The goal of the study is to investigate the interaction of a polymer matrix with photosensitizing dyes and metal complexes for potential future photocatalytic applications. The synthesis focuses on a new rhodamine B derivate and a Pt(II) terpyridine complex, which both contain a polymerizable methacrylate moiety and an acid labile acylhydrazone group. The methacrylate moieties are afterward utilized to synthesize functional model hydrogels mainly consisting of poly(ethylene glycol) methacrylate units. The pH-dependent and temperature-dependent behavior of the hydrogels is investigated by means of Raman and IR spectroscopy assisted by density functional theory calculations and two-dimensional correlation spectroscopy. The spectroscopic results reveal that the Pt(II) terpyridine complex can be released from the polymer matrix by cleaving the C═N bond in an acid environment. The same behavior could not be observed in the case of the rhodamine B dye although it features a comparable C═N bond. The temperature-dependent study shows that the water evaporation has a significant influence neither on the molecular structure of the hydrogel nor on the model photocatalytic moieties.

A Bisamide Ruthenium Polypyridyl Complex as a Robust and Efficient Photosensitizer for Hydrogen Production

A photosensitizer based on a ruthenium complex of a bisamide-polypyridyl ligand gives rise to a large improvement in photocatalytic stability, rate of activity, and efficiency in photocatalytic H₂ production compared to [Ru(bpy)₃ ]²⁺ (bpy=2,2'-bpyridine). The bisamide ruthenium polypyridyl complex combined with a cobaltoxime-based photocatalyst was found to be highly efficient under blue-light (turnover number (TON)=7800) and green-light irradiation (TON=7200) whereas [Ru(bpy)₃ ]²⁺ was significantly less effective with a TON of 2600 and 1100, respectively. The greatest improvement was under red-light-emitting diodes, with bisamide ruthenium polypyridyl complex and cobaltoxime exhibiting a TON of 4200 compared to [Ru(bpy)₃ ]²⁺ and cobaltoxime at a TON of only 71.

A Nickel Dithiolate Water Reduction Catalyst Providing Ligand-Based Proton-Coupled Electron-Transfer Pathways

A nickel pyrazinedithiolate ([Ni(dcpdt)₂ ]^2- ; dcpdt=5,6-dicyanopyrazine-2,3-dithiolate), bearing a NiS₄ core similar to the active center of [NiFe] hydrogenase, is shown to serve as an efficient molecular catalyst for the hydrogen evolution reaction (HER). This catalyst shows effectively low overpotentials for HER (330-400 mV at pH 4-6). Moreover, the turnover number of catalysis reaches 20 000 over the 24 h electrolysis with a high Faradaic efficiency, 92-100 %. The electrochemical and DFT studies reveal that diprotonated one-electron-reduced species (i.e., [Ni^II (dcpdt)(dcpdtH₂ )]^- or [Ni^II (dcpdtH)₂ ]^- ) forms at pH<6.4 via ligand-based proton-coupled electron-transfer (PCET) pathways, leading to electrocatalytic HER without applying the highly negative potential required to generate low-valent nickel intermediates. This is the first example of catalysts exhibiting such behavior.

Photochemical H2 evolution from water catalyzed by a dichloro(diphenylbipyridine)platinum(ii) derivative tethered to multiple viologen acceptors

Enhanced hydrogen evolution from water photocatalyzed by a dichloro(diphenylbipyridine)platinum(ii) derivative tethered to multiple viologen acceptors is reported.

Improved photocatalytic hydrogen evolution driven by chloro(terpyridine)platinum(ii) derivatives tethered to a single pendant viologen acceptor

Chloro(terpyridine)platinum(ii) derivatives tethered to a single pendant viologen acceptor exhibit drastically improved turnover number in the photocatalytic H₂ evolution reaction from water.

Pt(ii)-Catalyzed photosynthesis for H2 evolution cycling between singly and triply reduced species

A platinum(ii)-based single-component molecular photocatalyst for hydrogen evolution from water cycling between the singly and triply reduced forms is reported.