Garry Shawn Hanan

We report here the synthesis of a new heteroleptic ruthenium–terpyridine complex that exhibits both high stability and enhanced photocatalytic activity with an increase of approximately one order of magnitude for the hydrogen evolution reaction coming from a strong push–pull effect. The complex demonstrates high performance under blue light (445 nm), achieving a turnover number (TON) above 3500 molH2 molPS–1 with sustained hydrogen production for over 6 days. That TON value is more than twice as high as that of the reference [Ru(bpy)3]2+ complex under the same conditions. Under red light (630 nm), this complex also shows high efficiency and stability with no significant decrease in the turnover frequency over 6 days, achieving a TON over 960 molH2 molPS-1, a value competitive with reference [Ru(bpy)3]2+ complex under blue light (this last showing no hydrogen evolution under red-light). We identified a kinetic competition between the main H2 production process and degradation reactions from the reduced complex species and could further enhance the sustainability of the system (under blue light) by increasing the cobalt catalyst concentration. A TON above 4100 molH2 molPS-1 could be reached after 8 days.

The persistent global energy crisis can be addressed by focusing on the advancement of cleaner energy sources. As a clean, efficient, and renewable option, hydrogen has long been regarded as a promising alternative to fossil fuels. Light-driven hydrogen evolution reaction (HER) offers a viable substitute for nonrenewable energy sources, since hydrogen is an energy-dense (143 MJ·kg–1) carbon-free fuel. In this respect, a handful of Pt(II) square-planar complexes, such as [Pt(II)(tpy)Cl]+ (where tpy = 2,2′:6′,2′′-terpyridine) have been reported in the literature for proton reduction, albeit with low turnover numbers (TONs) and a tendency to decompose to Pt nanoparticles. With these facts in mind, two Pt(II) terpyridyl complexes with varying electron densities were synthesized, structurally characterized, and successfully used for photocatalytic hydrogen production under different conditions (Pt catalyst + Ru photosensitizer, Co catalyst + Pt photosensitizer, and Pt photosensitizer + Pt catalyst) under varying light illumination. These complexes were found to be active for hydrogen production without the formation of nanoparticles, and a maximum turnover number of 1340 and a turnover frequency above 10000 for the combination of a Pt-complex as a catalyst and [Ru(bpy)3]2+ as a photosensitizer was achieved. Mechanistic studies revealed a reduced hydride dimer active for photocatalytic HER.

N -bridged bis-AMOX ligands are used as synthons for metallosupramolecular architectures.

An easily oxidizable Ru(II) complex, 2, of strongly σ-donating ligand has been synthesized, structurally characterized, and successfully used for the photocatalytic hydrogen evolution reaction (HER) as a photosensitizer (PS) under light irradiation of different wavelengths. This complex was found to be active for HER in combination with the classic [Co(dmgH)₂(py)Cl] as a catalyst with a TOF_max ranging from 8 (λ_irr = 630 nm) to 183 (λ_irr = 445 nm) mmol_H2·mol_PS^-1·min^-1 and TON_last ranging from 9 (λ_irr = 630 nm) to 349 (λ_irr = 445 nm) mol_H2·mol_PS^-1. The study presents the first example of photoproduction of H₂ using a Ru(II)-heteroleptic terpyridine PS with an oxidation potential below 0.6 V vs the SCE.

Testing 5 Cu( ii ) complexes (3× Cu; 2× Cu ₃ Tb) as CO ₂ RR catalysts under homogeneous photocatalytic conditions resulted in non-zero activity that could be incorrectly interpreted, so potential pitfalls are summarised to guide newcomers to the field.

We report herein the synthesis of a tridentate ligand (tris-4,4',4''-(4'''-pyridyl)-2,2':6',2''-terpyridine) and its corresponding homoleptic ruthenium(II) complex, which shows stable hydrogen photoproduction under red light (TON of 174 mol_H2·mol_PS ^-1 after 210 hours). A sustained activity under blue and green lights is also observed with TONs above 360 mol_H2·mol_PS ^-1 after 168 hours.

Effect of ancillary ligand with extended π surface on the photophysical properties and photocatalytic hydrogen production activity of bis(quinolinyl)isothiocyanate Pt( ii ) complexes were studied. The complexes were found to be sustainable for HER.

The title compound, C₁₉H₁₅BrN₂O, crystallizes with two similar molecules in the asymmetric unit. The extended structure features dimers linked by pairs of N—H...O and C—H...O hydrogen bonds. The HNCNO moiety of the title compound shows delocalization over the N—C—N part, as evidenced by the similar C—N bond distances.

Mononuclear complexes act as a first instance to evaluate the properties of metallo-polymers, as our results on mono- and ditopic terpyridine ligands suggest thus facilitating the development of metallo-supramolecular materials.

Pt(ii)-bis(quinolinyl) complexes were used for photocatalytic H₂ production with a TON of 1230 surpassing the performances of conventionally used Pt(ii)(terpyridyl) complexes.