Effects of increasing ligand conjugation in Cu(I) photosensitizers on NiO semiconductor surfaces.

Dye-sensitized photoelectrodes may be used as heterogeneous components for fuel-forming reactions in photoelectrochemical cells. There has been increasing interest in developing Earth-abundant cheaper photosensitizers based on first-row transition metals. We describe here the synthesis, characterization, and study of the ground and excited state properties of three Cu(I) complexes bearing ligands with varying electron-accepting capacities and conjugation that may act as photosensitizers for wide bandgap semiconductors. Femtosecond transient absorption studies indicate that the nature of the final excited state is dictated by the extent of conjugation in the electron-accepting ligand, where shorter conjugation leads to the formation of a singly reduced ligand and longer conjugation leads to the formation of a ligand-centered final excited state. These complexes were surface anchored onto nanostructured NiO on conductive fluorine-doped tin oxide glass to fabricate photocathodes. It was found that even though the ligands with increasing conjugation have an effect on the formation of the final excited state in solution, all complexes exhibit similar photocurrents upon white light illumination, suggesting that charge transfer to NiO happens in advance of the formation of the final excited state.

A historical perspective on porphyrin-based metal-organic frameworks and their applications.

Porphyrins are important molecules widely found in nature in the form of enzyme active sites and visible light absorption units. Recent interest in using these functional molecules as building blocks for the construction of metal-organic frameworks (MOFs) have rapidly increased due to the ease in which the locations of, and the distances between, the porphyrin units can be controlled in these porous crystalline materials. Porphyrin-based MOFs with atomically precise structures provide an ideal platform for the investigation of their structure-function relationships in the solid state without compromising accessibility to the inherent properties of the porphyrin building blocks. This review will provide a historical overview of the development and applications of porphyrin-based MOFs from early studies focused on design and structures, to recent efforts on their utilization in biomimetic catalysis, photocatalysis, electrocatalysis, sensing, and biomedical applications.

Molecular Copper(I)-Copper(II) Photosensitizer-Catalyst Photoelectrode for Water Oxidation.

Copper(II)-based electrocatalysts for water oxidation in aqueous solution have been studied previously, but photodriving these systems still remains a challenge. In this work, a bis(diimine)copper(I)-based donor-chromophore-acceptor system is synthesized and applied as the light-harvesting component of a photoanode. This molecular assembly was integrated onto a zinc oxide nanowire surface, and upon photoexcitation, chronoamperometric studies reveal that the integrated triad can inject electrons directly into the conduction band of zinc oxide, generating oxidizing equivalents that are then transferred to a copper(II) water oxidation catalyst in aqueous solution, yielding O2 from water with a Faradaic efficiency of 76%.