Neal D. McDaniel

Polyoxometalate Embedding of a Tetraruthenium(IV)-oxo-core by Template-Directed Metalation of (γ-SiW10O36) 8- : A Totally Inorganic Oxygen-Evolving Catalyst

Solid state and solution evidence confirms the embedding of an adamantane-like, Ru4O6 fragment by the divacant, gamma-decatungstosilicate ligand. The resulting complex catalyzes water oxidation to oxygen with TON up to 500 and TOF > 450 h-1.

Fast Water Oxidation Using Iron

Photolysis of water, a long-studied strategy for storing solar energy, involves two half-reactions: the reduction of protons to dihydrogen and the oxidation of water to dioxygen. Proton reduction is well-understood, with catalysts achieving quantum yields of 34% when driven by visible light. Water oxidation, on the other hand, is much less advanced, typically involving expensive metal centers and rarely working in conjunction with a photochemically powered system. Before further progress can be made in the field of water splitting, significant developments in the catalysis of oxygen evolution are needed. Herein we present an iron-centered tetraamido macrocyclic ligand (Fe-TAML) that efficiently catalyzes the oxidative conversion of water to dioxygen. When the catalyst is combined in unbuffered solution with ceric ammonium nitrate, its turnover frequency exceeds 1.3 s(-1). Real-time UV-vis and oxygen monitoring of the active complex give insights into the reaction and decay kinetics.

Water Oxidation Catalyzed by Strong Carbene-Type Donor-Ligand Complexes of Iridium†

Title Water oxidation catalyzed by strong carbene-type donor ligand complexes of iridium Authors(s) Lalrempuia, Ralte; McDaniel, Neal Donald; Müller-Bunz, Helge; Bernhard, Stefan; Albrecht, Martin Publication date 2010-12 Publication information Angewandte Chemie International Edition, 49 (50): 9765-9768 Publisher Wiley Item record/more information http://hdl.handle.net/10197/3627 Publishers statement This is the authors version of the following article: Lalrempuia, R., McDaniel, N. D., Müller-Bunz, H., Bernhard, S. and Albrecht, M. (2010), Water Oxidation Catalyzed by Strong Carbene-Type Donor-Ligand Complexes of Iridium. Angew. Chem. Int. Ed., 49: þÿ 9 7 6 5 9 7 6 8 w h i c h h a s b e e n p u b l i s h e d i n f i n a l f o r m a t http://dx.doi.org/10.1002/anie.201005260 Publishers version (DOI) 10.1002/anie.201005260

Progress towards solar-powered homogeneous water photolysis

This highlight covers recent progress towards complete homogeneous water photolysis. Efforts in designing catalysts for water reduction, as well as their interaction with light harvesting complexes, are discussed. There are several successful catalyst archetypes for water oxidation that are reviewed herein; however, light driven oxygen evolution remains an area of limited success.

Solar fuels: thermodynamics, candidates, tactics, and figures of merit

Inorganic chemistry has been and continues to be a central discipline in the field of renewable energy and solar fuels. A fundamental approach to storing solar energy is artificial photosynthesis, whereby uphill chemical reactions are driven by light, e.g. the water gas shift reaction, halogen acid splitting, or water splitting. This article endeavors to define a common context for these research topics, particularly by analyzing the thermodynamic boundaries of photosynthesis. Specifically, the generalized efficiency restrictions on both light absorption and energy storage are expounded, the analogous limitations for several individual photosynthetic strategies are stated, several synthetic catalyst architectures are highlighted, the advantages of molecular and macroscopic approaches are discussed, and key figures of merit are presented.

Carbene iridium complexes for efficient water oxidation: scope and mechanistic insights

Iridium complexes of Cp* and mesoionic carbene ligands were synthesized and evaluated as potential water oxidation catalysts using cerium(IV) ammonium nitrate as a chemical oxidant. Performance was evaluated by turnover frequency at 50% conversion and by absolute turnover number, and the most promising precatalysts were studied further. Molecular turnover frequencies varied from 190 to 451 per hour with a maximum turnover number of 38 000. While the rate of oxygen evolution depends linearly on iridium concentration, concurrent spectroscopic and manometric observations following stoichiometric oxidant additions suggest oxygen evolution is limited by two sequential first-order reactions. Under the applied conditions, the oxygen evolving species appears to be a well-defined and molecular species based on kinetic analyses, effects of careful ligand design, reproducibility, and the absence of persistent dynamic light scattering signals. Outside of these conditions, the complex mechanism is highly dependent on reaction conditions. While confident characterization of the catalytically active species is difficult, especially under high-turnover conditions, this work strongly suggests the primary active species under these conditions is a molecular species.

Laser direct write printing of sensitive and robust light emitting organic molecules

We examine the effects of three laser direct-write (LDW) printing techniques on 9-anthracenemethanol and tris(8-hydroxyquinoline)aluminum (Alq3) organic luminophores in order to link the differences in transfer mechanism to the resulting material properties. Degradation can occur where laser light and elevated temperatures are transferred to the molecules, such as those printed via matrix-assisted or thin metal absorptive layer LDW. In contrast, thick film polyimide absorbing layer techniques eliminate damage in these sensitive materials by shielding them from excessive heat and laser illumination.