There is an ongoing drive to replace the most common transparent conductor, indium tin oxide (ITO), with a material that gives comparable performance, but can be coated from solution at speeds orders of magnitude faster than the sputtering processes used to deposit ITO. Metal nanowires are currently the only alternative to ITO that meets these requirements. This Progress Report summarizes recent advances toward understanding the relationship between the structure of metal nanowires, the electrical and optical properties of metal nanowires, and the properties of a network of metal nanowires. Using the structure-property relationship of metal nanowire networks as a roadmap, this Progress Report describes different synthetic strategies to produce metal nanowires with the desired properties. Practical aspects of processing metal nanowires into high-performance transparent conducting films are discussed, as well as the use of nanowire films in a variety of applications.

A self-assembly-formed triglycylglycine macrocyclic ligand (TGG(4-)) complex of Cu(II), [(TGG(4-))Cu(II)-OH(2)](2-), efficiently catalyzes water oxidation in a phosphate buffer at pH 11 at room temperature by a well-defined mechanism. In the mechanism, initial oxidation to Cu(III) is followed by further oxidation to a formal "Cu(IV)" with formation of a peroxide intermediate, which undergoes further oxidation to release oxygen and close the catalytic cycle. The catalyst exhibits high stability and activity toward water oxidation under these conditions with a high turnover frequency of 33 s(-1).

As the terminal step in photosystem II, and a potential half-reaction for artificial photosynthesis, water oxidation (2H 2 O → O 2 þ 4e − þ 4H þ ) is key, but it imposes a significant mechanistic challenge with requirements for both 4e − ∕4H þ loss and O-O bond formation. Significant progress in water oxidation catalysis has been achieved recently by use of single-site Ru metal complex catalysts such as ½RuðMebimpyÞðbpyÞðOH 2 Þ 2þ [Mebimpy ¼ 2,6-bisð1-methylbenzimidazol-2-ylÞpyridine; bpy ¼ 2,2 0 -bipyridine]. When oxidized from Ru II -OH 2 2þ to Ru V ¼ O 3þ , these complexes undergo O-O bond formation by O-atom attack on a H 2 O molecule, which is often the rate-limiting step. Microscopic details of O-O bond formation have been explored by quantum mechanical/molecular mechanical (QM/MM) simulations the results of which provide detailed insight into mechanism and a strategy for enhancing catalytic rates. It utilizes added bases as proton acceptors and concerted atom-proton transfer (APT) with O-atom transfer to the O atom of a water molecule in concert with proton transfer to the base (B). Base catalyzed APT reactivity in water oxidation is observed both in solution and on the surfaces of oxide electrodes derivatized by attached phosphonated metal complex catalysts. These results have important implications for catalytic, electrocatalytic, and photoelectrocatalytic water oxidation.water split | O-O coupling | base effect | isotope effect I n natural photosynthesis, and in many schemes for artificial photosynthesis, water oxidation (is a key reaction with requirements for both 4e − ∕4H þ loss and O -O bond formation. Significant progress in water oxidation catalysis has been achieved recently by using single-site molecular catalysts (1-8). This includes elucidation of a mechanism in Ce (IV) catalyzed water oxidation by ½RuðtpyÞðbpmÞðOH 2 Þ 2þ and ½RuðtpyÞðbpzÞðOH 2 Þ 2þ (tpy ¼ 2; 2 0 ∶6 0 ; 2 00 -terpyridine; bpm ¼ 2; 2 0 -bipyrimidine; bpz ¼ 2; 2 0 -bipyrazine), Scheme 1 (1). Although undergoing multiple turnovers unchanged, these catalysts are relatively slow with O-O bond formation, often the rate-limiting step. In Scheme 1, O-atom transfer from ½Ru V ðtpyÞðbpmÞðOÞ 3þ to H 2 O is rate limiting and occurs with kð0.1 M HNO 3 ; 25°CÞ ¼ 8.9 × 10 −3 s −1 (5). To put rate into perspective, in a practical solar energy conversion scheme, a turnover rate on the millisecond or submillisecond time scale is required to match or exceed the rate of solar insolation. Achieving rates of this magnitude poses a considerable challenge (9).A useful strategy for achieving faster rates in metal complex catalysts exists based on an interplay between mechanism and systematic synthetic modifications. Ligand variations can be used to modify redox potentials, increase driving force, and decrease barriers (6). Mechanistic insight can uncover previously undescribed reaction pathways. We report here the use of a previously unidentified pathway to achieve greatly enhanced rates of electrocatalytic water oxidation for the catalyst, ½RuðMebim...

A series of monomeric ruthenium polypyridyl complexes have been synthesized and characterized, and their performance as water oxidation catalysts has been evaluated. The diversity of ligand environments and how they influence rates and reaction thermodynamics create a platform for catalyst design with controllable reactivity based on ligand variations.