Robert Edward Gross (1905-1988): ligation of a patent ductus arteriosus and the birth of a specialty.

The early 20th century saw an explosion in surgical expertise. Specialties dedicated to delicate organs such as the heart and vulnerable populations, like children, were in their infancy. Dr. William E. Ladd, the father of pediatric surgery, founded the first dedicated department of pediatric surgery at Boston Children’s Hospital in 1910. At the time, attempts at cardiac surgery almost universally ended in death of the patient. The first successful surgical treatment of the cardiac valves would not occur for another 15 years, and the great vessels would remain out of reach for decades more. Dr. Robert E. Gross, the shy and humble heir to the greats of this epoch, would push these embryonic fields into the modern era and train a generation of surgeons to face countless new challenges (Fig. 1)

The Role of Electrode Catalyst Interactions in Enabling Efficient CO2 Reduction with Mo(bpy)(CO)(4) As Revealed by Vibrational Sum-Frequency Generation Spectroscopy

Group 6 metal carbonyl complexes ([M(bpy)(CO)4], M = Cr, Mo, W) are potentially promising CO2 reduction electrocatalysts. However, catalytic activity onsets at prohibitively negative potentials and is highly dependent on the nature of the working electrode. Here we report in situ vibrational SFG (VSFG) measurements of the electrocatalyst [Mo(bpy)(CO)4] at platinum and gold electrodes. The greatly improved onset potential for electrocatalytic CO2 reduction at gold electrodes is due to the formation of the catalytically active species [Mo(bpy)(CO)3]2– via a second pathway at more positive potentials, likely avoiding the need for the generation of [Mo(bpy)(CO)4]2–. VSFG studies demonstrate that the strength of the interaction between initially generated [Mo(bpy)(CO)4]•– and the electrode is critical in enabling the formation of the active catalyst via the low energy pathway. By careful control of electrode material, solvent and electrolyte salt, it should therefore be possible to attain levels of activity with group 6 complexes equivalent to their much more widely studied group 7 analogues

A water-soluble Manganese complex for selective electrocatalytic CO2 reduction to CO

Relatively few solution electrocatalysts for CO2 reduction in aqueous solutions are reported. However to be sustainable, electrocatalytic CO2 reduction is likely to be coupled to water oxidation in a complete device. Here we report a water-soluble Mn polypyridyl complex for the electrocatalytic reduction of CO2 to CO. This complex shows activity across a broad pH range and an excellent selectivity at pH 9 (3.8:1, CO:H2). Cyclic voltammetry indicates activity across a range of different electrode materials (Boron doped diamond, glassy carbon and Hg/Au amalgams)

Hydrophilic, hole-delocalizing ligand shell to promote charge transfer from colloidal CdSe quantum dots in water

Colloidal cadmium chalcogenide nanocrystals are usually stabilized in polar solvents by functionalizing the surface with a layer of hydrophilic ligands. While these ligands protect against aggregation, they also present a steric barrier that hinders surface access. In applications that require charge transfer to and from nanocrystals, colloidal stability and surface access for redox species are therefore difficult to reconcile. This work assesses the possibility of a more dynamic ligand shell that not only provides stability to nanocrystals but also promotes charge transfer without the need for ligand removal. We use transient absorption spectroscopy to study CdSe quantum dots functionalized with hydrophilic, hole-delocalizing dithiocarbamate ligands in water for the first time, and find that a conjugated ligand facilitates charge transfer to redox species in solutio

Directing the mechanism of CO2 reduction by a Mn catalyst through surface immobilization

Immobilization of a Mn polypyridyl CO2 reduction electrocatalyst on nanocrystalline TiO2 electrodes yields an active heterogeneous system and also significantly triggers a change in voltammetric and catalytic behaviour, relative to in solution. A combination of spectroelectrochemical techniques are presented here to elucidate the mechanism of the immobilised catalyst in-situ

Improving the efficiency of electrochemical CO2 reduction using immobilized manganese complexes

Immobilization of [Mn(bpy)(CO)3Br], (1) and [Mn(bpy(tBu)2)(CO)3Br] (2, where (bpy(tBu)2) = 4,4′-di-tert-butyl-2,2′-bipyridine) in Nafion/multi-walled carbon nanotubes (MWCNT) on glassy carbon yielded highly active electrodes for the reduction of CO2 to CO in aqueous solutions at pH 7. Films incorporating 2 have significantly improved selectivity towards CO2, with CO : H2 ∼ 1 at −1.4 V vs. SCE, exceeding that for the previously reported 1/MWCNT/Nafion electrode. Furthermore, we report the synthesis and subsequent electrochemical characterization of two new substituted Mn(i) bipyridine complexes, [Mn(bpy(COOH)2)(CO)3Br] (3) and [Mn(bpy(OH)2)(CO)3Br] (4) (where (bpy(COOH)2) = 4,4′-di-carboxy-2,2′-bipyridine and (bpy(OH)2) = 4,4′-di-hydroxy-2,2′-bipyridine). Both 3 and 4 were found to have some activity towards CO2 in acetonitrile solutions; however once immobilized in Nafion membranes CO2 reduction was found to not occur at significant levels.</p

Metal-organic conjugated microporous polymer containing a carbon dioxide reduction electrocatalyst

A metal-organic conjugated micorporous polymer (CMP) containing a manganese carbonyl electrocatalyst for CO2 reduction has been synthesised and electrochemically characterised. Incorporation in a rigid framework changes the behavior of the catalyst, preventing reductive dimerization. These initial studies demonstrate the feasibility of CMP electrodes that can provide both high local CO2 concentrations and well defined electrocatalytic sites

Manganese Carbonyl Complexes as Selective Electrocatalysts for CO2 Reduction in Water and Organic Solvents

[Image: see text] The electrochemical reduction of CO(2) provides a way to sustainably generate carbon-based fuels and feedstocks. Molecular CO(2) reduction electrocatalysts provide tunable reaction centers offering an approach to control the selectivity of catalysis. Manganese carbonyl complexes, based on [Mn(bpy)(CO)(3)Br] and its derivatives (bpy = 2,2′-bipyridine), are particularly interesting due to their ease of synthesis and the use of a first-row earth-abundant transition metal. [Mn(bpy)(CO)(3)Br] was first shown to be an active and selective catalyst for reducing CO(2) to CO in organic solvents in 2011. Since then, manganese carbonyl catalysts have been widely studied with numerous reports of their use as electrocatalysts and photocatalysts and studies of their mechanism. This class of Mn catalysts only shows CO(2) reduction activity with the addition of weak Brønsted acids. Perhaps surprisingly, early reports showed increased turnover frequencies as the acid strength is increased without a loss in selectivity toward CO evolution. It may have been expected that the competing hydrogen evolution reaction could have led to lower selectivity. Inspired by these works we began to explore if the catalyst would work in protic solvents, namely, water, and to explore the pH range over which it can operate. Here we describe the early studies from our laboratory that first demonstrated the use of manganese carbonyl complexes in water and then go on to discuss wider developments on the use of these catalysts in water, highlighting their potential as catalysts for use in aqueous CO(2) electrolyzers. Key to the excellent selectivity of these catalysts in the presence of Brønsted acids is a proton-assisted CO(2) binding mechanism, where for the acids widely studied, lower pK(a) values actually favor CO(2) binding over Mn–H formation, a precursor to H(2) evolution. Here we discuss the wider literature before focusing on our own contributions in validating this previously proposed mechanism through the use of vibrational sum frequency generation (VSFG) spectroelectrochemistry. This allowed us to study [Mn(bpy)(CO)(3)Br] while it is at, or near, the electrode surface, which provided a way to identify new catalytic intermediates and also confirm that proton-assisted CO(2) binding operates in both the “dimer” and primary (via [Mn(bpy)(CO)(3)](−)) pathways. Understanding the mechanism of how these highly selective catalysts operate is important as we propose that the Mn complexes will be valuable models to guide the development of new proton/acid tolerant CO(2) reduction catalysts

Controlling Visible Light-Driven Photoconductivity in Self-Assembled Perylene Bisimide Structures

Alanine-functionalized perylene bisimides (PBI-A) are promising photoconductive materials. PBI-A self-assembles at high concentrations (mM) into highly ordered wormlike structures that are suitable for charge transport. However, we previously reported that the photoconductive properties of dried films of PBI-A did not correlate with the electronic absorption spectra as activity was only observed under UV light. Using transient absorption spectroscopy, we now demonstrate that charge separation can occur within these PBI-A structures in water under visible light. The lack of charge separation in the films is shown by DFT calculations to be due to a large ion-pair energy in the dried samples which is due to both the low dielectric environment and the change in the site of hole-localization upon drying. However, visible light photoconductivity can be induced in dried PBI-A films through the addition of methanol vapor, a suitable electron donor. The extension of PBI-A film activity into the visible region demonstrates that this class of self-assembled PBI-A structures may be of use in a heterojunction system when coupled to a suitable electron donor