Climate change is one of the greatest challenges facing humanity, and our continued sustainable development requires a portfolio of solutions to ultimately reduce the use of fossil fuels and decrease the concentration of carbon dioxide in our atmosphere. Chemistry is central to tackling this issue, and of the pathways to transform carbon dioxide into value-added compounds, single-step electrically driven chemical methods have attracted substantial interest in the last decade. This review places emphasis on the barriers that chemists must overcome to realize this technology and enable commercial use of electrochemical carbon dioxide reduction. We outline design strategies for gas-diffusion electrodes and electrolyzers that follow fundamental principles of catalysis to bridge the gap between catalyst discovery and integrated system engineering. These should address both technical (thermodynamic and kinetic) and practical (infrastructural) hurdles to implementation. We conclude by discussing how these approaches can be improved to help achieve a carbon-neutral economy.
The self-assembly of a series of dehydro[24]annulene derivatives into columnar stacks has been examined for its latent ability to form π-conjugated carbon-rich nanotubular structures through topochemical polymerizations. We have studied the parameters affecting self-assembly, including the nature of the substituent and crystallization conditions, using 10 different dehydro[24]annulene derivatives. In particular, hydrogen-bonding interactions through carbamate groups were found to be especially useful at directing the formation of nanotubular supramolecular assemblies. We have also evaluated the electronic coupling between neighboring dehydroannulene molecules within these supramolecular assemblies. Density functional calculations on the stacked supramolecular nanotube assemblies show that transfer integrals vary considerably between the three columnar assemblies, ranging from moderate to high (59-98 meV for the highest occupied molecular orbitals, 63-97 meV for the lowest unoccupied molecular orbitals), depending on the local molecular topology. In addition, the dehydro[24]annulene derivatives afforded distinct architectures in the crystal, including nanochannel arrays, sheets with solvent-filled pores, and lamellae. This work is an essential step toward a controlled formation of covalently linked carbon-rich nanostructures generated from molecular precursors with a latent diacetylene reactivity.
Tripyridylamine (TPA), a tetradentate ligand that forms 5-membered chelate rings upon metal coordination, has demonstrated significant utility in synthetic inorganic chemistry. An analogue with a phosphorus apical donor is a desirable target for tuning electronic structure and enhancing reactivity. However, this congener has been synthetically elusive. Prior attempts have resulted in tridentate coordination to transition metal ions due to a lack of ligand flexibility. Herein, we report the successful synthesis of tris(2-pyridylmethyl)proazaphosphatrane (TPAP), a more accommodating tripyridyl ligand containing an apical phosphorus donor. The TPAP ligand forms 6-membered chelate rings upon coordination and binds in the desired tetradentate fashion to a Co(II) ion. Structural studies elucidate the importance of ligand flexibility in tripodal ligands featuring phosphorus donors. Cyclic voltammetry, UV-vis, and solution magnetic susceptibility experiments of [Co(TPAP)(CH3CN)](2+) are also reported and compared to [Co(TPA)(CH3CN)](2+). Notably, magnetic susceptibility measurements of [Co(TPAP)(CH3CN)](2+) indicate a low spin electronic configuration, in contrast to [Co(TPA)(CH3CN)](2+), which is high spin.
We have studied the self-assembly behavior of dehydro[24]annulene (D24A) derivatives 1, 2a-2d, and 3a-3c at the liquid/solid interface using scanning tunneling microscopy (STM). Both the relative placement and the nature of the four D24A substituents strongly influence the self-assembly pattern. Overall, the eight D24A derivatives examined in this study display seven types of 2D packing patterns. The D24A derivatives 1, 2a, and 3a have either two or four stearate groups and adopt face-on configurations of their macrocyclic cores with respect to the highly oriented pyrolytic graphite (HOPG) surface. Their 2D packing pattern is determined by the interchain spacings and number of stearate substituents. The D24A derivatives 2b-2d and 3b-3c bear hydrogen-bonding carbamate groups to further strengthen intermolecular interactions. Face-on patterns were also observed for most of these compounds, while an unstable edge-on self-assembly was observed in the case of 2b at room temperature. Stable edge-on self-assemblies of D24A derivatives were sought for this work as an important stepping stone to achieving the on-surface topochemical polymerization of these carbon-rich macrocycles into tubular π-conjugated nanowires. The overall factors determining the 2D packing patterns of D24As at the liquid/solid interface are discussed on the basis of theoretical simulations, providing useful guidelines for controlling the self-assembly pattern of future D24A macrocycles.
Water oxidation is catalysed in Nature by a redox cofactor embedded in a hydrogen-bonded network designed to orchestrate proton transfer throughout the challenging 4 electron reaction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.