Editorial Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
pubs.acs.org/IC
Women in Inorganic Chemistry: Synthetic Chemistry Addressing Challenges in Energy and the Environment
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water solutions and in dry acetonitrile and dimethylformamide. In this work, they characterized the conversion of soluble cobalt species to electrode-adsorbed films, and the influences of these processes on electrocatalytic reactivity (acs.inorgchem.6b02586). Dempsey’s group also investigated a nickel hydride complex and its reactivity toward different acids and how the changes influence the compound’s ability to catalytically generate dihydrogen. These authors found that the nature of the chosen acid influences the reaction rate, not just its pKa, but also characteristics such as the acid’s tendency to homoconjugate, heterconjugate, or dimerize (acs.inorgchem.6b00885). Claudia Turro and Kim Dunbar are interested in the catalytic production of H2 from H+ as well. The authors investigated how the ligand scaffold between diamine-bridged RhII,III2 complexes can be used to modulate the charge density on both redox-active metal centers throughout the catalytic cycle, thereby helping to determine the electronic requirements of electrocatalytic H+ reduction (acs.inorgchem.5b01823). Smaranda Marinescu and co-workers report on a series of cobalt complexes that efficiently reduce CO2 to CO, electrocatalytically. The cobalt centers, which are supported by macrocyclic aminopyridine-type ligands that can be modified with pendant proton relays, modulate the overpotential for CO2 reduction. The work provides a new class of complexes capable of performing the CO2 to CO conversion reaction and promises new mechanistic insight that will enable optimization of this important solar fuel reaction (jacs.6b01980). Christine McKenzie and co-workers synthesized through bulk electrolysis a nonheme FeIV oxo complex toward the development of electrocatalytic water purification systems. They showed that the electrocatalytic decomposition of carboxylic acids and alcohols to CO2 occurs through a radical hydrogen-atom-abstraction mechanism for the process. The authors attribute the enhanced reactivity to the presence of a donor carboxylate in the ligand, a functional group that is commonly found in the active sites of nonheme iron enzymes involved in biooxidation reactions (acs.inorgchem.7b02208). Two new copper complexes were isolated by Jalila Simaan and co-workers as models for copper-containing enzymes. These authors investigated the reactivity and found that the complexes facilitate the enzymatic oxidative cleavage of unreactive polysaccharides, such as cellulose and chitin, into more reactive species, through hydroxylation of inert C−H bonds at a copper site (acs.inorgchem.6b02165). Melanie Sanford and her group are interested in developing new ligands that can promote aryl−fluoroalkyl (RF) coupling at PdII centers, because RF groups are common in a variety of pharmaceuticals and agrochemicals. In this work, they couple density functional theory calculations with experimental results from the study of (PtBu3)PdII(Ph)(RF) (RF = CF3 or CF2CF3)
growing world population has led to rapidly increasing demands for energy, which have placed a significant burden on the environment. Nonrenewable energy sources such as coal and petroleum result in increasing amounts of unwanted CO2 in the atmosphere; however, renewable and sustainable wind and solar energy as alternatives bring their own challenges in terms of a lack of effective energy storage. Chemists have long sought to mimic photosynthesis and to convert solar energy into useable fuels. Those efforts extend to mimicking naturally occurring enzymes and their ability to catalytically process chemical species in order to develop sustainable ways to convert unreactive and abundant starting materials into industrially valuable products. These approaches are also devoted to the development of new processes for environmental cleanup, for example, through the degradative oxidation of pollutants in the environment (Gray, H. B. Nat. Chem. 2009, 10.1038/nchem.141; Lewis, N. S.; Nocera, D. G. Proc. Natl. Acad. Sci. 2006, 10.1073/pnas.0603395103). Finally, there is an ongoing search for new materials with improved electronic conductivity and magnetic properties, with the goal of improving the energy efficiency in lighting and electronics applications (DuBois, D. L. Inorg. Chem. 2014, 10.1021/ ic4026969; Hagfeldt, A.; Grätzel, M. Acc. Chem. Res. 2000, 10.1021/ar980112j; Gutfleisch et al. Adv. Mater. 2011, 10.1002/adma.201002180). In summary, chemistry has always been central in human progress, and chemists are therefore at the forefront of developing solutions in our quest for new, sustainable energy sources, as well as remediating the environment. In this issue focused on recently published articles in Inorganic Chemistry and the Journal of the American Chemical Society, we highlight the work of research groups led by women investigators in a celebration of their contributions to excellent science. We are cognizant of the worldwide presence of many exceptional women scientists and engineers making important discoveries. Here, however, we focus on women authors predominantly from North America, as we profile speakers presenting at a session on this same topic, “Synthetic Chemistry Addressing Challenges in Energy and the Environment”, at the New Orleans National American Chemical Society Meeting held in Spring 2018. Notably, the scientists highlighted here represent a wide range of research efforts: from molecular systems to extended solids, from synthesis to measurements, and from homogeneous to heterogeneous systems. We summarize these developments in terms of the dimensionality of the materials described. The research highlighted represents well the incredible breadth of exciting work currently occurring in inorganic chemistry. Several of the groups highlighted are driving the development of catalysis and electrocatalysis for the generation of chemical fuels. Jillian Dempsey and co-workers focused on molecular electrocatalysts for solar dihydrogen evolution. These authors used an anionic bis(dithiolato) complex of earthabundant cobalt, known to evolve dihydrogen in acetonitrile/ © XXXX American Chemical Society
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DOI: 10.1021/acs.inorgchem.8b00532 Inorg. Chem. XXXX, XXX, XXX−XXX
Inorganic Chemistry
Editorial
to show that the α-fluoride elimination pathway, which limits the selectivity and efficiency of these transformations, can be avoided by moving from CF3 to CF2CF3 (jacs.7b05216). Jenny Yang and her group are interested in the role that proximal redox-inactive metal cations play in promoting the reactivity and tuning the redox activity of a variety of biological and synthetic transition-metal complexes. To probe whether or not the effects are inductive or electrostatic, they synthesized a series of CoII Schiff base complexes with crown functionalities containing alkali- or alkaline-earth-metal cations and investigated how CoII/I redox potentials for the dicationic compounds correlate with the ionic size and Lewis acidity of the alkaline metal (acs.inorgchem.6b03098). Joan Broderick and her team are also interested in the influence of proximal redox-inactive metal cations on the reactivity, prompted by the fact that the properties of the active site [4Fe−4S]+ with and without S-adenosyl-L-methionine (SAM) varied significantly between batches of samples. They observed that the pyruvate formate lyase activating enzyme (PFLAE, an SAM enzyme that installs a catalytically essential glycyl radical on pyruvate formate lyase) binds a catalytically essential monovalent cation at its active site (jacs.7b04883). In a complementary study, Alison Parkin and her group of collaborators show another interesting case in which the shift in the distal [Fe4 S4]2+/+ redox potential of the electron entry/exit site in Escherichia coli hydrogenase-1 has a significant effect on its activity toward H2 production. They analyzed how a HyaAR193L variant disrupts a proposed Arg−His cation−π interaction in the secondary coordination sphere of the distal iron−sulfur cluster and concluded that there may be a “molecular wire” that connects the outer surface of a protein to a “buried” active site (jacs.7b03611). In their efforts to contrast and compare the reactivity of heterobimetallic Ti−Co and Zr−Co complexes and their ability to activate small molecules, which can function as earthabundant catalysts to produce ammonia from dinitrogen, Christine Thomas and co-workers explored complexes with double and triple bonds between the metal centers and their reactivity toward hydrazine and dinitrogen (acs.inorgchem.5b01962). In their continued efforts toward the isolation of efficient earth-abundant catalysts, the same research group synthesized a new bidentate ligand based on an N-heterocyclic phosphenium cation with an appended chlorinated phosphine side arm. In situ reactivity studies led to the isolation of new nickel complexes with planar phosphine phosphorus atoms and short Ni−P bonds due to multiple bonding from P → N σ donation and Ni → P π backdonation (acs.inorgchem.5b01363). Although a common theme in the research that we have highlighted thus far is catalysis, there is also a significant effort in the broader inorganic community in understanding the fundamental structure and bonding of novel complexes. To expand the library of heterobimetallic complexes with unusual asymmetric electronic and/or magnetic properties to one-dimensional coordination polymers, Linda Doerrer and coworkers isolated new thiocyanato-bridged Pt−M complexes, namely, discrete molecular species, as well as ion-separated species and one-dimensional polymers, respectively. Solid-state and magnetic studies show significant Pt···Pt interactions in the one-dimensional polymer and a ferromagnetic interaction between the S = 3/2 CrIII centers (acs.inorgchem.6b01182). Codrina Popescu and her collaborators are interested in chemical spintronics. They report the spin-crossover (SCO)
behavior of an FeIII catecholate−nitronylnitroxide (CAT-NN) complex (1-NN) and assess the effects of different ligands, catecholate ligand versus a semiquinone, on the SCO behavior (acs.inorgchem.5b00298). Work by Amanda Morris and co-workers addresses the synthesis of new materials that might be suitable for the capture of CO2 from exhaust streams. They performed a thermodynamic study of CO2 and N2 binding to metal−organic framework (MOF) materials containing unsaturated ZnII coordination sites, as a function of the solvent associated with the MOF (ic503047y). Natalia Shustova’s research group is at the forefront of pushing MOFs toward more tunable electronic properties by modifying the metal nodes in these structures. Here they report advances on three types of bimetallic MOF systems: Mx−yM′y MOFs (replacement of M by M′ in metal nodes), MxM′y MOFs (node extension through M′ incorporation), and Mx(ligand−M′y) MOFs (coordination of M′ to the organic linker) and demonstrate that metal node engineering, as well as the presence of unsaturated metal sites, can be combined with tunable framework topology to affect the density of the electronic states near the Fermi edge (jacs.7b01125). Two manuscripts by Susan Kauzlarich and co-workers describe the chemistry of various Zintl phases useful for thermoelectric devices. In the first (ic5027398), Zintl silicon precursors are used for the synthesis of Si nanoparticles (NPs). The authors assessed the effect of varying the alkali-metal cation in the [Si4]4−- and [Si9]4−-containing Zintl phases on the NP size and optical properties. In the second manuscript (acs.inorgchem.6b01947), these authors describe the role of rare-earth (RE) metal sites on the thermal and electronic properties of RE11Cd6Sb12 solid solutions, by measuring their thermoelectric properties from 5 to 300 K. Gordana Dukovic and co-workers discussed the relationship between soluble (Ga1−xZnx)(N1−xOx) nanocrystals (NCs) and their excited-state dynamics over the time window of 10−13− 10−4 s and the origin of visible absorption in (Ga1−xZnx)(N1−xOx). These materials play an important role in solar fuel generation, and the availability of the new soluble Ga NC will enable further studies on excited-state dynamics and optimization of materials for solar fuel development (jacs.5b02077). Solar fuels are of particular importance in sustainability, and with the goal of developing materials capable of solar hydrogen gas evolution, Li-Zhu Wu and co-workers isolated new selfassembled systems in which cocatalyst Pt nanoparticles and quantum dots, either CdSe or CdSe/CdS, are physically separated but electronically joined by simple molecular polyacrylate. The authors investigated the role of the polyacrylate in mediating electron transfer and the resulting energy-transfer efficiency on dihydrogen production (jacs.6b12976). Emily Weiss’s group describes studies of the effects of substitution in the ligand shell of PbS quantum dots (QDs). Ligand shells of QDs are often a mixture of the ligands used during the synthesis, and the properties of the QDs depend strongly on the nature of these shells. It is difficult though to characterize the nature of this shell. In the work presented here, Weiss and her group demonstrate the use of photoinduced electron-transfer experiments to understand the structure, morphology, and properties of the organic shell on QDs (jacs.5b13077). B
DOI: 10.1021/acs.inorgchem.8b00532 Inorg. Chem. XXXX, XXX, XXX−XXX
Inorganic Chemistry
Editorial
With the goal of understanding conductivity in extended solids, Hemamala Karunadasa and co-workers investigated the effects of applying pressures above the theoretical minimum required for suppressing Jahn−Teller distortion of the d9 Cu centers in a hybrid perovskite material. They report here the effects of pressure on the color and conductivity of these materials (ja512396m). Tanja Cuk and co-workers are interested in heterogeneous electrochemically or photoelectrochemically controlled catalysis. Here, they probed the fundamental processes governing the initial step of photocatalytic water oxidation on electrode surfaces and how the nature of the metal oxide/aqueous interface is determined by the intermediates formed by trapping photogenerated, valence-band holes on different reactive sites of the oxide surface (jacs.6b09550). Work by Linda Nazar and co-workers for lithium-ion batteries includes both theoretical and experimental probes of metal-ion substitution into olivine-type LiScSiO4 and LiInSiO4 structures. Here, the authors study mechanisms to enhance the charge capacity of the olivine-type battery materials through the replacement of PO43− anions with SiO44− to increase the alkalimetal content and, hence, electron transfer (acs.inorgchem.7b01453). The general theme of our virtual issue is clearly that fundamental inorganic chemistry is central to many of the key efforts in developing alternative energy solutions as well as to understanding how to control the reactivity, bonding, and physical properties of novel compounds. In celebrating the contributions of the women authors highlighted here, we applaud the significance, impact, and broad scope of their work, which is changing the way that we think about solving the most important energy problems that we face today.
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Ana de Bettencourt-Dias* Louise A. Berben Amy L. Prieto AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
Views expressed in this editorial are those of the authors and not necessarily the views of the ACS.
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DOI: 10.1021/acs.inorgchem.8b00532 Inorg. Chem. XXXX, XXX, XXX−XXX
