Oana Luca

University of Colorado Boulder | CUB · Department of Chemistry and Biochemistry

Electroanalytical methods have become central tools for the development of molecular redox chemistry in the context of energy sciences and synthetic methods. Cyclic voltammetry (CV) is a routine diagnostic method for the measurement of the equilibrium potential of a redox couple. When electrochemical processes are reversible, CV may be used to dete...

The present review covers organic transformations involved in the reduction of CO2 to chemical fuels. In particular, we focus on reactions of CO 2 with organic molecules to yield carboxylic acid derivatives as a first step in CO 2 reduction reaction sequences. These biomimetic initial steps create opportunities for tandem electrochemical/chemical r...

An electrochemical cell coupled with a recycle loop through a transmission FTIR cell is employed in studies of two free radical organic reactions, the oxidation of allylic alcohols and the trifluoromethylation of heteroarenes. Rapid mixing through the recycle loop allows continuous monitoring of reaction progress. Electrochemical generation of free...

This work reports the selective electrochemical conversion of CO2 to methane, the reverse reaction of fossil fuel combustion. This reaction is facilitated by preactivation of the CO2 molecule with an N-heterocyclic carbene (NHC) to form a zwitterionic species in the first step. In the presence of Ni(cyclam)2+ and CF3CH2OH, this species is shown to...

Aspects of the electrochemical reduction of nitrogen and carbon dioxide at molecular and heterogeneous catalysts are discussed. We focus on recent advances in the field and discuss some of the remaining challenges in the production of solar fuels from N2 and CO2 with a direct, integrated solar fuel device. We propose metrics of catalyst assessment...

Electrification to reduce or eliminate greenhouse gas emissions is essential to mitigate climate change. However, a substantial portion of our manufacturing and transportation infrastructure will be difficult to electrify and/or will continue to use carbon as a key component, including areas in aviation, heavy-duty and marine transportation, and th...

2,2’-Bis(4-dimethylaminophenyl)- and 2,2'-dicyclohexyl-1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[ d ]imidazole ((N-DMBI) 2 and (Cyc-DMBI) 2 ) are quite strong reductants with effective potentials of ca. −2 V vs ferrocenium/ferrocene, yet are relatively stable to air due to the coupling of redox and bond-breaking processes. Here, we ex...

The shift toward renewable energy generation sources, characterized by their non‐carbon emitting but variable nature, has spurred significant innovation in energy storage technologies. Advancements in foundational understanding from investments in basic science and clever engineering solutions, coupled with increasing industrial adoption, have resu...

Herein, we report a method to estimate the thermodynamic potentials of electrochemical reactions at different temperatures. We use a two-term Taylor series approximation of thermodynamic potential as a function of temperature, and we calculate the temperature sensitivity for a family of twenty seven known half reactions. We further analyze pairs of...

We use quinone reduction potentials to showcase molecularly tunable CO 2 binding strengths for a family of electrochemically generated quinoid molecular sorbents. In our study, we find that CO 2 binding stoichiometry varies with CO 2 concentration.

The review discusses recent advances in electrocatalytic radical coupling reactions involving carbon-centered radical species.

This work maps the thermodynamics of electrochemically generated C-nucleophiles for reactive capture of CO2. We do so by identifying a linear relationship between the pKa, the reduction potential of a protonated nucleophile and the nucleophile’s free energy of CO2 binding (ΔGbind). Through synergistic experiments and computations, this study establ...

An increased interest in the capture and conversion of carbon dioxide into valuable chemical products is fueled by impending societal and ecological consequences of increasing CO2 concentration in the atmosphere. This work utilizes Lackner's thermodynamic calculations for the capture of carbon dioxide from the atmosphere based on a single sorbent a...

The present review describes electrochemical methods for the recovery of chemical feedstocks from waste materials. We emphasize the use of electrical current, fields, and controlled potentials as sustainable, scalable solutions to impending societal challenges such as materials recycling and the management of solid wastes. This review focuses on tw...

This article covers the organometallic chemistry of Group 7 with pincer and noninnocent ligands since 2005. The synthesis and reactivity of manganese, rhenium and technetium complexes is described, as well as their representative catalytic applications.

The decrease of total amount of atmospheric CO2 is an important societal challenge in which CO2 reduction has an important role to play. Electrocatalytic CO2 reduction with homogeneous catalysts is based on highly tunable catalyst design and exploits an abundant C1 source to make valuable products such as fuels and fuel precursors. These methods ca...

This work describes new methods for the chemical recycling of end-use poly(ethylene terephthalate) (PET) in batch, microwave and electrochemical reactors. The reactions are based on basic hydrolysis of the ester moieties in the polymer framework and occur under mild reaction conditions with low-cost reagents. We report end-use PET depolymerization...

This work examines the relative reactivities of ReI and MnI tricarbonyl pyridine-2,6-bis-N-heterocyclic carbene pincers M(CO)3CNCBnX (M = Re, Mn and X = Cl and Br) towards catalysis for the electrochemical conversion of CO2 to CO. Unlike prior well-studied group VII catalysts, Mn(CO)3CNCBnX is extraordinarily active, while the new Re(CO)3CNCBnX com...

This work studies the electrocatalytic disproportionation of CO2 into CO and CO32– mediated by a [Mn-2,6-bis(1-(alkyl)imidazol-2-ylidene)pyridine]Br pincer complex. We identify three mechanistic scenarios involving one or two catalytically active metal centers in the activation of carbon dioxide and use density functional theory to map out the ener...

This work reports the first example of mono-nuclear Cu pincers with SNS ligation acting as electrocatalyst precursors for the electrochemical conversion of carbon dioxide to CO and H2 in protic organic media.

We report the synthesis, characterization, and catalytic CO2 reduction activity of two LMn(CO)3Br complexes with carbene-pyridine-carbene pincer ligands, [MnCNCMe]Br 1 and [MnCNCBn]Br (Bn = benzyl) 2. X-ray crystallography reveals an octahedral coordination environment with an outer sphere Br anion for 1. Catalyst 2 performs the reduction of CO2 to...

The present review surveys current chemical understanding of catalysis by addition and removal of an electron. As an overarching theme of this type of catalysis, we introduce the role of redox scales in oxidation and reduction reactions as a direct analogue of pK a scales in acid/base catalysis. Each scale is helpful in determining the type of reac...

We report that the thermal decomposition of formic acid to CO may occur under electrochemically-relevant conditions by mild heating. These thermal effects may play a role in the outcome of electrolytic experiments as an artifact of resistive, local heating and illumination. This non-Faradaic reactivity pathway may therefore need consideration in th...

Teachers of introductory chemistry face the reality of outdated curricula and decreased student interest. The retention rates of students in the sciences remain troubling and the need to revisit course content and teaching methods has become increasingly apparent. A more general course framework developed on the principles of scientific teaching an...

We outline the teaching framework, goals, objectives and assessment addressing diversity for a unit on chemical equilibrium in a synergistic introductory course in chemistry and physics.

Intermittent renewable energy technol. require scalable developments to allow them to compete with fossil fuels. As such, the solar-driven prodn. of chem. fuels from an untapped carbon source such as carbon dioxide (CO_2) remains a key challenge. In order to develop such a technol., the selective electrochem. CO_2 conversion to fuels with low appli...

The electronic and magnetic properties of the complexes [Co(terpy)Cl2 ] (1), [Co(terpy)(NCS)2 ] (2), and [Co(terpy)2 ](NCS)2 (3) were investigated. The coordination environment around Co(II) in 1 and 2 leads to a high-spin complex at low temperature and single-molecule magnet properties with multiple relaxation pathways. Changing the ligand field a...

A tridentate NNN Ni(II) complex, shown to be an electrocatalyst for aqueous H2 production at low overpotentials, is studied by using temperature-dependent paramagnetic (1)H NMR. The NMR T1 relaxation rates, temperature dependence of the chemical shifts, and dc SQUID magnetic susceptibility are correlated to DFT chemical shifts and compared with the...

We now report the electrocatalytic dehydrogenation of tetrahydroquinaldine by an electron-rich CpNi N-heterocyclic carbene (NHC) with quinoid ligand motifs and explore the effects of quinone additives on CpNi compounds without quinoid NHC ligands. Our CpNi(NHC) catalyst exhibits dehydrogenative electrocatalytic activity and demonstrates that a mole...

A series of CpNi(NHC) halide complexes are synthesized from Cp2Ni and the azolium halide. Their X-ray structures and electrochemistry are reported.

Our research effort is directed towards the development of basic science that lays the foundation for enabling a next generation of fuel cell systems for mobile and stationary applications based on the recyclable use of high energy density liquid organic fuels. In the context of a proposed hydrogen economy and current drive for greener, sustainable...

Odd-electron, redox-active ligands are discussed in the context of catalysis. We focus on ligand-based, non-singlet state intermediates and their participation in catalytic processes and related stoichiometric transformations.

Nonplatinum metals are needed to perform cost-effective water reduction electrocatalysis to enable technological implementation of a proposed hydrogen economy. We describe electrocatalytic proton reduction and H(2) production by two organometallic nickel complexes with tridentate pincer ligands. The kinetics of H(2) production from voltammetry is c...

C-H activation of the methyl group of toluene and related ArCH 3 derivatives by 2,3-dichloro-4,5-dicyano-1,4-benzoquinone (DDQ) gives insertion products, ArCH 2O[C 6Cl 2(CN) 2]OH via a rate-determining hydride abstraction by DDQ. The resulting benzylic ether can undergo reactions with phosphines to give benzylic phosphonium salts (Wittig reagents)...

A NiII complex with a redox-active pincer ligand reduces protons at a low overpotential in aqueous acidic conditions. A combined experimental and computational study provides mechanistic insights into a putative catalytic cycle.

The structure and electrochemical properties of a series of bis(imino)pyridine Co(II) complexes (NNN)CoX(2) and [(NNN)(2)Co][PF(6)](2) (NNN = 2,6-bis[1-(4-R-phenylimino)ethyl]pyridine, with R = CN, CF(3), H, CH(3), OCH(3), N(CH(3))(2); NNN = 2,6-bis[1-(2,6-(iPr)(2)-phenylimino)ethyl]pyridine and X = Cl, Br) were studied using a combination of elect...

Reliable calculations of redox potentials could provide valuable insight into catalytic mechanisms of electrochemically active transition-metal complexes as well as guidelines for the design of new electrocatalysts. However, the correlation between theoretical and experimental data is often uncertain, since redox properties depend strongly on exper...

The process of redox catalysis has been known and well studied theoretically and experimentally for several decades. Studies of redox catalysis can be instrumental in determining mechanistic aspects of electrochemical reactions and in measuring basic thermodynamic and kinetic parameters. The application of redox catalysis to the electrochemical deh...

2,3-Dichloro-5,6-dicyanobenzoquinone (DDQ) is an electrochemical oxidationcatalyst for a secondary amine, a model system for virtual hydrogenstorage by removal of a hydrogen equivalent from an amine; a computational study provides mechanistic information.

This work explores methods for the synthesis of polyhedral oligomeric silsesquioxanes (POSS) and their use in the design of organic and metal-organic framework materials. Specifically, this work focuses on the octameric POSS (R8Si8O12) due to its unique cubic geometry, thermal stability, and multi-functionality. The Si8O12 cage in POSS offers a rig...