Lanthanide Triflates Research Articles

(Invited) Innovation in Electrocatalysis: Magnetoelectrocatalysis

Electrochemical processes are less energy intensive than thermal processes, especially for inner sphere reactions such as HER (H2 evolution reaction), HOR (H2 oxidation reaction), OER (O2 evolution reaction), ORR (O2 reduction reaction), CO2RR (CO2 reduction reaction), and NH3 generation. Energetic costs and environmental burdens are lowered electrochemically, provided an appropriate electrocatalyst can be identified. Often, electrocatalysts are identified through edisonian surveys.Here, a more fundamental approach to identifying catalysts is posed as magnetoelectrocatalysis. Magnetic gradients drive electron transfer reactions across the electrode solution interface. This increases rates and efficiency, to lower energetic and environmental taxes. Demonstrated magnetoelectrocatalysis is presented for HER [1,2], ORR [3-5], and single carbon species electrochemistry including CO2RR [6].Fundamental approaches to identifying effective magnetoelectrocatalysts are presented.The financial support of the National Science Foundation (NSF CHE-1309366; CHE-0809745) and the Army Research Office (W911NF-19-1-0208 (74912-CH-II), DAAD19-02-1-0443, and several STTRs) are acknowledged. References Krysti L. Knoche Gupta, Heung Chan Lee, and Johna Leddy, “Magnetoelectrocatalysis: Evidence from the Hydrogen Evolution Reaction,” ACS Phys. Chem Au (2024), 4(2) 148–159, https://doi.org/10.1021/acsphyschemau.3c00039.Kasun S.R. Dadallagei, Daniel L. Parr IV, Joshua R. Coduto, Andrew Lazicki, Sidney DeBie, Christian D.Haas, and Johna Leddy, “New Perspectives from Classical Transition State Theory: The Hydrogen Evolution Reaction on Metal Electrodes,” Journal of the Electrochemical Society (2023) 170(8) 086508; https://doi.org/10.1149/1945-7111/acf246.Krysti L. Knoche Gupta, Nadeesha P. W. Rathuwadu, and Johna Leddy, Communication—Voltammetry of Lanthanide (III) Triflates Accessible in Acetonitrile at Nafion Modified Electrodes, Journal of the Electrochemical Society (2021) 168(6) 066511, https://iopscience.iop.org/article/10.1149/1945-7111/ac0649.J. Leddy and K. L. Knoche, “Lanthanide electrochemistry,” US Patent 10,196,749, February 2019, Assignee: Johna Leddy, https://patents.google.com/patent/US10196749.J. Leddy and K. L. Knoche, “Lanthanide electrochemistry,” US Patent 10,081,873, September 2018, Assignee: Johna Leddy, https://patents.google.com/patent/US10081873.J. Leddy and N. P. W. Rathuwadu, “Carbon dioxide reduction and carbon compound electrochemistry in the presence of lanthanides,” US Patent 10,774,430, September 2020, Assignee: Johna Leddy, https://patents.google.com/patent/US10774430.

One-Stone-for-Multiple-Birds Additive Strategy for Highly Efficient and Stable Carbon-Based Hole-Transport-Layer-Free CsPbI2Br Solar Cells.

During fabrication and operation of perovskite solar cells (PSCs), defects commonly arise within the crystals as well as at grain boundaries. However, conventional additive strategies typically only serve to mitigate the occurrence of a single defect and fail to significantly enhance device performance. Herein, carbon-based hole-transport-layer-free CsPbI2Br devices are focused on, one kind of important PSCs with more stable structure and an appropriate bandgap for a semitransparent solar cell or a top cell in a tandem configuration, and present a highly efficient one-stone-for-multiple-birds additive strategy based on lanthanide trifluoromethanesulfonates (Ln(OTF)3, Ln: neodymium (Nd), europium (Eu), dysprosium (Dy), thulium (Tm)). Density functional theory calculations reveal that the Ln3+ ions with a smaller radius can elevate defect formation energy for Pb and I vacancies within the crystals, while the presence of OTF- can effectively passivating uncoordinated Pb2+ at grain boundaries. In addition, Ln(OTF)3 addition increases the grain size and meanwhile reduces the surface roughness of the CsPbI2Br layers. All these positive contributions lead to a significant enhancement in power conversion efficiency (PCE) to 15.13% which is among the top PCEs reported for the corresponding solar cells, from 11.80% of the pristine device without Tm(OTF)3 addition, while notably boosting long-term stability and reducing current-voltage hysteresis.

Anode-Free Lithium-Sulfur Batteries with a Rare-Earth Triflate as a Dual-Function Electrolyte Additive.

Anode-free lithium-sulfur batteries feature a cell design with a fully lithiated cathode and a bare current collector as an anode to control the total amount of lithium in the cell. The lithium stripping and deposition are key factors in designing an anode-free full cell to realize a practical cell configuration. To realize effective anode protection and achieve a good performance of the anode-free full cell, manipulation of the electrolyte chemistry toward the modification of the solid-electrolyte interphase on the anode is considered a feasible approach. In this study, the use of neodymium triflate, Nd(OTf)3, as a dual-function electrolyte additive is demonstrated to promote homogeneous catalysis on the cathode conversion reactions and the anode stabilization. Nd(OTf)3 not only facilitates the conversion reaction by promoting the polysulfide adsorption but also effectively protects the lithium-metal anode and stabilizes the lithium stripping and deposition during cycling. With this electrolyte modification, both Li∥Li2S half cells and Ni∥Li2S anode-free full cells support a high areal capacity of 5.5-7.0 mA h cm-2 and maintain a high Coulombic efficiency of 94-95% during cycling.

Easy Access to Ultrahigh-Molecular Weight Poly(1,3-dioxolane) by Rare Earth Triflates

Easy Access to Ultrahigh-Molecular Weight Poly(1,3-dioxolane) by Rare Earth Triflates

Influence of metal on coordination geometry and solution dynamics in complexes of cis-ethylenebis(diphenylphosphine oxide) and Ln(OTf)3 (Ln = La, Sm, Lu) X-ray crystal structures and NMR titration studies

This paper describes the synthesis and characterization of complexes containing the relatively rigid bisphosphine oxide ligand cis-ethylenebis(diphenylphosphine oxide) with three lanthanide (Ln) triflate salts (Ln = La3+, Sm3+, Lu3+). The complexes were characterized in the solid state by IR and X-Ray crystallography and show bidentate binding of the ligand to each metal center. The complexes were also studied at various Ln-ligand stoichiometries in solutions of CDCl3 using 1H and 31P NMR. These studies revealed that for the complexes where Ln = La3+ and Sm3+ ligand exchange is fast on the 1H and 31P NMR time scales when there are less than four equivalents of ligand in solution but slows when more than four equivalents are present. For the solution studies of complexes with Lu3+, ligand exchange is fast on the 1H NMR but slow on the 31P NMR time scale for all Lu-ligand stoichiometries.

The use of lanthanide triflates in the preparation of poly(thiourethane) covalent adaptable networks

Covalent adaptable networks (CANs) are new polymeric materials with the mechanical properties of thermosets and the possibility of being recycled like thermoplastics. Poly(thiourethane) networks have demonstrated vitrimeric-like behavior at high temperatures due to the trans-thiocarbamoylation process, which Lewis acids and bases can accelerate. In this study, we report the use of lanthanide triflates (La, Sm, Dy, Er, and Yb) as Lewis acid catalysts, a greener alternative to other metallic catalysts as dibutyltin dilaurate (DBTDL) widely used in poly(urethane) and poly(thiourethane) networks. Moreover, they are not as reactive as DBTDL, and the curing mixture can be manipulated for a longer time at room temperature. As monomers, trimethylolpropane tris(3-mercapto propionate) (S3), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI) have been used. We have demonstrated that the materials prepared with lanthanum triflate present the lowest relaxation times than those prepared with other lanthanide triflates or DBTDL. Calorimetry (DSC) and infrared spectroscopy (FTIR) were applied to study the curing process. The materials obtained were fully characterized by thermogravimetric analysis (TGA) and thermomechanical tests (DMA).

Migratory allylic arylation of 1,n-enols enabled by nickel catalysis

Transition-metal-catalyzed allylic substitution reactions (Tsuji−Trost reactions) proceeding via a π-allyl metal intermediate have been demonstrated as a powerful tool in synthetic chemistry. Herein, we disclose an unprecedented π-allyl metal species migration, walking on the carbon chain involving 1,4-hydride shift as confirmed by deuterium labeling experiments. This migratory allylic arylation can be realized under dual catalysis of nickel and lanthanide triflate, a Lewis acid. Olefin migration has been observed to preferentially occur with the substrate of 1,n-enols (n ≥ 3). The robust nature of the allylic substitution strategy is reflected by a broad scope of substrates with the control of regio- and stereoselectivity. DFT studies suggest that π-allyl metal species migration consists of the sequential β-H elimination and migratory insertion, with diene not being allowed to release from the metal center before producing a new π-allyl nickel species.

Samarium(III) Triflate in Organic Synthesis: a Mild and Efficient Catalyst

AbstractLanthanides have shown great potential in the field of magnetic materials, telecommunications, hard‐disk drives, catalysis, medicine, agriculture, and more. Recently, lanthanide complexes have gained significant attention in cancer diagnosis and therapy because of the multifunctional chemical and magnetic activities of the lanthanide‐ion 4 f electronic configuration. Among lanthanides, samarium metal and its derivatives have been the subject of many applications in organic transformations. Various metal triflates such as Bi(OTf)3, Yb(OTf)3, In(OTf)3, Sc(OTf)3, Er(OTf)3, Ce(OTf)3, Sm(OTf)3, and others play a profound role in developing novel eco‐friendly protocols in organic synthesis with excellent efficiency and selectivity. Among lanthanide triflate, samarium(III) triflate has a remarkable contribution in synthesizing promising organic molecules as it has been shown to be moisture tolerant and a reusable Lewis catalyst under mild conditions. The present review aims to focus on different useful protocols using samarium(III) triflate as an efficient catalyst for the first time elegantly.

Spinolate Lanthanide Complexes for High Circularly Polarized Luminescence Metrics in the Visible and Near-Infrared.

Analogues of Shibasaki's complexes supported by enantiopure Spinol are synthesized and characterized. The tris(Spinol) LnIII complexes are generated either by ligand deprotonation followed by complexation with lanthanide triflate salts or by in situ deprotonation by Ln(N(SiMe3)2)3 salts in the presence of additional base. The resulting complexes are found to be luminescent and chiroptically active for both circular dichroism and circularly polarized luminescence (CPL), notably producing strong CPL with dissymmetry factors (glum) of up to 0.50, 0.53, and 0.53 for Sm, Tb, and Dy, respectively. The Sm complex is found to be CPL-active in the near-infrared (NIR) region at 980 nm, representing the first report of NIR CPL from Sm. Additionally, the Tb complex, due to efficient sensitization (Φ = 0.846 in tetrahydrofuran) coupled with strong dissymmetry factors, achieves a CPL brightness (BCPL) of 3760 M-1 cm-1, the highest reported for any CPL-active compound to date. These are rare examples of compounds that show simultaneous improvement of both CPL metrics (glum and BCPL). Solid-state structural analysis of the Spinolate complexes and comparisons to other CPL-active analogues of Shibasaki's complexes also suggest that nondistorted geometries should generate even stronger metrics.

Total synthesis of chaiyaphumines A-D: A case study comparing macrolactonization and macrolactamization approaches

A comparison of macrolactonization and macrolactamization approaches to the synthesis of the pentadepsipeptide chaiyaphumines is outlined. Fmoc-based solid-phase synthesis approaches were used for the synthesis of the requisite precursors. Attempted solution-phase macrolactonization of a seco-acid precursor using Yamaguchi, pivaloyl chloride, or MNBA activation did not give cyclized products. The use of an MNBA / lanthanide(III) triflate mediated macrolactonization protocol led to an isomeric macrocycle. However, the use of a solution-phase macrolactamization approach using EDC·HCl / HOBt was achieved without detectable epimerization. This strategy was successfully applied to the total synthesis of the antimalarial compound chaiyaphumine A, as well as the natural products chaiyaphumine B, C, and D, by using a late-stage acylation of the threonine amino group. An X-ray crystal structure analysis of synthetic chaiyaphumine D reveals the presence of a type II’ beta turn and a type IV4 beta turn motif embedded in the 16-membered depsipeptide ring. This study illustrates potential challenge associated with macrolactonization approaches to depsipeptides compared to macrolactamization.

Peroxide-Selective Reduction of O2 at Redox-Inactive Rare-Earth(III) Triflates Generates an Ambiphilic Peroxide.

Metal peroxides are key species involved in a range of critical biological and synthetic processes. Rare-earth (group III and the lanthanides; Sc, Y, La-Lu) peroxides have been implicated as reactive intermediates in catalysis; however, reactivity studies of isolated, structurally characterized rare-earth peroxides have been limited. Herein, we report the peroxide-selective (93-99% O22-) reduction of dioxygen (O2) at redox-inactive rare-earth triflates in methanol using a mild metallocene reductant, decamethylferrocene (Fc*). The first molecular praseodymium peroxide ([PrIII2(O22-)(18C6)2(EG)2][OTf]4; 18C6 = 18-crown-6, EG = ethylene glycol, -OTf = -O3SCF3; 2-Pr) was isolated and characterized by single-crystal X-ray diffraction, Raman spectroscopy, and NMR spectroscopy. 2-Pr displays high thermal stability (120 °C, 50 mTorr), is protonated by mild organic acids [pKa1(MeOH) = 5.09 ± 0.23], and engages in electrophilic (e.g., oxygen atom transfer) and nucleophilic (e.g., phosphate-ester cleavage) reactivity. Our mechanistic studies reveal that the rate of oxygen reduction is dictated by metal-ion accessibility, rather than Lewis acidity, and suggest new opportunities for differentiated reactivity of redox-inactive metal ions by leveraging weak metal-ligand binding events preceding electron transfer.

Synthesis of poly(1,2-butylene oxide-stat-tetrahydrofuran) by controllable polymerization over Sc(OTf)3 for use in high-performance lubricating oil

Aliphatic polyethers are synthesized byring-opening polymerization (ROP) of the most common epoxide monomers, such as ethylene oxide (EO) and propylene oxide (PO). 1,2-Butylene oxide (BO) and tetrahydrofuran (THF) are potentially extended ROP monomers, which can give polyether unique properties. In this work, a series of poly(1,2-butylene oxide-stat-tetrahydrofuran)s (PBO-stat-PTHFs) with Mn of 900–3700 g·mol−1 were synthesized by cationic ring-opening polymerization (CROP) of BO with THF using strong Lewis acid Rare Earth triflates (RE(OTf)3) as catalysts and diols as an initiator at room temperature. PBO-stat-PTHFs product with yield up to 90 %, narrow polydispersity of Đ <1.30, and molar ratio of PBO to PTHF 1:1 were obtained. The copolymerization process was studied by in-situ IR and 1H NMR spectroscopy analysis, and the results showed that PBO-stat-PTHF is a statistical copolymer. The early stage of the polymerization reaction was dominated by the activated chain end mechanism (ACEM), which incorporates a large amount of THF into the polymer chains. However, the late stage of the polymerization reaction was dominated by the activated monomer mechanism (AMM), which incorporates a large amount of BO into the polymer chains. Most PBO-stat-PTHFs have a suitable Mn range, super high viscosity index (≥198) and low pour point (≤-53 °C), which can be used as a lubricant base oil and additives. In addition, PBO-stat-PTHFs have excellent miscibility with polyalphaolefin (PAO), which could significantly improve the PAO viscosity index. This study provides a mild route to construct high-performance copolyether materials through cationic ring-opening controllable polymerization.

Fluorescence-based measurement of the Lewis acidities of lanthanide triflates in solution

Despite the prominence of rare-earth complexes to act as Lewis acid catalysts in organic synthesis, the comprehensive measure of the Lewis acid strength of such compounds has yet to be performed due to incompatibilities with existing methods. We report our results in measurement of a sequence of lanthanide triflates via our recently established fluorescent Lewis adduct (FLA) method. The persistence in solution of these Lewis acids as solvated coordination complexes is accurately measurable by the FLA method. However, several of the rare-earth species exhibit fluorescence quenching, which may potentially inhibit the measurement. Nevertheless, meaningful FLA measurements were still possible, and the results correspond to both periodic trends and were even consistent with previous correlated reported data.

Catalytic conversion of waste corrugated cardboard into lactic acid using lanthanide triflates

The efficient strategy for waste conversion and resource recovery is of great interest in the sustainable bioeconomy context. This work reports on the catalytic upcycling of waste corrugated cardboard (WCC) into lactic acid using lanthanide triflates catalysts. WCC, a primary contributor to municipal solid wastes, has been viewed as a feedstock for producing a wide range of renewable products. Hydrothermal conversion of WCC was carried out in the presence of several lanthanide triflates. The reaction with erbium(III) triflate (Er(OTf)3) and ytterbium(III) triflate (Yb(OTf)3) resulted in high lactic acid yields, 65.5 and 64.3 mol%, respectively. In addition, various monomeric phenols were readily obtained as a co-product stream, opening up opportunities in waste management and resource recovery. Finally, technoeconomic analysis was conducted based on the experimental results, which suggests a significant economic benefit of chemocatalytic upcycling of WCC into lactic acid.

Cover Picture

The cover picture displays two different copolymerizations of ε‐caprolactone (CL) with 1,3‐dioxolane (DO) catalyzed by rare earth triflates. The panda represents Janus polymerization which yields multiblock copolymers of CL and DO, while the red panda represents cationic copolymerization which yields random copolymers. Janus polymerization combines anionic and cationic polymerizations on the two ends of a single propagating chain, followed by a self‐triggered polycondensation of anionic and cationic centers. The mechanism of copolymerization is determined by the element of rare earth in catalyst and the presence or absence of an epoxide initiator. More details are given in the article by Ling et al. on page 705—712. image

Janus Polymerization: A One‐Shot Approach towards Amphiphilic Multiblock Poly(ester‐acetal)s Directly from 1,3‐Dioxolane with ε‐Caprolactone

Comprehensive SummaryJanus polymerization consists of anionic and cationic ring opening polymerizations (AROP and CROP) at the two ends of a single propagating polymer chain, followed by a self‐triggered chain extension generating multiblock copolymers (MBCPs) in one step. In the contribution, Janus polymerization by Tm(OTf)3 or Er(OTf)3 catalyst with an epoxy initiator is applied to synthesize MBCPs of semi‐crystalline poly(ε‐caprolactone) (PCL) blocks from coordinated AROP and poly(1,3‐dioxolane‐co‐ε‐caprolactone) (P(DO‐co‐CL)) blocks from CROP of DO with CL. Meanwhile, amorphous random copolymers [P(DO‐r‐CL)] are synthesized as control by employing other rare earth triflates [RE(OTf)3, RE = Y, Nd, Gd and Lu] as catalysts or in the absence of an initiator via CROP. On account of the distinguishable chemical structures and thermal properties between Janus MBCPs and cationic random copolymers, Janus features are confirmed including the CROP and AROP at a single propagating chain. The resultant amphiphilic copolymers self‐assemble to nanoparticles in aqueous solution with designable diameters with the corresponding ratios of hydrophilic and hydrophobic segments. MBCPs exhibit good shape memory properties with appropriate deformation temperature close to human body's, providing a prospect on the applications in biomedical devices.

Hybrid poly-ether/carbonate ester electrolyte engineering enables high oxidative stability for quasi-solid-state lithium metal batteries

Building safe and high-energy-density lithium metal batteries (LMBs) is currently being pursued to sustain our modern lifestyles. However, new electrolyte engineering is rigorously required that is capable of simultaneously providing good protection on lithium metal anode and sustaining high oxidative stability at the cathode, besides sufficient bulk conductivity and low interfacial resistance. Here, we report a novel hybrid poly-ether/carbonate ester quasi-solid-state electrolyte with high oxidative stability formed by a simple and efficient in situ polymerization of strategy, in which ring-opening polymerization of ether-based 1,3-dioxolane (DOL) and ester-based ethylene carbonate (EC)-ethylmethyl carbonate (EMC) is initiated by rare-earth triflate catalyst Sc(OTf)3 at room temperature. Such electrolyte engineering not only achieves a sufficiently high ionic conductivity of 5 × 10−4 S cm−1 but enables a high anodic voltage limit of 5 V while maintaining feasible battery manufacture technology. The hybrid poly-DOL/EC/EMC quasi-solid-state electrolyte is capable of producing a stable solid electrolyte interphase (SEI) featuring Li plating/stripping over 500 h at 0.5 mA cm−2 and decreased charge transfer resistance. The derived Li||LiFePO4 quasi-solid-state LMB, benefited from the enhanced oxidative stability of electrolyte, exhibits a notable capacity of 169 mAh g−1 at 1C with no capacity decay after 300 cycles.

Communication—Voltammetry of Lanthanide (III) Triflates Accessible in Acetonitrile at Nafion Modified Electrodes

Lanthanides are common in catalysis and advanced technologies, but difficult to assess voltammetrically. Voltammetry for seven lanthanide(III) trifluoromethanesulfonate complexes Ln(OTf)3 is enabled at Nafion® modified platinum electrodes in acetonitrile. Voltammetric morphologies for La3+, Pr3+, Nd3+, Sm3+, Gd3+, Dy3+, and Yb3+ trifluoromethanesulfonate (triflate) complexes exhibit reduction waves between 0.2 to 0.1 V and −0.7 to −0.8 V vs NHE with coupled chemical processes.

The production of lactic acid from chemi-thermomechanical pulps using a chemo-catalytic approach

Previous work has shown that sulfonation and oxidation of chemi-thermomechanical pulps (CTMPs) significantly enhanced enzyme accessibility to cellulose while recovering the majority of carbohydrates in the water-insoluble component. In the work reported here, modified (sulfonated and oxidized) CTMPs derived from hard-and-softwoods were used to produce a DL-mix of lactic acid via a chemo-catalytic approach using lanthanide triflate (Ln (OTf)3) catalysts (Ln = La, Nd, Er, and Yb). It was apparent that sulfonation and oxidation of chemi-thermomechanical pulps (CTMPs) also enhanced Ln(OTf)3 catalyst accessibility to the carbohydrate components of the pulps, with the Er(OTf)3 catalysts resulting in significant lactic acid production. Under optimum conditions (250 °C, 60 min, 0.5 mmol catalyst g−1 biomass), 72% and 67% of the respective total carbohydrate present in the hard-and-softwood CTMPs could be converted to lactic acid compared to the respective 59% and 51% yields obtained after energy-intensive ball milling.

Synthesis of Well-defined Poly(tetrahydrofuran)-b-Poly(a-amino acid)s via Cationic Ring-opening Polymerization (ROP) of Tetrahydrofuran and Nucleophilic ROP of N-thiocarboxyanhydrides

The synthesis of block copolymers of poly(tetrahydrofuran)-b-poly(α-amino acid) (PTHF-b-PAA) is challenging since it is difficult to combine the two blocks produced via different/conflicting ring-opening polymerization (ROP) mechanisms. In this contribution, the cationic ROP of THF is catalyzed by rare-earth triflate [RE(OTf)3] and terminated by 2-(t-butyloxycarbonyl-amino) ethanol (BAE). After the deprotection of t-butyloxycarbonyl (Boc) group, the chain end of PTHF is quantitatively changed to amino group which thereafter initiates the nucleophilic ROP of α-amino acid N-thiocarboxyanhydrides (NTAs). Both polymerizations are well controlled, generating PTHF and PAA segments with designable molecular weights (MWs). PTHF-b-polylysine (PTHF-b-PLys) and PTHF-b-polysarcosine (PTHF-b-PSar) are obtained with MWs between 8.6 and 28.7 kg/mol. The above amphiphilic diblock copolymers form micelles in water. PTHF40-b-PSar32 acts as a surfactant to stabilize oil-in-water emulsions. Both segments of PTHF-b-PAA are biocompatible and promising in the biomedical application.