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Kovacs D, Kocsi D, Wells JAL, Kiraev SR, Borbas KE. Electron transfer pathways in photoexcited lanthanide(iii) complexes of picolinate ligands. Dalton Trans 2021; 50:4244-4254. [PMID: 33688904 DOI: 10.1039/d1dt00616a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A series of luminescent lanthanide(iii) complexes consisting of 1,4,7-triazacyclononane frameworks and three secondary amide-linked carbostyril antennae were synthesised. The metal binding sites were augmented with two pyridylcarboxylate donors yielding octadentate ligands. The antennae carried methyl, methoxymethyl or trifluoromethyl substituents in their 4-positions, allowing for a range of excited state energies and antenna electronic properties. The 1H NMR spectra of the Eu(iii) complexes were found to be analogous to each other. Similar results were obtained in the solid-state by single-crystal X-ray crystallography, which showed the structures to have nine-coordinate metal ions with heavily distorted tricapped trigonal prismatic geometries. Steady-state and time-resolved luminescence spectroscopy showed that the antennae could sensitize both Tb(iii) and Eu(iii), however, quantum yields were lower than in other octadentate complexes lacking pyridylcarboxylate. Complexes with more electron-poor pyridines were less emissive even when equipped with the same antenna. The oxidation and reduction potentials of the antennae and the pyridinecarboxylates, respectively, were determined by cyclic voltammetry. The obtained values were consistent with electron transfer from the excited antenna to the pyridine providing a previously unexplored quenching pathway that could efficiently compete with energy transfer to the lanthanide. These results show the crucial impact that photophysically innocent ligand binding sites can have on lanthanide luminescence.
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Affiliation(s)
- Daniel Kovacs
- Department of Chemistry, Ångström Laboratory, Box 523, Uppsala University, 75120, Uppsala, Sweden.
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3
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Kunth M, Schröder L. Binding site exchange kinetics revealed through efficient spin-spin dephasing of hyperpolarized 129Xe. Chem Sci 2020; 12:158-169. [PMID: 34163587 PMCID: PMC8178811 DOI: 10.1039/d0sc04835f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Spin exchange between different chemical environments is an important observable for characterizing chemical exchange kinetics in various contexts, including protein folding, chelation chemistry, and host-guest interactions. Such spins experience effective spin-spin relaxation rate, R 2,eff, that typically shows a dispersive behavior which requires detailed analysis. Here, we describe a class of highly simplified R 2,eff behavior by relying on hyperpolarized 129Xe as a freely exchanging ligand reporter. It provides large chemical shift separations that yield reduced expressions of both the Swift-Connick and the Carver-Richards treatment of exchange-induced relaxation. Despite observing a diamagnetic system, R 2,eff is dominated by large Larmor frequency jumps and thus allows detection of otherwise inaccessible analyte concentrations with a single spin echo train (only 0.01% of the overall hyperpolarized spins need to be transiently bound to the molecule). The two Xe hosts cryptophane-A monoacid (CrA-ma) and cucurbit[6]uril (CB6) represent two exemplary families of container molecules (the latter one also serving as drug delivery vehicles) that act as highly efficient phase shifters for which we observed unprecedented exchange-induced relaxivity r 2 (up to 866 s-1 mM-1). By including methods of spatial encoding, multiple data points can be collected simultaneously to isolate the exchange contribution and determine the effective exchange rate in partially occupied binding sites with a single delivery of hyperpolarized nuclei. The relaxivity is directly related to the guest turnover in these systems and temperature-dependent measurements yield an activation energy of E A = 41 kJ mol-1 for Xe@CrA-ma from simple relaxometry analysis. The concept is transferable to many applications where Xe is known to exhibit large chemical shifts.
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Affiliation(s)
- Martin Kunth
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V. (FMP) Campus Berlin-Buch, Robert-Roessle-Str. 10 13125 Berlin Germany +49 30 94793 121
| | - Leif Schröder
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V. (FMP) Campus Berlin-Buch, Robert-Roessle-Str. 10 13125 Berlin Germany +49 30 94793 121
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Vázquez-Montelongo EA, Vázquez-Cervantes JE, Cisneros GA. Current Status of AMOEBA-IL: A Multipolar/Polarizable Force Field for Ionic Liquids. Int J Mol Sci 2020; 21:ijms21030697. [PMID: 31973103 PMCID: PMC7037047 DOI: 10.3390/ijms21030697] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/11/2020] [Accepted: 01/16/2020] [Indexed: 01/25/2023] Open
Abstract
Computational simulations of ionic liquid solutions have become a useful tool to investigate various physical, chemical and catalytic properties of systems involving these solvents. Classical molecular dynamics and hybrid quantum mechanical/molecular mechanical (QM/MM) calculations of IL systems have provided significant insights at the atomic level. Here, we present a review of the development and application of the multipolar and polarizable force field AMOEBA for ionic liquid systems, termed AMOEBA–IL. The parametrization approach for AMOEBA–IL relies on the reproduction of total quantum mechanical (QM) intermolecular interaction energies and QM energy decomposition analysis. This approach has been used to develop parameters for imidazolium– and pyrrolidinium–based ILs coupled with various inorganic anions. AMOEBA–IL has been used to investigate and predict the properties of a variety of systems including neat ILs and IL mixtures, water exchange reactions on lanthanide ions in IL mixtures, IL–based liquid–liquid extraction, and effects of ILs on an aniline protection reaction.
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Affiliation(s)
| | | | - G. Andrés Cisneros
- Department of Chemistry, University of North Texas, Denton, TX 76201, USA; (E.A.V.-M.); (J.E.V.-C.)
- Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, TX 76201, USA
- Correspondence:
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Tu YJ, Lin Z, Allen MJ, Cisneros GA. Molecular dynamics investigation of water-exchange reactions on lanthanide ions in water/1-ethyl-3-methylimidazolium trifluoromethylsufate ([EMIm][OTf]). J Chem Phys 2018; 148:024503. [PMID: 29331119 DOI: 10.1063/1.4997008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We report a kinetic study of the water exchange on lanthanide ions in water/[1-ethyl-3-methylimidazolium][trifluoromethylsufate] (water/[EMIm][OTf]). The results from 17O-NMR measurements show that the water-exchange rates in water/[EMIm][OTf] increase with decreasing size of the lanthanide ions. This trend for water-exchange is similar to the previously reported trend in water/1-ethyl-3-methylimidazolium ethyl sulfate (water/[EMIm][EtSO4]) but opposite to that in water. To gain atomic-level insight into these water-exchange reactions, molecular dynamics simulations for lanthanide ions in water/[EMIm][OTf] have been performed using the atomic-multipole-optimized-energetics-for-biomolecular-application polarizable force field. Our molecular dynamics simulations reproduce the experimental water-exchange rates in terms of the trend and provide possible explanations for the observed experimental behavior. The smaller lanthanide ions in water/[EMIm][OTf] undergo faster water exchange because the smaller lanthanide ions coordinate to the first shell [OTf]- anions more tightly, resulting in a stronger screening effect for the second-shell water. The screening effect weakens the interaction of the lanthanide ions with the second-shell water molecules, facilitating the dissociation of water from the second-shell and subsequent association of water molecules from the outer solvation shells.
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Affiliation(s)
- Yi-Jung Tu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - Zhijin Lin
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - Matthew J Allen
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - G Andrés Cisneros
- Department of Chemistry, University of North Texas, Denton, Texas 76201, USA
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Fieser ME, Ferrier MG, Su J, Batista E, Cary SK, Engle JW, Evans WJ, Lezama Pacheco JS, Kozimor SA, Olson AC, Ryan AJ, Stein BW, Wagner GL, Woen DH, Vitova T, Yang P. Evaluating the electronic structure of formal Ln II ions in Ln II(C 5H 4SiMe 3) 31- using XANES spectroscopy and DFT calculations. Chem Sci 2017; 8:6076-6091. [PMID: 28989638 PMCID: PMC5625586 DOI: 10.1039/c7sc00825b] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 06/05/2017] [Indexed: 12/15/2022] Open
Abstract
The isolation of [K(2.2.2-cryptand)][Ln(C5H4SiMe3)3], formally containing LnII, for all lanthanides (excluding Pm) was surprising given that +2 oxidation states are typically regarded as inaccessible for most 4f-elements. Herein, X-ray absorption near-edge spectroscopy (XANES), ground-state density functional theory (DFT), and transition dipole moment calculations are used to investigate the possibility that Ln(C5H4SiMe3)31- (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb and Lu) compounds represented molecular LnII complexes. Results from the ground-state DFT calculations were supported by additional calculations that utilized complete-active-space multi-configuration approach with second-order perturbation theoretical correction (CASPT2). Through comparisons with standards, Ln(C5H4SiMe3)31- (Ln = Sm, Tm, Yb, Lu, Y) are determined to contain 4f6 5d0 (SmII), 4f13 5d0 (TmII), 4f14 5d0 (YbII), 4f14 5d1 (LuII), and 4d1 (YII) electronic configurations. Additionally, our results suggest that Ln(C5H4SiMe3)31- (Ln = Pr, Nd, Gd, Tb, Dy, Ho, and Er) also contain LnII ions, but with 4f n 5d1 configurations (not 4f n+1 5d0). In these 4f n 5d1 complexes, the C3h-symmetric ligand environment provides a highly shielded 5d-orbital of a' symmetry that made the 4f n 5d1 electronic configurations lower in energy than the more typical 4f n+1 5d0 configuration.
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Affiliation(s)
| | | | - Jing Su
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
| | - Enrique Batista
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
| | - Samantha K Cary
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
| | - Jonathan W Engle
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
- University of Wisconsin , Madison , Wisconsin 53711 , USA
| | | | | | - Stosh A Kozimor
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
| | - Angela C Olson
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
| | - Austin J Ryan
- University of California , Irvine , CA 92697 , USA .
| | - Benjamin W Stein
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
| | - Gregory L Wagner
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
| | - David H Woen
- University of California , Irvine , CA 92697 , USA .
| | - Tonya Vitova
- Karlsruhe Institute of Technology , Institute for Nuclear Waste Disposal , P.O. Box 3640 , 76021 Karlsruhe , Germany
| | - Ping Yang
- Los Alamos National Laboratory , Los Alamos , NM 87545 , USA . ; ;
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Tu YJ, Allen MJ, Cisneros GA. Simulations of the water exchange dynamics of lanthanide ions in 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIm][EtSO4]) and water. Phys Chem Chem Phys 2016; 18:30323-30333. [DOI: 10.1039/c6cp04957e] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Molecular dynamics simulations have been carried out to explain the water-exchange rates of lanthanide ions in water and water/[EMIm][EtSO4] observed from 17O-NMR experiments. Our simulations are in agreement with experimental results with respect to water-exchange trends.
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Affiliation(s)
- Yi-Jung Tu
- Department of Chemistry
- Wayne State University
- Detroit
- USA
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