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Krückel T, Schauerte S, Ke J, Schlottmann M, Bausch S, Chen X, Räuber C, Almeida Silva ID, Wiegand T, Albrecht M. 7Li NMR Spectroscopy: A Tool for Determining Dimerization Constants and Averaged Dimerization Constants of the Monomer/Dimer Equilibrium of Hierarchical Helicates. Chemistry 2024; 30:e202400387. [PMID: 38451207 DOI: 10.1002/chem.202400387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/07/2024] [Accepted: 03/25/2024] [Indexed: 03/08/2024]
Abstract
7Li nuclear magnetic resonance (NMR) spectroscopy is an ideal tool to study hierarchically assembled helicates of the form Li[Li3L6Ti2]. Internally bound and external lithium ions can be well distinguished by solution- or solid-state NMR spectroscopy and dimerization constants of the monomer/dimer equilibrium can be easily determined in solution. Averaged dimerization constants can be estimated in case of statistical mixtures of helicates formed from mixtures of ligands.
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Affiliation(s)
- Tobias Krückel
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074, Aachen, Germany
| | - Steffen Schauerte
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074, Aachen, Germany
| | - Jinbo Ke
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074, Aachen, Germany
| | - Marcel Schlottmann
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074, Aachen, Germany
| | - Sandra Bausch
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074, Aachen, Germany
| | - Xiaofei Chen
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074, Aachen, Germany
| | - Christoph Räuber
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074, Aachen, Germany
| | | | - Thomas Wiegand
- Max-Planck Institut für chemische Energiekonversion, Stiftstr. 34-36, D-45470, Mülheim/Ruhr, Germany
- Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Worringerweg 2, D-52074, Aachen, Germany
| | - Markus Albrecht
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074, Aachen, Germany
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Albrecht M. The Monomer-Dimer Equilibrium of Triscatechol Titanium(IV)-Based Hierarchical Helicates as a Tool for the Development of Molecular Balances and Molecular Switches. Acc Chem Res 2023; 56:3271-3281. [PMID: 37955356 DOI: 10.1021/acs.accounts.3c00525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2023]
Abstract
ConspectusHierarchical helicates are formed by noncovalent connection of two or more monomeric metal complex units, e.g., by bridging metal cations. A unique kind of hierarchical helicate is obtained from 3-carbonyl substituted catechol ligands with titanium(IV) ions in the presence of lithium cations. This kind of supramolecular complex shows in solution a "monomer-dimer" equilibrium. There are different possibilities (solvent, countercation, substituents at carbonyl unit, etc.) to shift this equilibrium to either the monomer or the dimer side. Thus, the lithium-bridged catecholate-based hierarchical helicates resemble a molecular switch. In this Account, different aspects are discussed of how this unique behavior of the dimeric titanium catecholates can be used for application.Thorough investigation of the energetics of the monomer-dimer equilibrium leads to a deeper understanding of the thermodynamic and kinetic effects of the dimerization (or dissociation) process. In this context, even weak interaction of substituents in the periphery of the complexes can be observed. Hereby on the one hand, solvent effects have an important influence and can be easily evaluated. The thorough understanding of the behavior of the monomer-dimer equilibrium allows one to develop some novel applications. In this respect, the use of the hierarchical helicate-based switch as a platform for reaction control and catalysis is described. Decent enantioselectivities up to ee = 58% can be found in Diels-Alder reactions in the periphery of the dimers, while switching to the monomer as a reaction platform still allows the cycloaddition reaction but turns the selectivity off. Additionally, it is described that catalytically important units can be introduced and hydrogenation reactions as well as Michael-type reactions are catalyzed at the helicates.Covalent connection of two catechol ester units leads to classical helicates. Depending on the alkaline metal cation, those can be switched from a compressed to an expanded form or vice versa. Hereby the monomer-dimer equilibrium is transformed into a structural switch. The switching process can be initiated by removal or addition of lithium cations (e.g., by addition of [2.1.1]cryptand). Alternative switching possibilities are based in the case of glycol bridged helicates on cation translocation isomerism and with thioester derivatives it occurs spontaneously in DMSO. Introduction of chiral tethers results in a three state switch allowing expansion/compression as well as switching of the helicity.
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Affiliation(s)
- Markus Albrecht
- Institut für Organische Chemie, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany
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Scarpi-Luttenauer M, Mobian P, Barloy L. Synthesis, structure and functions of discrete titanium-based multinuclear architectures. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214439] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Fandos R, Rodríguez-Delgado A, Rodríguez A, Romero I, Organero JÁ, Álvarez E. Pathways to Metal–Ligand Cooperation in Quinoline-Based Titanium(IV) Pincers: Nonelectrophilic N-methylation, Deprotonation, and Dihydropyridine Formation. Organometallics 2021. [DOI: 10.1021/acs.organomet.1c00105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rosa Fandos
- Instituto de Nanociencia, Nanotecnología y Materiales Moleculares (INAMOL), Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Avda. Carlos III, s/n, 45071 Toledo, Spain
| | - Antonio Rodríguez-Delgado
- Instituto de Investigaciones Químicas, CSIC-Universidad de Sevilla, C/Américo Vespucio, 49, Isla de la Cartuja, 41092 Sevilla, Spain
| | - Ana Rodríguez
- ETS Ingenieros Industriales, Campus de Ciudad Real, Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 3, 13071 Ciudad Real, Spain
| | - Iván Romero
- Instituto de Nanociencia, Nanotecnología y Materiales Moleculares (INAMOL), Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Avda. Carlos III, s/n, 45071 Toledo, Spain
| | - Juan Ángel Organero
- Instituto de Nanociencia, Nanotecnología y Materiales Moleculares (INAMOL), Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Avda. Carlos III, s/n, 45071 Toledo, Spain
| | - Eleuterio Álvarez
- Instituto de Investigaciones Químicas, CSIC-Universidad de Sevilla, C/Américo Vespucio, 49, Isla de la Cartuja, 41092 Sevilla, Spain
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