Shahid, N orcid.org/0000-0002-8090-7619, Burrows, KE, Pask, CM orcid.org/0000-0002-2241-5069 et al. (4 more authors) (2022) Heteroleptic Iron(II) Complexes of Chiral 2,6-Bis(oxazolin-2-yl)pyridine (PyBox) and 2,6-Bis(thiazolin-2-yl)pyridine Ligands ‒ the Interplay of Different Ligands on the Metal Ion Spin State. Dalton Transactions, 51 (11). pp. 4262-4274. ISSN 1477-9226
Abstract
Complexation of Fe[ClO4]2·6H2O by 1 equiv 2,6-bis((4S)-4-phenyl-4,5-dihydrooxazol-2-yl)pyridine ((S)-L1Ph) and 2,6-bis((4R)-4-phenyl-4,5-dihydrothiazol-2-yl)pyridine ((R)-L2Ph) cleanly affords [Fe((S)-L1Ph)((R)-L2Ph)][ClO4]2; [Fe((R)-L1iPr)((S)-L2iPr)][ClO4]2 (L1iPr = 2,6-bis(4-isopropyl-4,5-dihydrooxazol-2-yl)pyridine; L2iPr = 2,6-bis(4-isopropyl-4,5-dihydrothiazol-2-yl)pyridine) was prepared by a similar route. The compounds exhibit thermal spin-crossover in solution, at temperatures midway between the corresponding [Fe((R)-L1R)((S)-L1R)][ClO4]2 and [Fe((R)-L2R)((S)-L2R)][ClO4]2 (R = Ph or iPr) species. The spin states of [Fe(LR)(bimpy)][ClO4]2 and [Fe(LR)(bpp)][ClO4]2 (LR = L1R or L2R; bimpy = 2,6-bis(1H-benz-imidazol-2-yl)pyridine; bpp = 2,6-di(pyrazol-1-yl)pyridine) are also reported, with most examples exhibiting gradual spin-crossover in solution and the solid state. Although some products undergo partial ligand exchange in solution by 1H NMR, their solution T½ values appear unaffected by this and correlate well with their spin state energies from gas phase DFT calculations. The high-spin state of [Fe(L2R)(bpp)]2+ is more stabilised than expected, compared to the other [Fe(LR)L]2+ complexes studied (L = bimpy, bpp or terpy). That is explained by an interplay between the relative σ-basicities and π-acidities of the two ligands in each molecule. The steric influence of their phenyl or isopropyl ‘R’ substituents stabilises the heteroleptic complexes by up to 5 kcal mol‒1, compared to analogues lacking these groups.
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Copyright, Publisher and Additional Information: | This is protected by copyright. All rights reserved. This is an author produced version of an article published in Dalton Transactions. Uploaded in accordance with the publisher's self-archiving policy. | ||||||
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Institution: | The University of Leeds | ||||||
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Inorganic Chemistry (Leeds) The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Condensed Matter (Leeds) |
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Depositing User: | Symplectic Publications | ||||||
Date Deposited: | 24 Feb 2022 15:02 | ||||||
Last Modified: | 22 Feb 2023 01:13 | ||||||
Status: | Published | ||||||
Publisher: | Royal Society of Chemistry | ||||||
Identification Number: | https://doi.org/10.1039/D2DT00393G |
Commentary/Response Threads
- Shahid, N, Burrows, KE, Pask, CM, Cespedes, O, Howard, MJ, McGowan, PC and Halcrow, MA Heteroleptic Iron(II) Complexes of Chiral 2,6-Bis(oxazolin-2-yl)pyridine (PyBox) and 2,6-Bis(thiazolin-2-yl)pyridine Ligands ‒ the Interplay of Different Ligands on the Metal Ion Spin State. (deposited 24 Feb 2022 15:02) [Currently Displayed]