Kulmaczewski, R. orcid.org/0000-0002-3855-4530 and Halcrow, M.A. orcid.org/0000-0001-7491-9034 (2023) Iron(II) complexes of 2,6-bis(imidazo[1,2‑a]pyridin-2-yl)pyridine and related ligands with annelated distal heterocyclic donors. Dalton Transactions, 52 (41). pp. 14928-14940. ISSN 1477-9226
Abstract
Following a published synthesis of 2,6-bis(imidazo[1,2-a]pyridin-2-yl)pyridine (L1), treatment of α,α′-dibromo-2,6-diacetylpyridine with 2 equiv. 2-aminopyrimidine or 2-aminoquinoline in refluxing acetonitrile respectively gives 2,6-bis(imidazo[1,2-a]pyrimidin-2-yl)pyridine (L2) and 2,6-bis(imidazo[1,2-a]quinolin-2-yl)pyridine (L3). Solvated crystals of [Fe(L1)2][BF4]2 (1[BF4]2) and [Fe(L2)2][BF4]2 (2[BF4]2) are mostly high-spin, although one solvate of 1[BF4]2 undergoes thermal spin-crossover on cooling. The iron coordination geometry is consistently distorted in crystals of 2[BF4]2 which may reflect the influence of intramolecular, inter-ligand N⋯π interactions on the molecular conformation. Only 1[thin space (1/6-em)]:[thin space (1/6-em)]1 Fe[thin space (1/6-em)]:[thin space (1/6-em)]L3 complexes were observed in solution, or isolated in the solid state; a crystal structure of [FeBr(py)2L3]Br·0.5H2O (py = pyridine) is presented. A solvate crystal structure of high-spin [Fe(L4)2][BF4]2 (L4 = 2,6-di{quinolin-2-yl}pyridine; 4[BF4]2) is also described, which exhibits a highly distorted six-coordinate geometry with a helical ligand conformation. The iron(II) complexes are high-spin in solution at room temperature, but 1[BF4]2 and 2[BF4]2 undergo thermal spin-crossover equilibria on cooling. All the compounds exhibit a ligand-based emission in solution at room temperature. Gas phase DFT calculations mostly reproduce the spin state properties of the complexes, but show small anomalies attributed to intramolecular, inter-ligand dispersion interactions in the sterically crowded molecules.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Royal Society of Chemistry 2023 Open Access Article. Published on 02 October 2023. Downloaded on 10/12/2023 3:44:51 PM. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. |
Dates: |
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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) |
Funding Information: | Funder Grant number EPSRC (Engineering and Physical Sciences Research Council) EP/K012568/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 04 Oct 2023 11:35 |
Last Modified: | 21 Jan 2025 15:06 |
Status: | Published |
Publisher: | Royal Society of Chemistry |
Identification Number: | 10.1039/d3dt02747c |
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Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:203838 |