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Hysteretic thermal spin-crossover and symmetry breaking in heteroleptic Fe(II) complexes using alkyl chain substituted 2,2’-dipyridylamine ligands.

Hysteretic thermal spin-crossover and symmetry breaking in heteroleptic Fe(II) complexes using alkyl chain substituted 2,2’-dipyridylamine ligands.
Hysteretic thermal spin-crossover and symmetry breaking in heteroleptic Fe(II) complexes using alkyl chain substituted 2,2’-dipyridylamine ligands.
The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC4) and N,N-di(pyridin-2-yl)decanamide (LC10) were combined with NCS− co-ligands to form the neutral heteroleptic Fe(II) complexes trans-[FeII(LC4)2(NCS)2] (1C4) and trans-[FeII(LC10)2(NCS)2] (1C10). Variable temperature crystallographic studies revealed that 1C4 is in the orthorhombic space group Pna21 between 85–200 K whereas 1C10 is in the monoclinic space group P21/c between 85–140 K. The average Fe–N bond lengths suggest that at 85 K 1C4 contains LS Fe(II) centres; however, the ca. 0.18 Å increase in the average Fe–N bond lengths between 85 and 120 K suggests a spin-transition to the HS state occurs within this temperature interval. 1C10 contains LS Fe(II) centres between 85 and 105 K. Upon warming from 105 to 140 K the average Fe–N bond lengths increase by ca. 0.19 Å, which suggests a spin-transition to the HS state. Solid-state magnetic susceptibility measurements showed that 1C4 undergoes semi-abrupt spin-crossover with T1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C10 undergoes an abrupt spin-crossover with T1/2 = 119.0 K, and is also accompanied by thermal hysteresis of ca. 4 K. The crystallographic and magnetic data show that the length of the complex's alkyl chain substituents can have a large impact on the structure of the crystal lattice as well as a subtle effect on the T1/2 value for thermal spin-crossover.
0300-9246
17340-17348
Geoghegan, Blaise L.
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Phonsri, Wasinee
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Horton, Peter
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Orton, James
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Coles, Simon J.
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Murray, Keith S.
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Cragg, Peter J.
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Dymond, Marcus K
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Gass, Ian A.
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Geoghegan, Blaise L.
f92c23d3-84b2-4a37-b5c4-45887ae565a9
Phonsri, Wasinee
dfd62f21-6354-4404-982e-5eea2af651c5
Horton, Peter
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Orton, James
4e2a471f-9e11-4cb4-abb6-d0398047939f
Coles, Simon J.
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Murray, Keith S.
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Cragg, Peter J.
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Dymond, Marcus K
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Gass, Ian A.
426dea92-36c7-4c15-be57-22b4c1a19865

Geoghegan, Blaise L., Phonsri, Wasinee, Horton, Peter, Orton, James, Coles, Simon J., Murray, Keith S., Cragg, Peter J., Dymond, Marcus K and Gass, Ian A. (2019) Hysteretic thermal spin-crossover and symmetry breaking in heteroleptic Fe(II) complexes using alkyl chain substituted 2,2’-dipyridylamine ligands. Dalton Transactions, 48 (46), 17340-17348. (doi:10.1039/C9DT03412A).

Record type: Article

Abstract

The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC4) and N,N-di(pyridin-2-yl)decanamide (LC10) were combined with NCS− co-ligands to form the neutral heteroleptic Fe(II) complexes trans-[FeII(LC4)2(NCS)2] (1C4) and trans-[FeII(LC10)2(NCS)2] (1C10). Variable temperature crystallographic studies revealed that 1C4 is in the orthorhombic space group Pna21 between 85–200 K whereas 1C10 is in the monoclinic space group P21/c between 85–140 K. The average Fe–N bond lengths suggest that at 85 K 1C4 contains LS Fe(II) centres; however, the ca. 0.18 Å increase in the average Fe–N bond lengths between 85 and 120 K suggests a spin-transition to the HS state occurs within this temperature interval. 1C10 contains LS Fe(II) centres between 85 and 105 K. Upon warming from 105 to 140 K the average Fe–N bond lengths increase by ca. 0.19 Å, which suggests a spin-transition to the HS state. Solid-state magnetic susceptibility measurements showed that 1C4 undergoes semi-abrupt spin-crossover with T1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C10 undergoes an abrupt spin-crossover with T1/2 = 119.0 K, and is also accompanied by thermal hysteresis of ca. 4 K. The crystallographic and magnetic data show that the length of the complex's alkyl chain substituents can have a large impact on the structure of the crystal lattice as well as a subtle effect on the T1/2 value for thermal spin-crossover.

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Fe(dpa-Cn)2(NCS)2 SCO - Accepted Manuscript
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Accepted/In Press date: 10 November 2019
e-pub ahead of print date: 15 November 2019
Published date: 14 December 2019

Identifiers

Local EPrints ID: 436607
URI: http://eprints.soton.ac.uk/id/eprint/436607
ISSN: 0300-9246
PURE UUID: 64d4fd9e-a31a-4d26-b11a-98b29592c6a8
ORCID for Peter Horton: ORCID iD orcid.org/0000-0001-8886-2016
ORCID for Simon J. Coles: ORCID iD orcid.org/0000-0001-8414-9272

Catalogue record

Date deposited: 18 Dec 2019 17:30
Last modified: 26 Nov 2021 05:54

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Contributors

Author: Blaise L. Geoghegan
Author: Wasinee Phonsri
Author: Peter Horton ORCID iD
Author: James Orton
Author: Simon J. Coles ORCID iD
Author: Keith S. Murray
Author: Peter J. Cragg
Author: Marcus K Dymond
Author: Ian A. Gass

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