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

Blaise Geoghegan, Wasinee Phonsri, Peter Horton, James Orton, Simon Coles, Keith S. Murray, Peter Cragg, Marcus Dymond, Ian Gass

Research output: Contribution to journalArticle

Abstract

The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC 4) and N,N-di(pyridin-2-yl)decanamide (LC 10) were combined with NCS - co-ligands to form the neutral heteroleptic Fe(ii) complexes trans-[Fe II(LC 4) 2(NCS) 2] (1C 4) and trans-[Fe II(LC 10) 2(NCS) 2] (1C 10). Variable temperature crystallographic studies revealed that 1C 4 is in the orthorhombic space group Pna2 1 between 85-200 K whereas 1C 10 is in the monoclinic space group P2 1/c between 85-140 K. The average Fe-N bond lengths suggest that at 85 K 1C 4 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. 1C 10 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 1C 4 undergoes semi-abrupt spin-crossover with T 1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C 10 undergoes an abrupt spin-crossover with T 1/2 = 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 T 1/2 value for thermal spin-crossover.

Original languageEnglish
Pages (from-to)17340-17348
Number of pages9
JournalDalton Transactions
Volume48
Issue number46
DOIs
Publication statusPublished - 15 Nov 2019

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Bond length
Ligands
Hysteresis
Magnetic susceptibility
Crystal lattices
Temperature
Hot Temperature

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Geoghegan, Blaise ; Phonsri, Wasinee ; Horton, Peter ; Orton, James ; Coles, Simon ; Murray, Keith S. ; Cragg, Peter ; Dymond, Marcus ; Gass, Ian. / Hysteretic thermal spin-crossover in heteroleptic Fe(II) complexes using alkyl chain substituted 2,2’-dipyridylamine ligands. In: Dalton Transactions. 2019 ; Vol. 48, No. 46. pp. 17340-17348.
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title = "Hysteretic thermal spin-crossover in heteroleptic Fe(II) complexes using alkyl chain substituted 2,2’-dipyridylamine ligands",
abstract = "The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC 4) and N,N-di(pyridin-2-yl)decanamide (LC 10) were combined with NCS - co-ligands to form the neutral heteroleptic Fe(ii) complexes trans-[Fe II(LC 4) 2(NCS) 2] (1C 4) and trans-[Fe II(LC 10) 2(NCS) 2] (1C 10). Variable temperature crystallographic studies revealed that 1C 4 is in the orthorhombic space group Pna2 1 between 85-200 K whereas 1C 10 is in the monoclinic space group P2 1/c between 85-140 K. The average Fe-N bond lengths suggest that at 85 K 1C 4 contains LS Fe(ii) centres; however, the ca. 0.18 {\AA} 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. 1C 10 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 {\AA}, which suggests a spin-transition to the HS state. Solid-state magnetic susceptibility measurements showed that 1C 4 undergoes semi-abrupt spin-crossover with T 1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C 10 undergoes an abrupt spin-crossover with T 1/2 = 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 T 1/2 value for thermal spin-crossover.",
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Hysteretic thermal spin-crossover in heteroleptic Fe(II) complexes using alkyl chain substituted 2,2’-dipyridylamine ligands. / Geoghegan, Blaise; Phonsri, Wasinee; Horton, Peter; Orton, James; Coles, Simon; Murray, Keith S.; Cragg, Peter; Dymond, Marcus; Gass, Ian.

In: Dalton Transactions, Vol. 48, No. 46, 15.11.2019, p. 17340-17348.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Hysteretic thermal spin-crossover in heteroleptic Fe(II) complexes using alkyl chain substituted 2,2’-dipyridylamine ligands

AU - Geoghegan, Blaise

AU - Phonsri, Wasinee

AU - Horton, Peter

AU - Orton, James

AU - Coles, Simon

AU - Murray, Keith S.

AU - Cragg, Peter

AU - Dymond, Marcus

AU - Gass, Ian

PY - 2019/11/15

Y1 - 2019/11/15

N2 - The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC 4) and N,N-di(pyridin-2-yl)decanamide (LC 10) were combined with NCS - co-ligands to form the neutral heteroleptic Fe(ii) complexes trans-[Fe II(LC 4) 2(NCS) 2] (1C 4) and trans-[Fe II(LC 10) 2(NCS) 2] (1C 10). Variable temperature crystallographic studies revealed that 1C 4 is in the orthorhombic space group Pna2 1 between 85-200 K whereas 1C 10 is in the monoclinic space group P2 1/c between 85-140 K. The average Fe-N bond lengths suggest that at 85 K 1C 4 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. 1C 10 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 1C 4 undergoes semi-abrupt spin-crossover with T 1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C 10 undergoes an abrupt spin-crossover with T 1/2 = 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 T 1/2 value for thermal spin-crossover.

AB - The alkyl chain carrying ligands N,N-di(pyridin-2-yl)butanamide (LC 4) and N,N-di(pyridin-2-yl)decanamide (LC 10) were combined with NCS - co-ligands to form the neutral heteroleptic Fe(ii) complexes trans-[Fe II(LC 4) 2(NCS) 2] (1C 4) and trans-[Fe II(LC 10) 2(NCS) 2] (1C 10). Variable temperature crystallographic studies revealed that 1C 4 is in the orthorhombic space group Pna2 1 between 85-200 K whereas 1C 10 is in the monoclinic space group P2 1/c between 85-140 K. The average Fe-N bond lengths suggest that at 85 K 1C 4 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. 1C 10 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 1C 4 undergoes semi-abrupt spin-crossover with T 1/2 = 127.5 K and a thermal hysteresis of ca. 13 K whereas, 1C 10 undergoes an abrupt spin-crossover with T 1/2 = 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 T 1/2 value for thermal spin-crossover.

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U2 - 10.1039/C9DT03412A

DO - 10.1039/C9DT03412A

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