An iron ketimide single-molecule magnet [Fe4(NCPh2)6] with suppressed through-barrier relaxation

Andrew W. Cook; Joshua D. Bocarsly; Richard A. Lewis; Alexander J. Touchton; Simona Morochnik; Trevor W. Hayton

doi:10.1039/d0sc01578d

An iron ketimide single-molecule magnet [Fe₄(NCPh₂)₆] with suppressed through-barrier relaxation

Andrew W. Cook
, Joshua D. Bocarsly
, Richard A. Lewis
, Alexander J. Touchton
, Simona Morochnik
, Trevor W. Hayton

Research output: Contribution to journal › Article › peer-review

15 Scopus citations

Abstract

Reaction of FeBr₂ with 1.5 equiv. of LiNCPh₂ and 2 equiv. of Zn, in THF, results in the formation of the tetrametallic iron ketimide cluster [Fe₄(NCPh₂)₆] (1) in moderate yield. Formally, two Fe centers in 1 are Fe(i) and two are Fe(ii); however, Mössbauer spectroscopy and SQUID magnetometry suggests that the [Fe₄]⁶⁺ core of 1 exhibits complete valence electron delocalization, with a thermally-persistent spin ground state of S = 7. AC and DC SQUID magnetometry reveals the presence of slow magnetic relaxation in 1, indicative of single-molecule magnetic (SMM) behaviour with a relaxation barrier of U_eff = 29 cm^-1. Remarkably, very little quantum tunnelling or Raman relaxation is observed down to 1.8 K, which leads to an open hysteresis loop and long relaxation times (up to 34 s at 1.8 K and zero field and 440 s at 1.67 kOe). These results suggest that transition metal ketimide clusters represent a promising avenue to create long-lifetime single molecule magnets.

Original language	English
Pages (from-to)	4753-4757
Number of pages	5
Journal	Chemical Science
Volume	11
Issue number	18
DOIs	https://doi.org/10.1039/d0sc01578d
State	Published - 14 May 2020
Externally published	Yes

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@article{43f6836051f54915a5db673ba22875d1,

title = "An iron ketimide single-molecule magnet [Fe4(NCPh2)6] with suppressed through-barrier relaxation",

abstract = "Reaction of FeBr2 with 1.5 equiv. of LiNCPh2 and 2 equiv. of Zn, in THF, results in the formation of the tetrametallic iron ketimide cluster [Fe4(NCPh2)6] (1) in moderate yield. Formally, two Fe centers in 1 are Fe(i) and two are Fe(ii); however, M{\"o}ssbauer spectroscopy and SQUID magnetometry suggests that the [Fe4]6+ core of 1 exhibits complete valence electron delocalization, with a thermally-persistent spin ground state of S = 7. AC and DC SQUID magnetometry reveals the presence of slow magnetic relaxation in 1, indicative of single-molecule magnetic (SMM) behaviour with a relaxation barrier of Ueff = 29 cm-1. Remarkably, very little quantum tunnelling or Raman relaxation is observed down to 1.8 K, which leads to an open hysteresis loop and long relaxation times (up to 34 s at 1.8 K and zero field and 440 s at 1.67 kOe). These results suggest that transition metal ketimide clusters represent a promising avenue to create long-lifetime single molecule magnets.",

author = "Cook, \{Andrew W.\} and Bocarsly, \{Joshua D.\} and Lewis, \{Richard A.\} and Touchton, \{Alexander J.\} and Simona Morochnik and Hayton, \{Trevor W.\}",

note = "Publisher Copyright: This journal is {\textcopyright} The Royal Society of Chemistry.",

year = "2020",

month = may,

day = "14",

doi = "10.1039/d0sc01578d",

language = "English",

volume = "11",

pages = "4753--4757",

journal = "Chemical Science",

issn = "2041-6520",

publisher = "Royal Society of Chemistry",

number = "18",

}

TY - JOUR

T1 - An iron ketimide single-molecule magnet [Fe4(NCPh2)6] with suppressed through-barrier relaxation

AU - Cook, Andrew W.

AU - Bocarsly, Joshua D.

AU - Lewis, Richard A.

AU - Touchton, Alexander J.

AU - Morochnik, Simona

AU - Hayton, Trevor W.

PY - 2020/5/14

Y1 - 2020/5/14

N2 - Reaction of FeBr2 with 1.5 equiv. of LiNCPh2 and 2 equiv. of Zn, in THF, results in the formation of the tetrametallic iron ketimide cluster [Fe4(NCPh2)6] (1) in moderate yield. Formally, two Fe centers in 1 are Fe(i) and two are Fe(ii); however, Mössbauer spectroscopy and SQUID magnetometry suggests that the [Fe4]6+ core of 1 exhibits complete valence electron delocalization, with a thermally-persistent spin ground state of S = 7. AC and DC SQUID magnetometry reveals the presence of slow magnetic relaxation in 1, indicative of single-molecule magnetic (SMM) behaviour with a relaxation barrier of Ueff = 29 cm-1. Remarkably, very little quantum tunnelling or Raman relaxation is observed down to 1.8 K, which leads to an open hysteresis loop and long relaxation times (up to 34 s at 1.8 K and zero field and 440 s at 1.67 kOe). These results suggest that transition metal ketimide clusters represent a promising avenue to create long-lifetime single molecule magnets.

AB - Reaction of FeBr2 with 1.5 equiv. of LiNCPh2 and 2 equiv. of Zn, in THF, results in the formation of the tetrametallic iron ketimide cluster [Fe4(NCPh2)6] (1) in moderate yield. Formally, two Fe centers in 1 are Fe(i) and two are Fe(ii); however, Mössbauer spectroscopy and SQUID magnetometry suggests that the [Fe4]6+ core of 1 exhibits complete valence electron delocalization, with a thermally-persistent spin ground state of S = 7. AC and DC SQUID magnetometry reveals the presence of slow magnetic relaxation in 1, indicative of single-molecule magnetic (SMM) behaviour with a relaxation barrier of Ueff = 29 cm-1. Remarkably, very little quantum tunnelling or Raman relaxation is observed down to 1.8 K, which leads to an open hysteresis loop and long relaxation times (up to 34 s at 1.8 K and zero field and 440 s at 1.67 kOe). These results suggest that transition metal ketimide clusters represent a promising avenue to create long-lifetime single molecule magnets.

UR - https://www.scopus.com/pages/publications/85086234490

U2 - 10.1039/d0sc01578d

DO - 10.1039/d0sc01578d

M3 - Article

AN - SCOPUS:85086234490

SN - 2041-6520

VL - 11

SP - 4753

EP - 4757

JO - Chemical Science

JF - Chemical Science

IS - 18

ER -

An iron ketimide single-molecule magnet [Fe4(NCPh2)6] with suppressed through-barrier relaxation

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An iron ketimide single-molecule magnet [Fe₄(NCPh₂)₆] with suppressed through-barrier relaxation