Polymorphism in Fe[(p-IC₆H₄)B(3-Mepz)₃]₂ (pz = Pyrazolyl): Impact of Supramolecular Structure on an Iron(II) Electronic Spin-State Crossover

Daniel L. Reger; James R. Gardinier; Mark D. Smith; Ahmed M. Shahin; Gary J. Long; Leïla Rebbouh; Fernande Grandjean

doi:10.1021/ic048406q

Polymorphism in Fe[(p-IC₆H₄)B(3-Mepz)₃]₂ (pz = Pyrazolyl): Impact of Supramolecular Structure on an Iron(II) Electronic Spin-State Crossover

Daniel L. Reger
, James R. Gardinier
, Mark D. Smith
, Ahmed M. Shahin
, Gary J. Long
, Leïla Rebbouh
, Fernande Grandjean

Chemistry

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

Abstract

The new ligands Na[(p-IC ₆ H ₄ )B(3-Rpz) ₃ ] (R = H, Me) have been prepared by converting I ₂ C ₆ H ₄ to IC ₆ H ₄ SiMe ₃ with Li ^t Bu and SiMe ₃ Cl, and then to IC ₆ H ₄ BBr ₂ with BBr ₃ and subsequent reaction with 3 equiv of (un)substituted pyrazole and 1 equiv of NaO ^t Bu. These new ligands react with FeBr ₂ to give either purple, low-spin Fe[(p-IC ₆ H ₄ )B(pz) ₃ ] ₂ or colorless, high-spin Fe[(p-IC ₆ H ₄ )B(3-Mepz) ₃ ] ₂ . Depending upon the crystallization conditions, Fe[(p-IC ₆ H ₄ )B(3-Mepz) ₃ ] ₂ can exist both as two polymorphs and as a methylene chloride solvate. An examination of these polymorphs by variable-temperature X-ray crystallography, magnetic susceptibility, and Mössbauer spectroscopy has revealed different electronic spin-state crossover properties for each polymorph and yields insight into the influence of crystal packing, independent of other electronic perturbations, on the spin-state crossover. The first polymorph of Fe[(p-IC ₆ H ₄ )B-(3-Mepz) ₃ ] ₂ has a highly organized three-dimensional supramolecular structure and does not undergo a spin-state crossover upon cooling to 4 K. The second polymorph of Fe[(p-IC ₆ H ₄ )B(3-Mepz) ₃ ] ₂ has a stacked two-dimensional supramolecular structure, a structure that is clearly less well organized than that of the first polymorph, and undergoes an abrupt iron(II) spin-state crossover from high spin to low spin upon cooling below ca. 130 K. The crystal structure of the methylene chloride solvate of Fe[(p-IC ₆ H ₄ )B(3-Mepz) ₃ ] ₂ has a similar stacked two-dimensional supramolecular structure, but the crystals readily lose the solvate. The resulting desolvate undergoes a gradual spin-state crossover to the low-spin state upon cooling below ca. 235 K. It is clear from a comparison of the structures that the long-range solid-state organization of the molecules, which is controlled by noncovalent supramolecular interactions, has a strong impact upon the spin-state crossover, with the more highly organized structures having lower spin-crossover temperatures and more abrupt spin-crossover behavior.

Original language	American English
Journal	Inorganic Chemistry
Volume	44
DOIs	https://doi.org/10.1021/ic048406q
State	Published - Mar 1 2005

Keywords

Boron
Carbon
Dichloromethane
Hydrogen
Iron
Iron Derivative
Ligand
Poly(Pyrazolyl)borate Iron
Pyrazine Derivative
Pyrazolyl
Unclassified Drug
Chemical Reaction
Chemical Structure
Crystal Structure
Crystallization
Magnetism
Molecular Interaction
Mössbauer Spectroscopy
Nuclear Magnetic Resonance
Solid State
Synthesis
Temperature
X Ray Crystallography

Disciplines

Chemistry

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https://doi.org/10.1021/ic048406q

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@article{be7d696027804e1ea2c5d6d0e09e4373,

title = "Polymorphism in Fe[(p-IC₆H₄)B(3-Mepz)₃]₂ (pz = Pyrazolyl): Impact of Supramolecular Structure on an Iron(II) Electronic Spin-State Crossover",

abstract = " The new ligands Na[(p-IC 6 H 4 )B(3-Rpz) 3 ] (R = H, Me) have been prepared by converting I 2 C 6 H 4 to IC 6 H 4 SiMe 3 with Li t Bu and SiMe 3 Cl, and then to IC 6 H 4 BBr 2 with BBr 3 and subsequent reaction with 3 equiv of (un)substituted pyrazole and 1 equiv of NaO t Bu. These new ligands react with FeBr 2 to give either purple, low-spin Fe[(p-IC 6 H 4 )B(pz) 3 ] 2 or colorless, high-spin Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 . Depending upon the crystallization conditions, Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 can exist both as two polymorphs and as a methylene chloride solvate. An examination of these polymorphs by variable-temperature X-ray crystallography, magnetic susceptibility, and M{\"o}ssbauer spectroscopy has revealed different electronic spin-state crossover properties for each polymorph and yields insight into the influence of crystal packing, independent of other electronic perturbations, on the spin-state crossover. The first polymorph of Fe[(p-IC 6 H 4 )B-(3-Mepz) 3 ] 2 has a highly organized three-dimensional supramolecular structure and does not undergo a spin-state crossover upon cooling to 4 K. The second polymorph of Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 has a stacked two-dimensional supramolecular structure, a structure that is clearly less well organized than that of the first polymorph, and undergoes an abrupt iron(II) spin-state crossover from high spin to low spin upon cooling below ca. 130 K. The crystal structure of the methylene chloride solvate of Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 has a similar stacked two-dimensional supramolecular structure, but the crystals readily lose the solvate. The resulting desolvate undergoes a gradual spin-state crossover to the low-spin state upon cooling below ca. 235 K. It is clear from a comparison of the structures that the long-range solid-state organization of the molecules, which is controlled by noncovalent supramolecular interactions, has a strong impact upon the spin-state crossover, with the more highly organized structures having lower spin-crossover temperatures and more abrupt spin-crossover behavior.",

keywords = "Boron, Carbon, Dichloromethane, Hydrogen, Iron, Iron Derivative, Ligand, Poly(Pyrazolyl)borate Iron, Pyrazine Derivative, Pyrazolyl, Unclassified Drug, Chemical Reaction, Chemical Structure, Crystal Structure, Crystallization, Magnetism, Molecular Interaction, M{\"o}ssbauer Spectroscopy, Nuclear Magnetic Resonance, Solid State, Synthesis, Temperature, X Ray Crystallography",

author = "Reger, \{Daniel L.\} and Gardinier, \{James R.\} and Smith, \{Mark D.\} and Shahin, \{Ahmed M.\} and Long, \{Gary J.\} and Le{\"i}la Rebbouh and Fernande Grandjean",

year = "2005",

month = mar,

day = "1",

doi = "10.1021/ic048406q",

language = "American English",

volume = "44",

journal = "Inorganic Chemistry",

}

TY - JOUR

T1 - Polymorphism in Fe[(p-IC₆H₄)B(3-Mepz)₃]₂ (pz = Pyrazolyl): Impact of Supramolecular Structure on an Iron(II) Electronic Spin-State Crossover

AU - Reger, Daniel L.

AU - Gardinier, James R.

AU - Smith, Mark D.

AU - Shahin, Ahmed M.

AU - Long, Gary J.

AU - Rebbouh, Leïla

AU - Grandjean, Fernande

PY - 2005/3/1

Y1 - 2005/3/1

N2 - The new ligands Na[(p-IC 6 H 4 )B(3-Rpz) 3 ] (R = H, Me) have been prepared by converting I 2 C 6 H 4 to IC 6 H 4 SiMe 3 with Li t Bu and SiMe 3 Cl, and then to IC 6 H 4 BBr 2 with BBr 3 and subsequent reaction with 3 equiv of (un)substituted pyrazole and 1 equiv of NaO t Bu. These new ligands react with FeBr 2 to give either purple, low-spin Fe[(p-IC 6 H 4 )B(pz) 3 ] 2 or colorless, high-spin Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 . Depending upon the crystallization conditions, Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 can exist both as two polymorphs and as a methylene chloride solvate. An examination of these polymorphs by variable-temperature X-ray crystallography, magnetic susceptibility, and Mössbauer spectroscopy has revealed different electronic spin-state crossover properties for each polymorph and yields insight into the influence of crystal packing, independent of other electronic perturbations, on the spin-state crossover. The first polymorph of Fe[(p-IC 6 H 4 )B-(3-Mepz) 3 ] 2 has a highly organized three-dimensional supramolecular structure and does not undergo a spin-state crossover upon cooling to 4 K. The second polymorph of Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 has a stacked two-dimensional supramolecular structure, a structure that is clearly less well organized than that of the first polymorph, and undergoes an abrupt iron(II) spin-state crossover from high spin to low spin upon cooling below ca. 130 K. The crystal structure of the methylene chloride solvate of Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 has a similar stacked two-dimensional supramolecular structure, but the crystals readily lose the solvate. The resulting desolvate undergoes a gradual spin-state crossover to the low-spin state upon cooling below ca. 235 K. It is clear from a comparison of the structures that the long-range solid-state organization of the molecules, which is controlled by noncovalent supramolecular interactions, has a strong impact upon the spin-state crossover, with the more highly organized structures having lower spin-crossover temperatures and more abrupt spin-crossover behavior.

AB - The new ligands Na[(p-IC 6 H 4 )B(3-Rpz) 3 ] (R = H, Me) have been prepared by converting I 2 C 6 H 4 to IC 6 H 4 SiMe 3 with Li t Bu and SiMe 3 Cl, and then to IC 6 H 4 BBr 2 with BBr 3 and subsequent reaction with 3 equiv of (un)substituted pyrazole and 1 equiv of NaO t Bu. These new ligands react with FeBr 2 to give either purple, low-spin Fe[(p-IC 6 H 4 )B(pz) 3 ] 2 or colorless, high-spin Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 . Depending upon the crystallization conditions, Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 can exist both as two polymorphs and as a methylene chloride solvate. An examination of these polymorphs by variable-temperature X-ray crystallography, magnetic susceptibility, and Mössbauer spectroscopy has revealed different electronic spin-state crossover properties for each polymorph and yields insight into the influence of crystal packing, independent of other electronic perturbations, on the spin-state crossover. The first polymorph of Fe[(p-IC 6 H 4 )B-(3-Mepz) 3 ] 2 has a highly organized three-dimensional supramolecular structure and does not undergo a spin-state crossover upon cooling to 4 K. The second polymorph of Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 has a stacked two-dimensional supramolecular structure, a structure that is clearly less well organized than that of the first polymorph, and undergoes an abrupt iron(II) spin-state crossover from high spin to low spin upon cooling below ca. 130 K. The crystal structure of the methylene chloride solvate of Fe[(p-IC 6 H 4 )B(3-Mepz) 3 ] 2 has a similar stacked two-dimensional supramolecular structure, but the crystals readily lose the solvate. The resulting desolvate undergoes a gradual spin-state crossover to the low-spin state upon cooling below ca. 235 K. It is clear from a comparison of the structures that the long-range solid-state organization of the molecules, which is controlled by noncovalent supramolecular interactions, has a strong impact upon the spin-state crossover, with the more highly organized structures having lower spin-crossover temperatures and more abrupt spin-crossover behavior.

KW - Boron

KW - Carbon

KW - Dichloromethane

KW - Hydrogen

KW - Iron

KW - Iron Derivative

KW - Ligand

KW - Poly(Pyrazolyl)borate Iron

KW - Pyrazine Derivative

KW - Pyrazolyl

KW - Unclassified Drug

KW - Chemical Reaction

KW - Chemical Structure

KW - Crystal Structure

KW - Crystallization

KW - Magnetism

KW - Molecular Interaction

KW - Mössbauer Spectroscopy

KW - Nuclear Magnetic Resonance

KW - Solid State

KW - Synthesis

KW - Temperature

KW - X Ray Crystallography

UR - https://scholarsmine.mst.edu/chem_facwork/125

UR - https://doi.org/10.1021/ic048406q

U2 - 10.1021/ic048406q

DO - 10.1021/ic048406q

M3 - Article

VL - 44

JO - Inorganic Chemistry

JF - Inorganic Chemistry

ER -

Polymorphism in Fe[(p-IC₆H₄)B(3-Mepz)₃]₂ (pz = Pyrazolyl): Impact of Supramolecular Structure on an Iron(II) Electronic Spin-State Crossover

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