Toward Organic Synthesis of a Magnetic Particle: Dendritic Polyradicals with 15 and 31 Centers for Unpaired Electrons

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Abstract

Starting from a bromo triether derivative 1, we prepared a homologous pentadecaether, which is a precursor for the title pentadecaradical, by repeating twice the following two-step procedure (total of four steps): (1) Br/Li exchange followed by the addition of the organolithium to a benzoic acid ester derivative and (2) conversion of the triarylmethyl alcohol to methyl ether. Similarly, a 31-ether precursor was prepared by repeating three times the above sequence (total of six steps). The polyethers were converted with lithium metal in THF to the corresponding carbopolyanions and, subsequently, oxidized with iodine at 180 K to give the polyradicals. The polyradicals were studied in frozen THF and 2-MeTHF solutions by SQUID magnetometry in the 2–80 K temperature range and the 0–5.5-T magnetic field range; spin values, which are lower than expected for strong ferromagnetic coupling, were obtained. One of the possible explanations is the presence of defects, which disrupt ferromagnetic coupling between the triarylmethyl sites in these single-path π-conjugated systems; relationship of the current work to the percolation problem is discussed.

Original languageEnglish (US)
Pages (from-to)10688-10694
Number of pages7
JournalJournal of the American Chemical Society
Volume115
Issue number23
DOIs
StatePublished - Nov 1 1993

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Magnetometry
Synthetic Chemistry Techniques
Methyl Ethers
Benzoic Acid
Magnetic Fields
Lithium
Iodine
Ether
Ethers
Esters
Metals
Alcohols
Electrons
Derivatives
Temperature
Benzoic acid
Polyethers
SQUIDs
Magnetic fields
Defects

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

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title = "Toward Organic Synthesis of a Magnetic Particle: Dendritic Polyradicals with 15 and 31 Centers for Unpaired Electrons",
abstract = "Starting from a bromo triether derivative 1, we prepared a homologous pentadecaether, which is a precursor for the title pentadecaradical, by repeating twice the following two-step procedure (total of four steps): (1) Br/Li exchange followed by the addition of the organolithium to a benzoic acid ester derivative and (2) conversion of the triarylmethyl alcohol to methyl ether. Similarly, a 31-ether precursor was prepared by repeating three times the above sequence (total of six steps). The polyethers were converted with lithium metal in THF to the corresponding carbopolyanions and, subsequently, oxidized with iodine at 180 K to give the polyradicals. The polyradicals were studied in frozen THF and 2-MeTHF solutions by SQUID magnetometry in the 2–80 K temperature range and the 0–5.5-T magnetic field range; spin values, which are lower than expected for strong ferromagnetic coupling, were obtained. One of the possible explanations is the presence of defects, which disrupt ferromagnetic coupling between the triarylmethyl sites in these single-path π-conjugated systems; relationship of the current work to the percolation problem is discussed.",
author = "Andrzej Rajca and Suchada Utamapanya",
year = "1993",
month = "11",
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T2 - Dendritic Polyradicals with 15 and 31 Centers for Unpaired Electrons

AU - Rajca, Andrzej

AU - Utamapanya, Suchada

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Y1 - 1993/11/1

N2 - Starting from a bromo triether derivative 1, we prepared a homologous pentadecaether, which is a precursor for the title pentadecaradical, by repeating twice the following two-step procedure (total of four steps): (1) Br/Li exchange followed by the addition of the organolithium to a benzoic acid ester derivative and (2) conversion of the triarylmethyl alcohol to methyl ether. Similarly, a 31-ether precursor was prepared by repeating three times the above sequence (total of six steps). The polyethers were converted with lithium metal in THF to the corresponding carbopolyanions and, subsequently, oxidized with iodine at 180 K to give the polyradicals. The polyradicals were studied in frozen THF and 2-MeTHF solutions by SQUID magnetometry in the 2–80 K temperature range and the 0–5.5-T magnetic field range; spin values, which are lower than expected for strong ferromagnetic coupling, were obtained. One of the possible explanations is the presence of defects, which disrupt ferromagnetic coupling between the triarylmethyl sites in these single-path π-conjugated systems; relationship of the current work to the percolation problem is discussed.

AB - Starting from a bromo triether derivative 1, we prepared a homologous pentadecaether, which is a precursor for the title pentadecaradical, by repeating twice the following two-step procedure (total of four steps): (1) Br/Li exchange followed by the addition of the organolithium to a benzoic acid ester derivative and (2) conversion of the triarylmethyl alcohol to methyl ether. Similarly, a 31-ether precursor was prepared by repeating three times the above sequence (total of six steps). The polyethers were converted with lithium metal in THF to the corresponding carbopolyanions and, subsequently, oxidized with iodine at 180 K to give the polyradicals. The polyradicals were studied in frozen THF and 2-MeTHF solutions by SQUID magnetometry in the 2–80 K temperature range and the 0–5.5-T magnetic field range; spin values, which are lower than expected for strong ferromagnetic coupling, were obtained. One of the possible explanations is the presence of defects, which disrupt ferromagnetic coupling between the triarylmethyl sites in these single-path π-conjugated systems; relationship of the current work to the percolation problem is discussed.

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