Molecular structure and magnetic properties of 1-ethyl-2-(1-oxy-3-oxo-4,4, 5,5-tetramethylimidazolin-2-yl)-3-methylimidazolium arylcarboxylates and other salts

Hiroyuki Hayashi, Satoru Karasawa, Noboru Koga

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

(Chemical Equation Presented) 1-Ethyl-2-(1-oxy-3-oxo-4,4,5,5- tetramethylimidazolin-2-yl)-3-methylimidazolium bromide, [EMINN] +[Br]-, carrying nitronylnitroxide (NN) in the cation unit, was prepared as a parent molecule and converted to seven salts, [EMINN]+[X]- (X = I, TFSI (bis(trifluoromethanesulfonyl) imide), BPh4 (tetraphenylborate), [EMINN]+ 1-3[BA1-3](1-3)-; BA1 (benzoic acid), BA2 (terephthalic acid), and BA3 (trimesic acid), and [EMINN]+[BANN]-; BANN (4-NN-benzoic acid)), by the ion-exchange reaction. The molecular structure of the cation units for all salts revealed by X-ray crystallography is similar, where the dihedral angles between the imidazolium ring and the NN planes are 51-58°. In the crystal structure, [EMINN]+[X]- (X = Br, I, TFSI, and BPh 4) formed head-to-tail dimers, while the uniquely shaped dimers consisting of two [EMINN]+[carboxylate]- units were connected by the hydrogen bonding of water molecules to form a tape structure for [EMINN]+[BANN]- and 2D sheet structure for [EMINN]+2[BA2]2- and [EMINN] +3[BA3]3-. In the crystalline state, [EMINN]+[X]- showed behavior typical of a paramagnetic species with S = 1/2. The χmolT vs T plot for [EMINN] +[BANN]- was analyzed using a four-spin model to give J1/kB = -0.27 and J2/kB = -0.16 K. The plots for [EMINN]+2[BA2]2- and [EMINN]+3[BA3]3- were analyzed using an antiferromagnetic chain model to give J/kB = -62.1 and -86.5 K, respectively. In aqueous solution, on the other hand, the ESR spectra for all salts showed similar five-line signals due to the isolated NN moiety. The relaxivities (r1 and r2; 25°C, 0.59 T, and 25 MHz) for [EMINN]+[Br]-, [EMINN]+[BA]-, [EMINN]+[BANN]-, [EMINN]+2[BA 2]2-, and [EMINN]+3[BA 3]3-, are r1 = 0.13, 0.14, 0.32, 0.26, and 0.40 and r2 = 0.17, 0.13, 0.31, 0.30, and 0.46 mM-1 s -1, respectively.

Original languageEnglish
Pages (from-to)8683-8693
Number of pages11
JournalJournal of Organic Chemistry
Volume73
Issue number22
DOIs
Publication statusPublished - Nov 21 2008

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Molecular structure
Magnetic properties
Benzoic Acid
Salts
Dimers
Cations
Tetraphenylborate
Molecules
X ray crystallography
Dihedral angle
Bromides
Tapes
Paramagnetic resonance
Ion exchange
Hydrogen bonds
Crystal structure
Crystalline materials
Water
bis(trifluoromethanesulfonyl)imide
terephthalic acid

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

Cite this

Molecular structure and magnetic properties of 1-ethyl-2-(1-oxy-3-oxo-4,4, 5,5-tetramethylimidazolin-2-yl)-3-methylimidazolium arylcarboxylates and other salts. / Hayashi, Hiroyuki; Karasawa, Satoru; Koga, Noboru.

In: Journal of Organic Chemistry, Vol. 73, No. 22, 21.11.2008, p. 8683-8693.

Research output: Contribution to journalArticle

@article{893d0795c3214c9b849d265bec940c46,
title = "Molecular structure and magnetic properties of 1-ethyl-2-(1-oxy-3-oxo-4,4, 5,5-tetramethylimidazolin-2-yl)-3-methylimidazolium arylcarboxylates and other salts",
abstract = "(Chemical Equation Presented) 1-Ethyl-2-(1-oxy-3-oxo-4,4,5,5- tetramethylimidazolin-2-yl)-3-methylimidazolium bromide, [EMINN] +[Br]-, carrying nitronylnitroxide (NN) in the cation unit, was prepared as a parent molecule and converted to seven salts, [EMINN]+[X]- (X = I, TFSI (bis(trifluoromethanesulfonyl) imide), BPh4 (tetraphenylborate), [EMINN]+ 1-3[BA1-3](1-3)-; BA1 (benzoic acid), BA2 (terephthalic acid), and BA3 (trimesic acid), and [EMINN]+[BANN]-; BANN (4-NN-benzoic acid)), by the ion-exchange reaction. The molecular structure of the cation units for all salts revealed by X-ray crystallography is similar, where the dihedral angles between the imidazolium ring and the NN planes are 51-58°. In the crystal structure, [EMINN]+[X]- (X = Br, I, TFSI, and BPh 4) formed head-to-tail dimers, while the uniquely shaped dimers consisting of two [EMINN]+[carboxylate]- units were connected by the hydrogen bonding of water molecules to form a tape structure for [EMINN]+[BANN]- and 2D sheet structure for [EMINN]+2[BA2]2- and [EMINN] +3[BA3]3-. In the crystalline state, [EMINN]+[X]- showed behavior typical of a paramagnetic species with S = 1/2. The χmolT vs T plot for [EMINN] +[BANN]- was analyzed using a four-spin model to give J1/kB = -0.27 and J2/kB = -0.16 K. The plots for [EMINN]+2[BA2]2- and [EMINN]+3[BA3]3- were analyzed using an antiferromagnetic chain model to give J/kB = -62.1 and -86.5 K, respectively. In aqueous solution, on the other hand, the ESR spectra for all salts showed similar five-line signals due to the isolated NN moiety. The relaxivities (r1 and r2; 25°C, 0.59 T, and 25 MHz) for [EMINN]+[Br]-, [EMINN]+[BA]-, [EMINN]+[BANN]-, [EMINN]+2[BA 2]2-, and [EMINN]+3[BA 3]3-, are r1 = 0.13, 0.14, 0.32, 0.26, and 0.40 and r2 = 0.17, 0.13, 0.31, 0.30, and 0.46 mM-1 s -1, respectively.",
author = "Hiroyuki Hayashi and Satoru Karasawa and Noboru Koga",
year = "2008",
month = "11",
day = "21",
doi = "10.1021/jo801657a",
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journal = "Journal of Organic Chemistry",
issn = "0022-3263",
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T1 - Molecular structure and magnetic properties of 1-ethyl-2-(1-oxy-3-oxo-4,4, 5,5-tetramethylimidazolin-2-yl)-3-methylimidazolium arylcarboxylates and other salts

AU - Hayashi, Hiroyuki

AU - Karasawa, Satoru

AU - Koga, Noboru

PY - 2008/11/21

Y1 - 2008/11/21

N2 - (Chemical Equation Presented) 1-Ethyl-2-(1-oxy-3-oxo-4,4,5,5- tetramethylimidazolin-2-yl)-3-methylimidazolium bromide, [EMINN] +[Br]-, carrying nitronylnitroxide (NN) in the cation unit, was prepared as a parent molecule and converted to seven salts, [EMINN]+[X]- (X = I, TFSI (bis(trifluoromethanesulfonyl) imide), BPh4 (tetraphenylborate), [EMINN]+ 1-3[BA1-3](1-3)-; BA1 (benzoic acid), BA2 (terephthalic acid), and BA3 (trimesic acid), and [EMINN]+[BANN]-; BANN (4-NN-benzoic acid)), by the ion-exchange reaction. The molecular structure of the cation units for all salts revealed by X-ray crystallography is similar, where the dihedral angles between the imidazolium ring and the NN planes are 51-58°. In the crystal structure, [EMINN]+[X]- (X = Br, I, TFSI, and BPh 4) formed head-to-tail dimers, while the uniquely shaped dimers consisting of two [EMINN]+[carboxylate]- units were connected by the hydrogen bonding of water molecules to form a tape structure for [EMINN]+[BANN]- and 2D sheet structure for [EMINN]+2[BA2]2- and [EMINN] +3[BA3]3-. In the crystalline state, [EMINN]+[X]- showed behavior typical of a paramagnetic species with S = 1/2. The χmolT vs T plot for [EMINN] +[BANN]- was analyzed using a four-spin model to give J1/kB = -0.27 and J2/kB = -0.16 K. The plots for [EMINN]+2[BA2]2- and [EMINN]+3[BA3]3- were analyzed using an antiferromagnetic chain model to give J/kB = -62.1 and -86.5 K, respectively. In aqueous solution, on the other hand, the ESR spectra for all salts showed similar five-line signals due to the isolated NN moiety. The relaxivities (r1 and r2; 25°C, 0.59 T, and 25 MHz) for [EMINN]+[Br]-, [EMINN]+[BA]-, [EMINN]+[BANN]-, [EMINN]+2[BA 2]2-, and [EMINN]+3[BA 3]3-, are r1 = 0.13, 0.14, 0.32, 0.26, and 0.40 and r2 = 0.17, 0.13, 0.31, 0.30, and 0.46 mM-1 s -1, respectively.

AB - (Chemical Equation Presented) 1-Ethyl-2-(1-oxy-3-oxo-4,4,5,5- tetramethylimidazolin-2-yl)-3-methylimidazolium bromide, [EMINN] +[Br]-, carrying nitronylnitroxide (NN) in the cation unit, was prepared as a parent molecule and converted to seven salts, [EMINN]+[X]- (X = I, TFSI (bis(trifluoromethanesulfonyl) imide), BPh4 (tetraphenylborate), [EMINN]+ 1-3[BA1-3](1-3)-; BA1 (benzoic acid), BA2 (terephthalic acid), and BA3 (trimesic acid), and [EMINN]+[BANN]-; BANN (4-NN-benzoic acid)), by the ion-exchange reaction. The molecular structure of the cation units for all salts revealed by X-ray crystallography is similar, where the dihedral angles between the imidazolium ring and the NN planes are 51-58°. In the crystal structure, [EMINN]+[X]- (X = Br, I, TFSI, and BPh 4) formed head-to-tail dimers, while the uniquely shaped dimers consisting of two [EMINN]+[carboxylate]- units were connected by the hydrogen bonding of water molecules to form a tape structure for [EMINN]+[BANN]- and 2D sheet structure for [EMINN]+2[BA2]2- and [EMINN] +3[BA3]3-. In the crystalline state, [EMINN]+[X]- showed behavior typical of a paramagnetic species with S = 1/2. The χmolT vs T plot for [EMINN] +[BANN]- was analyzed using a four-spin model to give J1/kB = -0.27 and J2/kB = -0.16 K. The plots for [EMINN]+2[BA2]2- and [EMINN]+3[BA3]3- were analyzed using an antiferromagnetic chain model to give J/kB = -62.1 and -86.5 K, respectively. In aqueous solution, on the other hand, the ESR spectra for all salts showed similar five-line signals due to the isolated NN moiety. The relaxivities (r1 and r2; 25°C, 0.59 T, and 25 MHz) for [EMINN]+[Br]-, [EMINN]+[BA]-, [EMINN]+[BANN]-, [EMINN]+2[BA 2]2-, and [EMINN]+3[BA 3]3-, are r1 = 0.13, 0.14, 0.32, 0.26, and 0.40 and r2 = 0.17, 0.13, 0.31, 0.30, and 0.46 mM-1 s -1, respectively.

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