Quantitative Comparison of Kinetic Stabilities of Metallomacroycle-Based Rotaxane

Chang S.-Y., Jang H.-Y, Kyu-Sung Jeong

Research output: Contribution to journalArticle

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Abstract

Four mononuclear metallomacrocycles with identical cavities but different transition metals (OsVI, PdII, PtII, and ReI) were prepared. With these metallomacrocycles, the corresponding rotaxanes 2-Os, 2-Pd, 2-Pt, and 2-Re were self-assembled by hydrogen-bonding interactions. The kinetic stabilities of the rotaxanes were determined quantitatively and compared with each other by 1H NMR spectroscopic techniques, including two-dimensional exchange spectroscopy (2D-EXSY) experiments. The activation free energies (ΔG≠) for the exchange between the rotaxanes 2-Os, 2-Pd and 2-Pt and their free components were determined to be 15.5, 16.0, and 16.4 kcal mol−1, respectively. These magnitudes imply that the rotaxanes 2-Os, 2-Pd and 2-Pt are kinetically labile at room temperature and exist only as equilibrium mixtures with free components in solution. In contrast, the rotaxane 2-Re is kinetically stable enough to be isolated in pure form by silica gel chromatography under ordinary laboratory conditions. However, at higher temperatures (>60 °C) 2-Re was slowly disassembled into its components until the equilibrium was established. The rate constants were measured at three different temperatures, and the Eyring plot yielded the activation enthalpy ΔH≠=35 kcal mol−1 and the activation entropy ΔS≠=27 eu for the disassembly of the rotaxane 2-Re in Cl2CDCDCl2. These thermodynamic parameters gave the activation free energy ΔGequation image=27.1 kcal mol−1 at 25 °C. Consequently, 2-Re is one example of a novel metallomacrocycle-based rotaxane that contains a coordination bond with enough strength to allow both for isolation in pure form around room temperature and for self-assembly at higher temperatures.
Original languageEnglish
Pages (from-to)1535-1541
Number of pages7
JournalChemistry - A European Journal
Volume9
Issue number7
DOIs
Publication statusPublished - 2003 Apr 4

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Rotaxanes
Kinetics
Chemical activation
Free energy
Ion exchange
Temperature
Silica gel
Chromatography
Self assembly
Transition metals
Enthalpy
Rate constants
Hydrogen bonds
Silica Gel
Entropy
Nuclear magnetic resonance
Spectroscopy
Thermodynamics

Cite this

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title = "Quantitative Comparison of Kinetic Stabilities of Metallomacroycle-Based Rotaxane",
abstract = "Four mononuclear metallomacrocycles with identical cavities but different transition metals (OsVI, PdII, PtII, and ReI) were prepared. With these metallomacrocycles, the corresponding rotaxanes 2-Os, 2-Pd, 2-Pt, and 2-Re were self-assembled by hydrogen-bonding interactions. The kinetic stabilities of the rotaxanes were determined quantitatively and compared with each other by 1H NMR spectroscopic techniques, including two-dimensional exchange spectroscopy (2D-EXSY) experiments. The activation free energies (ΔG≠) for the exchange between the rotaxanes 2-Os, 2-Pd and 2-Pt and their free components were determined to be 15.5, 16.0, and 16.4 kcal mol−1, respectively. These magnitudes imply that the rotaxanes 2-Os, 2-Pd and 2-Pt are kinetically labile at room temperature and exist only as equilibrium mixtures with free components in solution. In contrast, the rotaxane 2-Re is kinetically stable enough to be isolated in pure form by silica gel chromatography under ordinary laboratory conditions. However, at higher temperatures (>60 °C) 2-Re was slowly disassembled into its components until the equilibrium was established. The rate constants were measured at three different temperatures, and the Eyring plot yielded the activation enthalpy ΔH≠=35 kcal mol−1 and the activation entropy ΔS≠=27 eu for the disassembly of the rotaxane 2-Re in Cl2CDCDCl2. These thermodynamic parameters gave the activation free energy ΔGequation image=27.1 kcal mol−1 at 25 °C. Consequently, 2-Re is one example of a novel metallomacrocycle-based rotaxane that contains a coordination bond with enough strength to allow both for isolation in pure form around room temperature and for self-assembly at higher temperatures.",
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Quantitative Comparison of Kinetic Stabilities of Metallomacroycle-Based Rotaxane. / S.-Y., Chang; H.-Y, Jang; Jeong, Kyu-Sung.

In: Chemistry - A European Journal, Vol. 9, No. 7, 04.04.2003, p. 1535-1541.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Quantitative Comparison of Kinetic Stabilities of Metallomacroycle-Based Rotaxane

AU - S.-Y., Chang

AU - H.-Y, Jang

AU - Jeong, Kyu-Sung

PY - 2003/4/4

Y1 - 2003/4/4

N2 - Four mononuclear metallomacrocycles with identical cavities but different transition metals (OsVI, PdII, PtII, and ReI) were prepared. With these metallomacrocycles, the corresponding rotaxanes 2-Os, 2-Pd, 2-Pt, and 2-Re were self-assembled by hydrogen-bonding interactions. The kinetic stabilities of the rotaxanes were determined quantitatively and compared with each other by 1H NMR spectroscopic techniques, including two-dimensional exchange spectroscopy (2D-EXSY) experiments. The activation free energies (ΔG≠) for the exchange between the rotaxanes 2-Os, 2-Pd and 2-Pt and their free components were determined to be 15.5, 16.0, and 16.4 kcal mol−1, respectively. These magnitudes imply that the rotaxanes 2-Os, 2-Pd and 2-Pt are kinetically labile at room temperature and exist only as equilibrium mixtures with free components in solution. In contrast, the rotaxane 2-Re is kinetically stable enough to be isolated in pure form by silica gel chromatography under ordinary laboratory conditions. However, at higher temperatures (>60 °C) 2-Re was slowly disassembled into its components until the equilibrium was established. The rate constants were measured at three different temperatures, and the Eyring plot yielded the activation enthalpy ΔH≠=35 kcal mol−1 and the activation entropy ΔS≠=27 eu for the disassembly of the rotaxane 2-Re in Cl2CDCDCl2. These thermodynamic parameters gave the activation free energy ΔGequation image=27.1 kcal mol−1 at 25 °C. Consequently, 2-Re is one example of a novel metallomacrocycle-based rotaxane that contains a coordination bond with enough strength to allow both for isolation in pure form around room temperature and for self-assembly at higher temperatures.

AB - Four mononuclear metallomacrocycles with identical cavities but different transition metals (OsVI, PdII, PtII, and ReI) were prepared. With these metallomacrocycles, the corresponding rotaxanes 2-Os, 2-Pd, 2-Pt, and 2-Re were self-assembled by hydrogen-bonding interactions. The kinetic stabilities of the rotaxanes were determined quantitatively and compared with each other by 1H NMR spectroscopic techniques, including two-dimensional exchange spectroscopy (2D-EXSY) experiments. The activation free energies (ΔG≠) for the exchange between the rotaxanes 2-Os, 2-Pd and 2-Pt and their free components were determined to be 15.5, 16.0, and 16.4 kcal mol−1, respectively. These magnitudes imply that the rotaxanes 2-Os, 2-Pd and 2-Pt are kinetically labile at room temperature and exist only as equilibrium mixtures with free components in solution. In contrast, the rotaxane 2-Re is kinetically stable enough to be isolated in pure form by silica gel chromatography under ordinary laboratory conditions. However, at higher temperatures (>60 °C) 2-Re was slowly disassembled into its components until the equilibrium was established. The rate constants were measured at three different temperatures, and the Eyring plot yielded the activation enthalpy ΔH≠=35 kcal mol−1 and the activation entropy ΔS≠=27 eu for the disassembly of the rotaxane 2-Re in Cl2CDCDCl2. These thermodynamic parameters gave the activation free energy ΔGequation image=27.1 kcal mol−1 at 25 °C. Consequently, 2-Re is one example of a novel metallomacrocycle-based rotaxane that contains a coordination bond with enough strength to allow both for isolation in pure form around room temperature and for self-assembly at higher temperatures.

U2 - 10.1002/chem.200390176

DO - 10.1002/chem.200390176

M3 - Article

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VL - 9

SP - 1535

EP - 1541

JO - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

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