Tetraazacyclophanes by Palladium-Catalyzed Aromatic Amination. Geometrically Defined, Stable, High-Spin Diradicals
摘要:
[GRAPHICS]Neutral tetraazacyclophanes were prepared in a one-step palladium-catalyzed amination reaction, Simple oxidation of these materials creates dication diradicals that are stable at room temperature and that are geometrically well defined. The electronic and magnetic properties of the dications were investigated by CV, UV-vis, and EPR spectroscopy. These spectral data and solution phase magnetic susceptibility measurements indicate high spin ground states in certain media. EPR zero field splitting parameters for the diradical suggest that the distance between the two radical sites can be approximated simply by the distance between alternating nitrogens in the macrocycle.
Tetraazacyclophanes by Palladium-Catalyzed Aromatic Amination. Geometrically Defined, Stable, High-Spin Diradicals
摘要:
[GRAPHICS]Neutral tetraazacyclophanes were prepared in a one-step palladium-catalyzed amination reaction, Simple oxidation of these materials creates dication diradicals that are stable at room temperature and that are geometrically well defined. The electronic and magnetic properties of the dications were investigated by CV, UV-vis, and EPR spectroscopy. These spectral data and solution phase magnetic susceptibility measurements indicate high spin ground states in certain media. EPR zero field splitting parameters for the diradical suggest that the distance between the two radical sites can be approximated simply by the distance between alternating nitrogens in the macrocycle.
best modeled by 1D spin S = 1 Heisenberg chain with intrachain antiferromagnetic coupling of J'/ k = -5.4 K, which is associated with the interaryl C···C contacts, including π-π interactions. Zero-field splitting value, | D/ hc| ≈ 5.6 × 10-3 cm-1, for 12·2+ is rather small; thus, the 1D chains are characterized by the high degree of isotropicity | D/2 J'| ≈ 7.5 × 10-4. The diradical dication salt possesses
Tetraazacyclophanes by Palladium-Catalyzed Aromatic Amination. Geometrically Defined, Stable, High-Spin Diradicals
作者:Sheila I. Hauck、K. V. Lakshmi、John F. Hartwig
DOI:10.1021/ol9912276
日期:1999.12.1
[GRAPHICS]Neutral tetraazacyclophanes were prepared in a one-step palladium-catalyzed amination reaction, Simple oxidation of these materials creates dication diradicals that are stable at room temperature and that are geometrically well defined. The electronic and magnetic properties of the dications were investigated by CV, UV-vis, and EPR spectroscopy. These spectral data and solution phase magnetic susceptibility measurements indicate high spin ground states in certain media. EPR zero field splitting parameters for the diradical suggest that the distance between the two radical sites can be approximated simply by the distance between alternating nitrogens in the macrocycle.