Molecular-Engineered Biradicals Based on the Y III -Phthalocyanine Platform
A mixed-ligand phthalocyanine/porphyrin yttrium(III) radical double-decker complex ( ) was synthesized using the custom-made 5,10,15-tris(4-methoxyphenyl)-20-(4-((trimethylsilyl)ethynyl)phenyl)porphyrin. The trimethylsilyl functionality was then used to couple two such complexes into biradicals thro...
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Published in | Journal of the American Chemical Society Vol. 145; no. 4; pp. 2461 - 2472 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
01.02.2023
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Subjects | |
Online Access | Get full text |
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Summary: | A mixed-ligand phthalocyanine/porphyrin yttrium(III) radical double-decker complex (
) was synthesized using the custom-made 5,10,15-tris(4-methoxyphenyl)-20-(4-((trimethylsilyl)ethynyl)phenyl)porphyrin. The trimethylsilyl functionality was then used to couple two such complexes into biradicals through rigid tethers. Glaser coupling was used to synthesize a short-tethered biradical (
) and Sonogashira coupling to synthesize longer-tethered ones (
and
). Field-swept echo-detected (FSED), saturation recovery, and spin nutation-pulsed electron paramagnetic resonance experiments revealed marked similarities of the magnetic properties of
with those of the parent [Y(pc)
]
complex, both in the solid state and in CD
Cl
/CDCl
4:1 frozen glasses. FSED experiments on the biradicals
and
revealed a spectral broadening with respect to the spectra of
and [Y(pc)
]
assigned to the effect of dipolar interactions in solution. Apart from the main resonance, satellite features were also observed, which were simulated with dipole-dipole pairs of shortest distances, suggesting spin delocalization on the organic tether. FSED experiments on
yielded spectral line shapes that could not be simulated as the integration of the off-resonance echoes was complicated by field-dependent modulations. While, for all dimers, the on-resonance spin nutation experiments yielded Rabi oscillations of the same frequencies, off-resonance nutations on
yielded Rabi oscillations that could be assigned to a
= -1 to
= 0 transition within a
= 1 multiplet. The DFT calculations showed that the
conformation of the complexes was significantly more stable than the cis one and that it induced a marked spin delocalization over the rigid organic tether. This "spin leakage" was most pronounced for the shortest biradical
. |
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ISSN: | 0002-7863 1520-5126 |
DOI: | 10.1021/jacs.2c11760 |