Studies on monomers and dimers of Y(III) and La(III) porphyrin complexes by time-resolved electron paramagnetic resonance
- Tohoku Univ., Sendai (Japan)
EPR parameters such as zero-field splittings (zfs) and anisotropic g values of rare-earth metal centered porphyrin monomers, Y(TPP){sup +} and Y(OEP){sup +}, and double-decker dimers, [Y(TPP){sub 2}]{sup -}, [Y(OEP){sub 2}]{sup -}, and [La(TPP){sub 2}]{sup -}, were measured in the lowest excited triplet (T{sub 1}) states by a time-resolved electron paramagnetic resonance (TREPR) technique. The zfs parameter D of Y(OEP){sup +} was smaller than that of ZnOEP, and its g{sub zz} was smaller than that of Y(TPP){sup +}. From the analyses of these data and the temperature dependence of the steady state EPR spectra, it was found that the decreases in the D and g{sub zz} values of Y(OEP){sup +} were due to a spin-orbit coupling between the Jahn-Teller split T{sub 1} and T{sub 2} states. By comparing the D values of the dimers with those of the corresponding monomers, we estimated a charge resonance character, b{sup 2}, as 0.34, 0.26, and <0.25 for [Y(OEP){sub 2}]{sup -}, [Y(TPP){sub 2}]{sup -}, and [La(TPP){sub 2}]{sup -}, respectively. The b{sup 2} value was larger for the OEP dimer than those for the TPP dimers. We evaluated the b{sup 2} values using a semiempirical calculation and showed that b{sup 2} was larger for the {sup 3}(a{sub 1u}e{sub g}) electronic configuration than that for the {sup 3}(a{sub 2u}e{sub g}) configuration. 41 refs., 10 figs., 3 tabs.
- OSTI ID:
- 226739
- Journal Information:
- Journal of Physical Chemistry, Vol. 100, Issue 9; Other Information: PBD: 29 Feb 1996
- Country of Publication:
- United States
- Language:
- English
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