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Photophysics of lanthanide triple decker porphyrin sandwich complexes

Journal Article · · Journal of Physical Chemistry
DOI:https://doi.org/10.1021/jp952614+· OSTI ID:196653
;  [1]
  1. Washington Univ., St. Louis, MO (United States)
+ Show Author Affiliations

Ground state and time resolved excited state optical absorption spectra and luminescence spectra are reported for La{sub 2}(OEP){sub 3}, Eu{sub 2}(OEP){sub 3}, and Ce{sub 2}(OEP){sub 3} (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrinate). The porphyrin marcrocycles in these molecules are strongly coupled due to their mean separation of = 3.5 A. The triple deckers show many optical properties analogous to those found for double decker porphyrin sandwich complexes, including features not exhibited by porphyrin monomers. Following excitation, the lowest {sup 1}({pi},{pi}{sup *}) state of La{sub 2}(OEP){sub 3} decays in nearly 10ps predominantly to the phosphorescent {sup 3}({pi},{pi}{sup *}) state, which lives for nearly 10 {mu}s. The lowest {sup 1}({pi},{pi}{sup *}) state of Eu{sub 2}(OEP){sub 3} also decays rapidly and with high yield to the lowest {sup 3}({pi},{pi}{sup *}) state, which has a rather short lifetime of 630 ps. The lack of luminescence from Eu{sub 2}(OEP){sub 3} is ascribed to deactivation of the {sup 3}({pi},{pi}{sup *}) state through one or more low-energy ligand-field states of the metal ion. Ce{sub 2}(OEP){sub 3} is also nonluminescent. Unlike La{sub 2}(OEP){sub 3} and Eu{sub 2}(OEP){sub 3}, the {sup 1}({pi},{pi}{sup *}) lifetime of 7 ps for Ce{sub 2}(OEP){sub 3} largely reflects deactivation within the singlet manifold. The decay of {sup 1}({pi},{pi}{sup *}) to the ground state likely involves low-lying (f,f) states, although a charge transfer state may play a role. 22 refs., 9 figs., 1 tab.

OSTI ID:
196653
Journal Information:
Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 2 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
Country of Publication:
United States
Language:
English

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Related Subjects

40 CHEMISTRY
66 PHYSICS
ABSORPTION SPECTRA
CERIUM COMPLEXES
EMISSION SPECTRA
EUROPIUM COMPLEXES
EXCITED STATES
GROUND STATES
LANTHANUM COMPLEXES
LUMINESCENCE
ORGANOMETALLIC COMPOUNDS
PHOTOCHEMISTRY
PORPHYRINS
RARE EARTH COMPLEXES