Electronic states and optical properties of porphyrins in van der Waals contact: Th{sup IV} sandwich complexes

Journal Article · Wed Jul 29 00:00:00 EDT 1992 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja00042a037· OSTI ID:457075

Bilsel, O; Rodriguez, J; Holten, D ^[1]

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1. Washington Univ., St. Louis, MO (United States); and others

Ground-state and time-resolved excited-state absorption spectra and fluorescence and phosphorescence spectra of three Th{sup IV} sandwich complexes, Th{sup IV}(TPP){sub 2}, Th{sup IV}(OEP){sub 2}, and Th{sup IV}(OEP)(TPP), are reported (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrinate, TPP = 5,10,15,20-tetraphenylporphyrinate). These complexes, in which the nitrogen planes of the two porphyrin macrocycles are {approximately}2.9 {Angstrom} apart, exhibit a number of prominent optical characteristics: (1) monoporphyrin-like Q and B absorption bands, (2) a new absorption between the Q and B bands, (3) a weak, low-energy absorption that is substantially red-shifted relative to the Q bands of analogous monoporphyrin complexes, (4) fluorescence and phosphorescence emission bands that are even further red-shifted relative to typical emission bands from porphyrin monomers, and (5) a moderately intense near-infrared {sup 3}({pi},{pi}*) excited-state absorption not observed in monomeric porphyrins. These characteristic optical properties of the sandwich complexes are all accounted for by a relatively simple molecular orbital configuration-interaction model. Additionally, the spectral data and molecular orbital model identify the energies of charge-transfer configurations and delineate their contribution to the electronic states of these strongly-coupled {pi} systems. These results provide insights into the interactions that can take place between other pairs of chromophores brought within van der Waals contact, such as the bacteriochlorophyll dimer of the photosynthetic reaction center. 49 refs., 9 figs., 1 tab.

• Sponsoring Organization: USDOE
• OSTI ID: 457075
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 16 Vol. 114; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CONFIGURATION INTERACTION
ELECTRONIC STRUCTURE
ENERGY ABSORPTION
EXCITED STATES
FLUORESCENCE
OPTICAL PROPERTIES
PORPHYRINS
THORIUM COMPLEXES