Inter- and intramolecular quenching of the singlet excited state of porphyrins by ferrocene
- Massachusetts Inst. of Technology, Cambridge (United States)
Inter- and intramolecular quenching of the lowest singlet excited state of three porphyrins by ferrocene derivatives is reported. 5,15-Bis(4-tolyl)-2,3,7,8,12,13,17,18-octamethylporphyrin (1) and two derivatives of 1 where one of the tolyl methyl groups was replaced by a ferrocenylvinyl group, 2, or by a ferrocenylethyl group, 3, were prepared. Porphyrin 2 was isolated as a mixture of cis (73%) and trans (27%) isomers. Singlet excited state properties were studied by steady-state emission spectroscopy and by emission lifetime measurements. The relative quantum yields of fluorescence for 2 and 3 compared to 1 are 0.38 and 0.84, respectively. Fluorescence decay lifetimes of 1 and 3 are 15 and 14 ns, respectively. Fluorescence of 2 is revealed to be due to the emission of two species (cis and trans isomers) with lifetimes of 4 and 13 ns. The shorter fluorescence lifetimes and smaller fluorescence quantum yields for 2 and 3 compared to 1 are attributed to quenching of the singlet excited state of the porphyrin by the ferrocenyl centers. However, the fraction of quenching by electron transfer and energy transfer could not be quantitatively measured. The rate constant for quenching is no more than 10[sup 8] s[sup [minus]1], consistent with electron-transfer quenching. Intermolecular quenching rate constants for the quenching of the porphyrin singlet excited state by ferrocene derivatives were also found to be consistent with an electron transfer quenching mechanism. 28 refs., 3 figs., 1 tab.
- OSTI ID:
- 6152398
- Journal Information:
- Journal of Physical Chemistry; (United States), Vol. 97:11; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
PORPHYRINS
EXCITED STATES
FLUORESCENCE
ABSORPTION SPECTROSCOPY
ELECTRON TRANSFER
ELECTRONIC STRUCTURE
EMISSION SPECTROSCOPY
FERROCENE
ISOMERS
PHOTOCHEMISTRY
VOLTAMETRY
CARBOXYLIC ACIDS
CHEMISTRY
COMPLEXES
DIENES
ENERGY LEVELS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
IRON COMPLEXES
LUMINESCENCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
POLYENES
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
400500* - Photochemistry
400201 - Chemical & Physicochemical Properties
400102 - Chemical & Spectral Procedures