Picosecond kinetic study of the excited-state properties of some osmium octaethylporphyrins

Journal Article · Wed Jan 13 04:00:00 EST 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00365a045· OSTI ID:5680159

Serpone, N; Netzel, T L; Gouterman, M

Four osmium porphyrin complexes, Os(OEP)LL'((OEP) = octaethylporphyrin), have been investigated by picosecond laser flash photolysis using a double-beam, mode-locked Nd:glass system delivering 6-ps (fwhm) pulses at 527 nm with 1-2 mJ/pulse. Time-resolved excited-state spectra were recorded from the time of photolysis to 5 ns after photolysis. For the four compounds studied (Os(OEP)(P(OMe)/sub 3/)/sub 2/, Os(OEP)CO(py), Os(OEP)NO(OMe), and Os(OEP)O/sub 2/((Me = methyl, py = pyridine, and O/sub 2/ = dioxo)), the initial excited state, S/sub 1/, decayed in less than or equal to8, approx.50, approx.36, and approx.13 ps, respectively. The yields of the later excited state, T/sub 1/, were approx.0.8, unmeasurable, approx.0.6, and approx.1.0, respectively. The T/sub 1/ states lived for times 6.2, 16, 5.5, and 6 ns, respectively. A third relaxation time of approx.15 ps was found for Os(OEP)NO(OMe). The lowest energy excited states for the first two complexes were previously identified as (d,..pi..*) and for the second two as (..pi..,..pi..*) and a red shift of the excited-state absorption of the former with respect to the latter is observed. For the two molecules with lowest energy (..pi..,..pi..*) states, S/sub 1/ and T/sub 1/ are identified as /sup 1/(..pi..,..pi..*) and /sup 3/(..pi..,..pi..*), i.e., singlet and triplet states. For the two molecules with lowest energy (d,..pi..*) states, spin should not be a good quantum number, and S/sub 1/ is identified as a limited set of (d,..pi..*) states produced after subpicosecond relaxation of the initial photoexcited /sup 1/(..pi..,..pi..*) state.

• Research Organization: Brookhaven National Lab., Upton, NY
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5680159
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 104:1; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CARBOXYLIC ACIDS
CHEMICAL REACTION KINETICS
COMPLEXES
DATA
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
KINETICS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OSMIUM COMPLEXES
PORPHYRINS
REACTION KINETICS
SPECTRA
TRANSITION ELEMENT COMPLEXES
WAVELENGTHS