Excited-state photophysics of donor-appended cobalt(II) porphyrins from picosecond transient absorption spectroscopy

Journal Article · Thu Sep 02 00:00:00 EDT 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100137a022· OSTI ID:5424493

Loppnow, G R; Melamed, D; Leheny, A R; Hamilton, A D; Spiro, T G ^[1]

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1. Princeton Univ., NJ (United States)

Picosecond absorption spectra, obtained with 4-ps pump and probe pulses, are reported for the Co(II) complex of octaethylporphyrin (OEP) and of octaalkylporphyrins with single meso substituents: phenyl, N,N,N[prime],N[prime]-tetramethyl-p-phenylenediamine (TMPD), dimethylaniline-N,N,N[prime],N[prime]-tetramethyl-p-phenylenedia mine (DMA-TMPD), or a phenyl-TMPD. The donor substituents were attached in order to to investigate the possibility of transferring charge to the putative Co[sup (I)]P[sup +] species transiently formed in the excited-state deactivation of cobalt(II) porphyrins, thereby increasing the lifetime of a Co(I) phototransient. The substituents shifted the porphyrin ground-state absorption bands only slightly, and the redox potentials of the constituent parts of the constructs were essentially unaffected by the substitution. For all of the cobalt(II) porphyrins, photoexcitation produced transient bleaching of the ground-state Soret band and an induced absorption at ca. 410 nm. Ground-state recovery was complete within 50 ps in all cases. The lifetime of the phototransient was determined to be 12 [+-] 4 ps for OEP, as well as all the meso-substituted octaalkylporphyrins. 35 refs., 10 figs., 1 tab.

• DOE Contract Number: FG02-88ER13876
• OSTI ID: 5424493
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 97:35; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
COBALT COMPLEXES
ABSORPTION SPECTROSCOPY
ELECTRONIC STRUCTURE
PHOTOCHEMISTRY
ORGANOMETALLIC COMPOUNDS
PORPHYRINS
REDOX PROCESS
VOLTAMETRY
CARBOXYLIC ACIDS
CHEMISTRY
COMPLEXES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
REPROCESSING
SEPARATION PROCESSES
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400500 - Photochemistry
400102 - Chemical & Spectral Procedures