Resonance Raman study of the T{sub 1} excited state of zinc(II) complexes of {beta}-substituted chlorins

Journal Article · Thu Nov 14 04:00:00 EST 1996 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp961190w· OSTI ID:420684

Blackwood, Jr, M E; Kumble, R; Spiro, T G ^[1]

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1. Princeton Univ., NJ (United States)

Nanosecond time-resolved transient absorption (TA) and time-resolved resonance Raman (TR{sup 3}) spectroscopies have been used to study the first triplet excited state, T{sub 1}, of Zn(II) octaethylchlorin (ZnOEC). Additionally, TR{sup 3} spectra are reported for Zn(II) etiochlorin I (ZnEtI) and the meso-d{sub 4} and {sup 15}N isotopomers of ZnOEC. Formation of the T{sub 1} state in ZnOEC results in a red shift of the Soret absorption band from 400 to 421 nm. Features in the resonance Raman spectra of the ground and T{sub 1} state are assigned on the basis of the isotope shift patterns and of normal coordinate analyses of MOECs. Bands at 1464 and 4597 cm {sup -1} in the T{sub 1} spectrum are assigned to C{sub {alpha}}C{sub m} stretching modes, {nu}{sub 3} and {nu}{sub 10} respectively, downshifted by 21 and 19 cm{sup -1} from their ground state frequencies. The only observed C{sub {beta}}C{sub {beta}} stretching mode seen in the T{sub 1} spectrum is at 1542 cm{sup -1} and is assigned to {nu}{sub 2}, downshifted from 1571 cm{sup -1} in the ground state. The C{sub {alpha}}N and C{sub {alpha}}C{sub {beta}} stretching modes located in the 1350-1400 cm{sup -1} region of the ground state downshift in the triplet excited state to an unresolved set of peaks in the 1325-1380 cm{sup -1} region. The frequency downshifts indicate that the observed peaks arise from vibrational modes which are localized on bonds that are weakened in the excited state. 23 refs., 6 figs., 1 tab.

• DOE Contract Number: FG02-93ER14403
• OSTI ID: 420684
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 46 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ABSORPTION SPECTRA
CHEMICAL SHIFT
CHLORINS
EXCITED STATES
GROUND STATES
MOLECULAR STRUCTURE
RAMAN SPECTRA
ZINC COMPLEXES