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Multiphoton-Induced Picosecond Photophysics of Chromium(III)- Polypyridyl Complexes

  • N. Serpone
  • M. Z. Hoffman
Conference paper

Abstract

The photophysics of Cr(III)-polypyridyl complexes, Cr(NN)3 3+, have been the object of many studies in attempts at understanding the behaviour of these systems on absorption of light (Jamieson 1981; Serpone 1983). The usual photochemically relevant states of Cr(NN)3 3+ (Fig. 1) are: the ground state, \({\!^4{\text{A}}_2}\); the lowest energy spin-allowed quartet state, \({\!^4{\text{T}}_2}\); and the lowest energy spin-forbidden doublet states, \({\!^2{\text{T}}_1}/ {\!^2{\text{E}}}\). Also, shown are the other higher energy quartet and doublet states, and the ligand-centred states (Ohno 1983 1986) depicted as dashed curves? not shown are some 12 additional doublet states. Several studies have been
Fig. 1

Qualitative energy level diagram as a function of a distort- ion coordinate. Solid lines denote metal-centred state surfaces; dashed lines show ligand-centred surfaces. From (Serpone 1987).

directed toward the long-lived (τ ~ 0.1 - 1 ms) luminescent \({\!^2{\text{T}}_1}/ {\!^2{\text{E}}}\) states; prompt fluorescence from \({\!^4{\text{T}}_2}\) has not been observed in fluid media at ambient temperatures, implying either that the lifetime of \({\!^4{\text{T}}_2}\) is too short or that this state is not populated. Recent pulsed laser transient absorption spectroscopy experiments have indicated that τ of \({\!^4{\text{T}}_2}\) of Cr(acac)3, Cr(NCS)6 3-, t-Cr(NH3)2(NCS)4 -, t-Cr(en)2(NCS)2 +, Cr(en)3 3+, and Cr(bpy)3 3+ are a few ps or less (Kirk 1976; Rojas 1986 1987; Pyke 1978; I.eSage 1983 ; Nicollin 1980).

Keywords

Transient Absorption Transient Absorption Spectrum Doublet State Polypyridyl Complex Transient Emission 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

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Copyright information

© Springer-Verlag Berlin · Heidelberg 1987

Authors and Affiliations

  • N. Serpone
    • 1
  • M. Z. Hoffman
    • 2
  1. 1.Department of ChemistryConcordia UniversityMontrealCanada
  2. 2.Department of ChemistryBoston UniversityBostonUSA

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