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

Chromium Manifold Phen Acac Kato 

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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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