Photochemistry and Photophysics of Coordination Compounds

52 N.A.P. Kane-Maguire
Fig. 13 Qualitative potential energy level diagram for Oh Cr(III) complexes showing possible
radiationless 2 Eg relaxation processes, including a direct deactivation to the ground
state, b back-intersystem crossing (BISC), c direct doublet reaction, or d surface crossing
to a ground state intermediate surface (GSI)
be minimal). The proposed mechanism for this photodeuteration is shown in
Fig. 14.
Fig. 14 Possible mechanism for photoinitiated macrocyclic N – H deuteration in acidic
aqueous solution
A related paper on the corresponding difluorosystems has recently been
published [75].
6
Energy Transfer Studies
Cr(III) complexes were employed as acceptor species in room temperature
energy transfer experiments between transition metal complexes as early as
1972 [21, 76], and several years later the first cases appeared where the donor
and acceptor were both Cr(III) compounds [77, 78]. In the survey since 1999,
eight articles were identified where energy transfer studies involving Cr(III)
species were the primary research activity [79–86]. The paper chosen for
discussion in Sect. 6.1 describes the first report of electronic energy selfexchange
between Cr(III) complexes [81].