Dissertation

|3.1 Brominated Phenanthrolines - A Gate to new Bridging Ligands|
45 000
1.0
37 500
/ l mol -1 cm -1
30 000
22 500
15 000
0.5
Relative Emission / a.u.
7 500
0
300 400 500 600 700 800
Wavelength / nm
0
Figure 53: Absorption spectra of Ru(phenCl) and the [Ru(tbbpy) 2 (phenBr m )] 2+ -complexes
(m = 1, 2) in dichloromethane and corresponding concentration independent relative emission in
dichloromethane and acetonitrile upon excitation at 467 nm. Ru(phenBr): Abs. (DCM) (—), Em. (DCM)
(---), Em. (ACN) (– –), Ru(phenBr 2 ): Abs. (DCM) (—), Em. (DCM) (---), Em. (ACN) (– –) and reference
Ru(phenCl) (phenCl = 5-chloro-1,10-phenanthroline): Abs. (DCM) (—), Em. (DCM) (---) Em. (ACN) (– –) .
state energy of the resulting ruthenium complex. The (-I/+M) effect of the bromo substituents
lowers the energy of the ligand centered π*-orbitals, making them easier to reduce. According to
the emission data, it was figured that substitution in 5,6-position has less influence on the excited
state energy than substitution in the 3,8-position.
3.1.5 Emission Decay Dynamics
The determination of the emission decay dynamics of the 3 MLCT states of the complexes with time
correlated single photon count experiments (TCSPC) in acetonitrile and dichloromethane reflect
the findings of the emission data of increased emission intensity in dichloromethane solutions (see
table 5). Generally, the lifetimes in aerated solutions of dichloromethane (τ ACN ≈ 450 ns) are longer
than lifetimes in aerated acetonitrile (τ DCM ≈ 140 ns), which can be attributed to the dependency
on the quencher (triplet oxygen) concentration in the more polar solvent. A result of this, an
increased lifetime in deaerated acetonitrile (τ deaerated ≈ 1500 ns) was observed due to the decrease
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