title: Substitution-controlled ultrafast excited-state processes in Ru-dppz-derivatives.
abstract: Ru-dppz (dppz = dipyrido[3,2-a:2',3,3'-c]phenazine) complexes play an important role as environmentally sensitive luminescence sensors and building blocks for larger supramolecular compounds. Their photophysical properties are known to be highly sensitive to intermolecular solvent-solute interactions and solvent bulk-properties. Here, the synthesis and characterisation of a novel Ru-dppz derivative is reported. The potential of drastically tuning the photophysical properties of such complexes is exemplified, by introducing very simple structural modifications, namely bromine, into the dppz-ligand scaffold. The photophysics i.e. nature of excited states and the excited-state relaxation pathway of the various complexes has been investigated by means of electrochemical measurements, steady-state emission experiments and femtosecond time-resolved spectroscopy. It could be shown that the location of bromine substitution influences the relative energy between a luminescent and a non-luminescent metal-to-ligand charge-transfer state and therefore quenches or facilitates transitions between both. Hence it is illustrated that the luminescent properties and the underlying ultrafast excited-state dynamics of the complexes can be controlled by structural variations, i.e. by intramolecular interactions as opposed to changes in the intermolecular interactions.
authors.affiliation: Institute of Physical Chemistry, Friedrich-Schiller-University Jena, Helmholtzweg 4, 07743 Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Kuhnt
authors.forename: Michael
authors.initials: M
authors.lastname: Karnahl
authors.forename: Stefanie
authors.initials: S
authors.lastname: Tschierlei
authors.forename: Kristin
authors.initials: K
authors.lastname: Griebenow
authors.forename: Michael
authors.initials: M
authors.lastname: Schmitt
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schäfer
authors.forename: Sven
authors.initials: S
authors.lastname: Krieck
authors.forename: Helmar
authors.initials: H
authors.lastname: Görls
authors.forename: Sven
authors.initials: S
authors.lastname: Rau
authors.forename: Benjamin
authors.initials: B
authors.lastname: Dietzek
authors.forename: Jürgen
authors.initials: J
authors.lastname: Popp