Abstract
Reactions of the 16-electron ruthenium complex [Ru(dppe)
2
Cl][PF
6
] with metal-free and zinc ethynylphenyltrifluorenylporphyrins
1
and
2
respectively, gave the new dyads
3
and
4
with ethynylruthenium group as a potential electron donor and the porphyrin as a potential electron acceptor. The redox properties of the porphyrins
1–4
were investigated by cyclic voltammetry and UV spectroelectrochemistry (SEC), which reveal that the monocation and monoanion of metal-free porphyrin
1
are stable under these conditions whereas the formation of the corresponding radical cation or anion of the zinc porphyrin
2
was accompanied by partial decomplexation of the zinc ion. Oxidations of the dyads
3
and
4
gave stable radical cations as probed using IR, NIR and UV SEC methods. These cations show similar NIR and IR bands to those reported for the known 17-electron [Ru(dppe)
2
(CCPh)Cl]
+
radical cation. Remarkably, the dyad
3
has four stable redox states +2/+1/0/−1 where the second oxidation and first reduction processes take place at the porphyrin unit. Simulated absorption spectra on
1–4
at optimised geometries obtained by TD-DFT computations with the CAM-B3LYP functional are shown to be in very good agreement with the observed UV absorption spectra of
1–4
. The spectra of
1–4
and their oxidised and reduced species were interpreted with the aid of the TD-DFT data. Fluorescence measurements reveal that the dyads
3
and
4
are only weakly emitting compared to
1
and
2
, indicative of quenching of the porphyrinic singlet excited state by the ruthenium centre.