Synthesis of trinuclear Pd–Ru–Pd porphyrin complexes with axially ligated Pd centers. Prominent metal-to-ligand charge transfer band in the visible region

•Synthesis of di- and trinuclear porphyrin complex with axially ligated ligands.•MLCT property changes upon introduction of metal units to the ligands.•In the trinuclear Pd–Ru–Pd complex, metal(Ru) to axially ligated ligands takes place.

Ru–porphyrin complexes with pyridylpyrazine as metal coordination sites were synthesized. Introduction of Pd-alkyl units to the binding site led to the formation of a novel Pd–Ru–Pd trinuclear complex. The metalation causes drastic changes in the electrochemical and photophysical properties. The trinuclear complex exhibited a prominent metal-to-axial ligand charge transfer band in the visible region due to small energy gap between the Ru-based HOMO and the axial ligand-based LUMO. These changes resulted in the drastic color change from orange to green.

Graphical abstractRu–porphyrin complexes with pyridylpyrazine as metal coordination sites were synthesized and the introduction of Pd-alkyl units led to the formation of a novel Pd–Ru–Pd trinuclear complex. The trinuclear complex exhibited a prominent MLCT band because of the directional change in the MLCT processes showing a distinct color change from orange to dark-green.Figure optionsDownload full-size imageDownload as PowerPoint slide