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Proton‐Induced Tuning of Metal–Metal Communication in Rack‐Type Dinuclear Ru Complexes Containing Benzimidazolyl Moieties
Author(s) -
Kobayashi Katsuaki,
Ishikubo Masamichi,
Kanaizuka Katsuhiko,
Kosuge Keiko,
Masaoka Shigeyuki,
Sakai Ken,
Nozaki Koichi,
Haga Masaaki
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201100074
Subject(s) - deprotonation , protonation , chemistry , metal , ferrocene , ligand (biochemistry) , crystallography , proton , ruthenium , stereochemistry , benzimidazole , electron transfer , photochemistry , medicinal chemistry , ion , receptor , organic chemistry , catalysis , electrochemistry , biochemistry , physics , electrode , quantum mechanics
Ru complexes bearing a bis‐tridentate benzimidazolyl ligand have been synthesized. The dinuclear ones act as a bibasic acid with p K a1 =4.36 and p K a2 =5.90. The protonated form of the dinuclear complex exhibited two one‐electron oxidations at +0.91 and +1.02 V versus the ferrocenium/ferrocene (Fc/Fc + ) couple (the potential difference (Δ E )=0.11 V), but the di‐deprotonated form showed two waves at +0.50 and +0.58 V versus Fc/Fc + (Δ E =0.08 V). Since the potential difference between two waves reflects the strength of the metal–metal interaction, the deprotonation of the benzimidazole moieties in the complexes weakened the Ru–Ru communication. The degree of electronic coupling between two metal centers, estimated from the intervalence charge transfer (IVCT) band, was greater for the protonated form. DFT calculations for the protonated and deprotonated forms of the dinuclear complex suggest that the Ru II – L (H 2 ) π* interaction plays a key role in the Ru–Ru interaction.