Ruthenium Complex Fragments as Constituents of Trinuclear Photoactive Supramolecular Assemblies Based on Hydrogen Bond Association

Abstract

The reaction of the octahedral complexes cis‐ or trans‐[Ru(C≡N‐tBu)4(CN)2], (Ru(CN)2), with the photochemically active [bis(bipyridyl)bibenzimidazole‐ruthenium(II)], (RubiH2), component via hydrogen bond association results in the formation of supramolecular aggregates with modified photophysical properties. The first structural characterization of a supramolecular adduct is reported, in which the N–H functions of the ruthenium bound bibenzimidazole ligand via hydrogen bonds serve as an interface directly toward a cyanide ligand acting as a bridge to another transition metal. In addition, the maximum stoichiometry of the supramolecular associates is estimated by NMR titration experiments and association constants of the hydrogen bonded adducts are determined by the decay of the emission intensity during the titration experiments.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Protonation‐Dependent Luminescence of an Iridium(III) Bibenzimidazole Chromophore

“…The same geometry could also be stated for the mononuclear iridium(III) complex presented in this work by comparison of the different bond lengths to the various ligands and the deviation of the angles from 180°[Ͻ(N5-Ir1-N4) 174.37(11)°, Ͻ(C38-Ir1- [2,10,29,30] The distances between the metal core and the bibenzimidazole ligand X-N BBI (X = Ru II or Ir III ) are depicted in Table 2. The bi(benz)imidazole ligand always exhibits longer distances to the metal core than the distances for the comparable ligands phenylpyridine or bipyridine.…”

“…[5,28,29] Here, the peripheral nitrogen atoms form twofold, complementary hydrogen bonds with two water molecules. The H-bond framework is capped by two molecules of dimethyl sulfoxide.…”

Functional Dimming of Pincer‐Shaped Bibenzimidazole‐Ruthenium(II) Complexes with Improved Anion‐Sensitive Luminescence

“…The general observation of hydrogen bonds with monodentate Hbond acceptors is peculiar, as previously reported structures of bibenzimidazole-ruthenium(II) complexes often show bifurcated H-bond frameworks with bidentate or multiple acceptors. [18,22,28,29] Scheme 2. Bibenzimidazole-ruthenium(II) complexes presented in this work; complexes K1 and K2 are pincer-shaped owing to anisyl substituents at the 4,4′-positions, and the latter is sterically confined.…”

A Macrocyclic 2,2′‐Bibenzimidazole Ruthenium(II) Chromophore as a Versatile Building Block for Supramolecular Devices

“…It is known from the literature that bibenzimidazoles undergo structural changes if bound to a metal center or to an organic backbone, that is, upon bending or twisting of the C2-C2Ј-bond. [19][20][21]30,34] To elucidate this effect in more detail, crystals of K1-H 2 were obtained in the presence of small amounts of water and propane-2-ol. Owing to the good quality of the data obtained, the location of the protons in the hydrogen-bond framework could be accurately identified (Figure 3, top).…”

“…[18] Particularly interesting ligands for such chromophores are 2,2Ј-bibenzimidazoles. [19][20][21][22][23][24][25][26][27] In contrast to systems based on 2,2Ј-bipyridine and 1,10-phenanthroline, 2,2Ј-bibenzimidazoles can bind a second metal center through co-ordination after deprotonation or in their protonated form bind anions through hydrogen bonding. [28] These effects influence the photophysical properties of the ruthenium chromophore, which can lead to cation-driven molecular light switches [29] and luminescent cation and anion sensors.…”