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Syntheses and Structures of Bis(4,4′‐t‐butyl‐2,2′‐bipyridine) Ruthenium(II) Complexes with functional Derivatives of Tetramethyl‐bibenzimidazole [(tbbpy)2RuCl2] reacts with dinitro‐tetramethylbibenzimidazole (A) in DMF to form the complex [(tbbpy)2Ru(A)](PF6)2 (1a) (tbbpy: bis(4,4′‐t‐butyl)‐2,2′bipyridine). Exchange of the two PF6− anions by a mixture of tetrafluor‐terephthalat/tetrafluor‐terephthalic acid results in the formation of 1b in which an extended hydrogen‐bonded network is formed. According to the 1H NMR spectra and X‐ray analyses of both 1a and 1b, the two nitro groups of the bibenzimidazole ligand are situated at the periphery of the complex in cis position to each other. Reduction of the nitro groups in 1a with SnCl2/HCl results in the corresponding diamino complex 2 which is a useful starting product for further functionalization reactions. Substitution of the two amino groups in 2 by bromide or iodide via Sandmeyer reaction results in the crystalline complexes [(tbbpy)2Ru(C)](PF6)2 and [(tbbpy)2Ru(D)](PF6)2 (C: dibromo‐tetrabibenzimidazole, D: diiodo‐tetrabibenzimidazole). Furthermore, 2 readily reacts with 4‐t‐butyl‐salicylaldehyde or pyridine‐2‐carbaldehyde under formation of the corresponding Schiff base RuII complexes 5 and 6. 1H NMR spectra show that the substituents (NH2, Br, I, azomethines) in 2 ‐ 6 are also situated in peripheral positions, cis to each other. The solid state structure of both 2, and 3, determined by X‐ray analyses confirm this structure. In addition, the X‐ray diffraction analyses of single crystals of the complexes [(tri‐t‐butyl‐terpy)(Cl)Ru(A)] (7) and [(A)PtCl2] (8) display also that the nitro groups in these complexes are in a cis‐arrangement.

Hydrogen bond association between ruthenium bibenzimidazole and carboxylated polypyridylosmium complexes results in stable supramolecular aggregates. The determined stability constant of logK ഠ 6 ± 0.3 allows efficient energy transfer from the ruthenium to the osmium moiety.

An emission study of the interaction between dihydrogen phosphate and a series of ruthenium polypyridyl complexes containing the anion receptor 4,4'-bis[(2-methoxyethyl)carbamoyl]-2,2'-bipyridine is reported. An increase of the emission intensity and lifetime are observed in the range 0-2.5 molar equivalents of H 2 PO 4 -. The effect of the addition of trace amounts of water is also examined.Graphical Abstract. the emission increases upon addition of the first 2.5 equivalents of dihydrogen phosphate, however, further increases lead to a decrease in both emission intensity and lifetime. The effect of the addition of trace amounts of water is also examined.