Three one‐dimensional coordination polymers, [MnCl2(4‐pyterpy)]∙2CHCl3 (1), [Mn(NO3)2(4‐pyterpy)]∙CHCl3 (2) and [Ag(NO3)(3‐pyterpy)]∙H2O (3) (4‐pyterpy = 4′‐(4‐pyridyl)‐2,2′:6′,2″‐terpyridine and 3‐pyterpy = 4′‐(3‐pyridyl)‐2,2′:6′,2″‐terpyridine) were synthesized and characterized by X‐ray diffraction. All three compounds exhibit a rare “head‐to‐tail” coordination of the multidentate ligand, but differ significantly in their polymer chain conformations. Additionally, the fluorescent properties of all three compounds were investigated and show a weak, ligand‐centered fluorescence at 416–418 nm.

No abstract

In memory of Klaus Hafner 2-Aminobenzimidazole 10, although a weak catalyst in the monomeric state, is a successful building block for effective artificial ribonucleases. In an effort to identify new building blocks with improved catalytic potential, RNA cleavage by a variety of heterocyclic amidines and guanidines has been studied. In addition to pK a values and steric effects, the energy difference between tautomeric forms seems to be another important parameter for catalysis. This information is available from quantum chemical calculations on higher levels, but semiempirical methods are sufficient to get a first estimate. According to this assumption, imidazoimidazol 18, characterized by isoenergetic tautomeric forms, is superior to 2-aminoimidazol 6, the best candidate among the simple compounds. By far the largest effects are seen with 2-aminoperimidine 24, which rapidly cleaves RNA even in the micromolar concentration range. The impressive reactivity, however, is related to a tendency of compound 24 to form polycationic aggregates which are the actual catalysts.

Salts. Competing Hydrodebromination and SNAr Processes. -Fluorinated diphenyl ether systems are synthesized starting from 1,2-and 1,3-dibromotetrafluorobenzene with high regioselectivity. In contrast, 1,4-dibromotetrafluorobenzene (X) is less reactive and gives only low yields. -(BANKS, B.; CARGILL, M. R.; SANDFORD*, G.; TADEUSIAK, A. J.; WESTEMEIER, H.; YUFIT, D. S.; HOWARD, J. A. K.; KILICKIRAN, P.; NELLES, G.; J. Fluorine Chem. 131 (2010) 5, 627-634,