Ruthenium(II) complexes of oligo(bipyridine-phenyl triazole)s were synthesized as receptors for anions. The receptors, which are partially preorganized through metal-ligand interactions, can fold into a helical conformation to bind chloride, bromide, iodide, or nitrate anions in their inner cavities in acetone or competitive H-bonding media such as 5% water in acetone and DMSO. The short oligomer 1 can sandwich the studied anions with high affinity in acetone. Addition of 5% water to acetone results in overall decreases in the binding strength due to the binding competition from water, but does not change the basic binding mode. The highly competitive H-bonding solvent DMSO causes the receptor-anion interactions to become even weaker. However, in DMSO, the short receptor 1 is still able to bind the halide anions with moderate affinities in a 1:1 stoichiometry, whereas the longer oligomer 2 forms double-strand helices with an anion wrapped inside for all anions investigated so far.
1.Beijing Normal Univ, Coll Chem, Key Lab Theoret & Computat Photochem, Minist Educ, Beijing 100875, Peoples R China 2.Beijing Normal Univ, Coll Chem, Key Lab Radiopharmaceut, Minist Educ, Beijing 100875, Peoples R China 3.Chinese Acad Sci, Inst Chem, Beijing 100190, Peoples R China 4.Univ Chinese Acad Sci, Beijing 100049, Peoples R China