The synthesis of three new homoleptic trischelate ruthenium(ii) complexes bearing new 2,2'-bipyridine ligands, 5,5'-dibenzylamido-2,2'-bipyridine () and 5-benzylamido-2,2'-bipyridine (L1) has been achieved. In the case of [Ru(L2)(3)](2+), the mer and fac isomers have been separated. (1)H NMR spectroscopic anion binding studies indicate that the two C(3)-symmetric pockets provided by [Ru(L1)(3)](2+) is conducive to receive a range of anions, although this is not readily reflected in the photophysical behaviour. The fac-isomer of [Ru(L2)(3)](2+) does appear to have an enhancement in the binding interactions over the mer form with dihydrogenphosphate salts, although the difference is much less marked with the spherical chloride ions. From X-ray crystallographic evidence, the ability to hold water in the "anion" binding cleft can inhibit the strength of the interactions with anions, giving rise to the observed selectivity for directional oxoanions such as dihydrogen phosphate.

The synthesis of two new tripodal complexes [Ru(L3)](PF(6))(2) and [Ru(L4)](PF(6))(2), encapsulating a ruthenium(II) cation, has been successfully achieved and the products fully characterized, including by X-ray structural determination. The smaller cavity, built around a tris(2-aminoethyl)amido scaffold demonstrated only moderate and predictable interactions with a range of anions and no significant spectroscopic change with nitrate, chloride and bromide, although dihydrogen phosphate did result in an almost stoichiometric precipitation. The expansion of the cavity to include the more rigid 1,3,5-benzenetricarbonylamide group creates a larger cavity, which shows a decrease in the emission on the introduction of chloride, bromide, hydrogen sulfate and nitrate salts, with the (1)H NMR titrations giving a surprisingly high binding affinity for nitrate over the smaller and simpler halides.

Three thiourea ligands and their dirhenium(i) complexes are reported that show an unusual cooperative binding to two dihydrogenphosphate anions; this could explain the high selectivity for phosphate in many reported anion receptors.