The cation-binding properties of the title compounds (1)-(7) with the alkali, alkaline-earth, silver, ammonium and copper(II) picrates have been determined from host/guest complexation experiments. The association constants depend on the ligand cavity diameter, the nature of the heterocycle , the type and number of donor atoms and charge on the complexed cation. Dynamic 1H n.m.r . spectroscopy has also been employed, to demonstrate the comparable stability of a 21-membered 1,10-phenanthrolino ligand to its pyridine analogue in binding a benzylammonium salt. From this study, information on both the complex and ligand conformations was obtained.