The synthesis of some macrocyclic compounds based on 1,8-naphthyridine and 1,10-phenanthroline with rings containing four and five oxygen atoms is reported. These compounds were tested for cation selectivity in poly(vinyl chloride)-based potentiometric sensors. Nernstian esponse was observed towards the potassium ion but with low discrimination for potassium in the presence of other cations. Dimethyl 4-octyloxy-1,10-phenanthroline-2,9-dicarboxylate, a precursor to one of the macrocyclic series, showed a high preference for divalent cations such as Zn2+, Ba2+, Cu2+ and Co2+. .