The coordination chemistry of the new pyridine-based, N 2S 2-donating 12-membered macrocycle 2,8-dithia-5-aza-2,6-pyridinophane (L 1) towards Cu II, Zn II, Cd II, Hg II, and Pb II has been investigated both in aqueous solution and in the solid state. The protonation constants for L 1 and stability constants with the aforementioned metal ions have been determined potentiometrically and compared with those of ligand L 2, which contains a N-aminopropyl side arm. The measured values show that Hg II in water has the highest affinity for both ligands followed by Cu II, Cd II, Pb II, and Zn II. For each metal ion considered, 1 : 1 complexes with L 1 have also been isolated in the solid state, those of Cu II and Zn II having also been characterised by X-ray crystallography. In both complexes L 1 adopts a folded conformation and the coordination environments around the two metal centres are very similar: four positions of a distorted octahedral coordination sphere are occupied by the donor atoms of the macrocyclic ligand, and the two mutually cis-positions unoccupied by L 1 accommodate monodentate NO 3 - ligands. The macrocycle L 1 has then been functionalised with different fluorogenic subunits. In particular, the N-dansylamidopropyl (L 3), N-(9-anthracenyl)methyl (L 4), and N-(8-hydroxy-2-quinolinyl)methyl (L 5) pendant arm derivatives of L 1 have been synthesised and their optical response to the above mentioned metal ions investigated in MeCN/H 2O (4 : 1 v/v) solutions.