Bis(2-pyridylmethyl)alkyl(thioalkyl)diamines as promising scaffolds for the construction of fluorescent and redox chemosensors for transition and post-transition metal ions

N,N′-Bis(2-pyridylmethyl)propylendiamine (1) and N,N′-bis(2-pyridylmethyl)-1,5-diamino-3-thiapentane (2) have been functionalised at the secondary nitrogen atoms with dansylamidoethyl (L1, L3), 2-quinolinylmethyl (L2, L4) and ferrocenylmethyl (L6, L7) pendant arms with the intention to study their potentiality as receptor units in molecular sensors. The optical response of L1–L4 to the presence of the metal ions Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ has been investigated in MeCN/H2O (4:1 v/v) solution. The electrochemical response of L6 and L7 to the presence of the same metal ions has been investigated in anhydrous MeCN/CH2Cl2 10:1 (v/v) solution. Results are compared and discussed with the aim to clarify the mutual role played by the bis(2-methylpyridyl)alkyl(thioalkyl)diamines and the signalling units attached to them in reaching the selectivity of the responses observed.