Synthesis and physico-chemical properties of a novel series of aromatic electron acceptors based on N-heterocycles

The synthesis of a novel series of N-based heterocyclic salts using a simple and efficient N-alkylation of 1,2-bis(4-pyridyl)ethane with reactive halides is reported. These compounds can be transformed into the corresponding pyridinium methylides by addition of a base. The former exhibit an unstable absorption bands at 395-410 nm. The structures of the salts were fully characterized by UV-vis, IR, NMR and MS spectroscopy and elemental analysis. The pK values of selected compounds were also determined and the acid-basic equilibrium was investigated by UV-vis spectrophotometry. The thermal stability of all species was determined by thermogravimetric analysis.