One-Pot Synthesis and Redox Properties of Conjugation-Extended 4,4′-Bipyridines and Related Compounds. New Ligands Consisting of a Heterocyclic Three-Ring Assembly

Abstract

Dipyridyl-substituted heterocycles such as 2,5-di(4-pyridyl)thiophene 3, 2,5-di(4-pyridyl)furan 4, 2,5-di(4-pyridyl)thieno[3,2-b]thiophene 7, 1,4-di(4-pyridyl)benzene 6, 2,5-di(2-pyridyl)thiophene 8, and 2,5-di(3-pyridyl)thiophene 9 have been efficiently synthesized by a simple one-pot procedure through the palladium-mediated cross-coupling reaction between (trimethylstannyl)pyridines and dibromo-substituted heteroaromatics. The spectroscopic data (IR, ¹H NMR, ¹³C NMR, UV) as well as their reduction potentials of these compounds have been determined to evaluate the utility potentials to chelating ligands for metal complexes or to synthetic precursors of viologen-type bipyridinium salts. The conjugation interaction throughout the three rings appears to be more significant in 3 and 4 than in 6. The formation of stable redical anions and dianions of 3 and 4 has been proved by cyclic voltammetry.