New -Conjugated Ferrocenyl-Substituted Heterocyclic Systems Containing Electron-Deficient Aromatic Nitrogen Heterocycles

A series of ferrocenyl-substituted methyl ketones and chalcones were synthesized and converted to unsymmetrical 4,6-disubstituted pyrimidin-2-amines and 2-(1H-pyrrol-1-yl)pyrimidines in which the ferrocene fragment is separated from the pyrimidine ring by π-deficient (pyridine) or π-excessive (thiophene) heterocycle. The forbidden band gap of the obtained compounds was determined on the basis of their UV spectra ($$E_{\text{g}}^{\text{opt}}$$Egopt = 1.75‒2.36 eV), and their electrochemical properties were studied. The presence of a thiophene ring between the ferrocene and pyrimidine fragments reduces the redox potential of the ferrocene fragment (20‒30 mV), whereas pyridine spacer between the ferrocene and pyrimidine fragment increases the redox potential of the ferrocene fragment by more than 100 mV.