Charge-transfer complexes formed in the reaction of 2-amino-4-ethylpyridine with π-electron acceptors

Molecular charge-transfer complexes (CT) of electron donor 2-amino-4-ethylpyridine (2A4EPy) with π-acceptors tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TBCHD) have been studied spectrophotometrically in chloroform at 25 °C. These were investigated through electronic, infrared, mass spectra and thermal measurements as well as elemental analysis. All formed complexes exhibit well resolved charge-transfer bands in the regions where neither donor nor acceptors have any absorption. The obtained results show that the formed solid CT-complexes have the structures [(2A4EPy)(TCNE)2], [(2A4EPy)2(DDQ)] and [(2A4EPy)2(TBCHD)] for 2-amino-4-ethylpyridine in full agreement with the known reaction stoichiometries in solution as well as the elemental measurements. The formation constant KCT, molar extinction coefficient εC.T, free energy change ΔG0, CT energy ECT, ionization potential Ip and oscillator strength ƒ have been calculated for these three CT-complexes