Charge-transfer complexes of 1-(2-aminoethyl) piperazine with σ- and π-acceptors

The solid charge-transfer (CT) molecular complexes formed in the reaction of 1-(2-aminoethyl) piperazine (AEPIP) with the σ-acceptor iodine and π-acceptors 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 7,7,8,8-tetracyanoquinodi-methane (TCNQ), 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TBCHD) and 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL) were studied in chloroform at 25 °C. The products were investigated through electronic and infrared spectra as well as elemental analysis. The obtained results showed that the formed solid CT-complexes have the formulas [(AEPIP) I]+ I 5 - , [(AEPIP)(DDQ)2], [(AEPIP)(TCNQ)2], [(AEPIP)2(TBCHD)3] and [(AEPIP)(CHL)] which are in full agreement with the known reaction stoichiometries in solution as well as the elemental analysis measurements. The formation constant KCT, molar extinction coefficient εCT, free energy change ΔG0 and CT energy ECT have been calculated for the CT-complexes [(AEPIP)(DDQ)2], [(AEPIP)(TCNQ)2] and [(AEPIP)(CHL)] as well.