Charge-transfer complexes of 4-methylpiperidine with σ- and π-acceptors

The solid charge-transfer (CT) molecular complexes formed in the reaction of the electron donor 4-methylpiperidine (4MP) with the sigma-electron acceptor iodine and pi-acceptors 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TBCHD) have been investigated spectrophotometrically in chloroform at 25 degrees C. These were characterized through electronic and infrared spectra as well as elemental and thermal analysis. The obtained results showed that the formed solid CT-complexes have the formulas [(4MP) I]I-+(3)-, [(4MP)(DDQ)(2)] and [(4MP)(TBCHD)] and with TCNQ the adduct [TCMPQDM] is obtained through N-substitution reaction in full agreement with the known reaction stoichiometries in solution as well as the elemental measurements. The formation constant K-CT, molar extinction coefficient epsilon(CT), free energy change Delta G(0), CT energy E-CT and the ionization potential I-p have been calculated for the CT-complexes [(4MP) I]I-+(3)-, [(4MP)(DDQ)(2)] and [(4MP)(TBCHD)]. (C) 2014 Elsevier B.V. All rights reserved.