Charge-transfer complexes formed in the reaction of 1,4,7,10-tetraazacyclododecane with π-electron acceptors

The reactions of the electron donor 1,4,7,10-tetraazacyclododecane (TACDD) with the pi-electron acceptors 7,7,8,8-tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL) and 2,4,4,6-tetrabromo-2, 5-cyclohexadienone (TBCHD) were studied spectrophotometrically in chloroform at room temperature. The electronic and infrared spectra of the formed molecular charge-transfer (CT) complexes were recorded. The obtained results showed that the stoichiometries of the reactions are fixed and depend on the nature of both the donor and the acceptor. Based on the obtained data, the formed charge-transfer complexes were formulated as [(Donor)(Acceptor)(2)] for the donor (TACDD) and the acceptors TCNQ TCNE, DDQ CHL and TBCHD. These CT-complexes were isolated as solids and have been characterized through electronic and infrared spectra as well as elemental and thermal analysis measurements. The formation constants (K-CT), charge transfer energy (E-CT), molar extinction coefficients (epsilon(CT)), free energy change Delta G(0), ionization potential Ip and oscillator strength f of the formed CT-complexes were obtained. (C) 2013 Elsevier B.V. All rights reserved.