UV-Vis, IR spectra and thermal studies of charge transfer complexes formed in the reaction of 4-benzylpiperidine with sigma- and pi-electron acceptors
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abstract
The reactions of the electron donor 4-benzylpiperidine (4BP) with the -acceptor iodine and -acceptors 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 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. Based on the obtained data, the charge-transfer complexes were formulated as [(4BP)I]+I3-, [(4BP)(DDQ)2], and [(4BP)(TBCHD)] for the donor (4BP) and the acceptors I2, DDQ and TBCHD. In the 4BP-TCNQ reaction, a short-lived CT complex is formed followed by rapid N-substitution by TCNQ forming the final reaction product 7,7,8-tricyano-8-benzylpiperidinylquinodimethane [TCBPQDM]. These products were isolated as solids and have been characterized through electronic and infrared spectra as well as elemental and thermal analysis measurements. The formation constants (KCT), charge transfer energy (ECT), molar extinction coefficients (CT), free energy change G and ionization potential IP of the formed CT-complexes [(4BP)I]+I3-, [(4BP)(DDQ)2] and [(4BP)(TBCHD)] were obtained. 2013 Elsevier B.V. All rights reserved.
