Acoustical and spectroscopic investigation of charge transfer complexes of certain aromatic compounds with iodine in n-hexane at 303 K

Charge transfer complexes formed between iodine (acceptor) and six aromatic compounds, namely, benzene, pyrrole, thiophene, pyridine, quinoline and 2-methylquinoline (quinaldine) in n-hexane medium have been investigated by ultrasonic and UV-visible spectroscopic techniques at 303 K. The measured values of ultrasonic velocity, density and viscosity were used to compute acoustical parameters and excess thermodynamic parameters. The trend in acoustical parameters with concentration identifies the existence of strong interactions amongst the solutes and the sign and magnitude of excess parameters establish the possibility of complex formation between the solute molecules. The specific interaction between the solutes is identified through the UV-visible spectra using Benesi-Hildebrand theory. The formation constants (K) of the charge-transfer complexes were determined by the Benesi-Hildebrand equation (spectroscopic method) and compared with those obtained by Kannappan method (ultrasonic). The trend in K values obtained by ultrasonic and spectral methods is similar and is explained with the structures of the donor molecules. (c) 2014 Elsevier B.V. All Tights reserved.