Study of Donor-Acceptor Complexes by Ultrasonic Technique

Heterocyclic aromatic molecules can act as π-electron donors as well as n-electron donors. Heterocyclic molecules are therefore expected to form relatively more stable complexes with Iodine than homocyclic aromatic hydrocarbons. In order to establish this, the ultrasonic studies are carried out in n-hexane solutions containing iodine-thiophene system and iodine-pyridine system at 303 K. Ultrasonic velocities (U), densities (ρ), viscosities (ν) are measured for the two ternary systems containing equimolar amounts of iodine (acceptor) and heterocyclic aromatic hydrocarbon (donor). The acoustical and thermodynamical parameters are calculated. These values suggest that the donor-acceptor complexes are formed and they are thermodynamically stable.