Thermal,mechanical and spectral studies of some organic charge-transfer complexes

The thermal, mechanical and spectral properties of complex formed by picric acid with naphthalene and anthracene respectively have been studied using phase-diagram, linear velocity of solidification, degree of undercooling, fracture value, modulii of elasticity and IR, UV-visible spectral measurements. The phase-diagrams show that the 1:1 molecular complexes which are formed in these systems are stable in the solid state and remain intact in the molten state. The kinetics of solidification in both follows the Hilling and Turnbull equation and the observed kinetic data suggest the Winegard et al, mechanism for the solidification phenomena in the two complexes. The experimental and the theoretically calculated values of heats of fusion were compared. These properties of the pure components and the complexes were studied in the light of molecular interactions which play an important role in deciding the crystal structure of binary organic systems with the formation of congruent melting compounds having structures consisting of infinite stacks of alternate donor and acceptor molecules.