The phase diagram of a binary organic system involving diphenyl and succinonitrile shows the formation of a eutectic (0-968 mole fraction of succinonitrile) and a monotectic (0.074 mole fraction of succinonitrile) with a large miscibility gap in the system, the upper consolute temperature being 53-5°C above the monotectic horizontal. From the enthalpy of fusion of the pure components, the eutectic and the monotectic, determined by the DSC method, the enthalpy of mixing, Jackson's roughness parameter, interracial energy, size of the critical nudeus and excess thermodynamic functions were calculated.

Phase diagrams of N ,N-dimethylaminobenzaldehyde (DMAB)-anthranilic acid (AA) and 2-(4-(dimethylamino)benzylideneamino)benzoic acid (DMABAB)p-nitroaniline (PNA) systems, determined by the thaw-melt method, give two eutectics and a 1:1 intermolecular compound (IMC) in each case. Appropriate amounts (10 g) of each of the eutectics and the IMCs were prepared by a green synthetic method involving a solid state reaction without any solvent. These materials were characterized by X-ray diffraction, thermal and spectral methods and the optical properties of the pure components and the IMCs were studied. While negative values of heat of mixing in the case of a DMAB-AA system suggest clustering of molecules in both eutectic melts, those of positive value in E 1 and negative value in E 2 of the DMABAB-PNA system indicate the formation of a quasi-eutectic structure in E 1 melt and clustering of molecules in E 2 melt. The IMC of DMAB-AA system shows strong dual emission with two λ max one at 380 nm and the second at 450 nm with a total quantum efficiency of 0.49. The IMC of DMABAB-PNA system also shows a similar observation with two λ max one at 390 nm and second at 435 nm with a total quantum efficiency of 0.31.