Thermochemical properties of 1,2,3,4-tetraphenylnaphthalene and 1,3,5-triphenylbenzene in crystalline and liquid states studied by solution and fast scanning calorimetry

Abstract

Significant deviations were found between the solution enthalpy in benzene at 298.15 K and the fusion enthalpy at the melting temperature of 1,2,3,4-tetraphenylnaphthalene (3.9 ± 0.5 kJ mol−1 and 23.6 ± 0.6 kJ mol−1 (470.8 K), respectively) and 1,3,5-triphenylbenzene (20.1 ± 0.2 kJ mol−1 and 32.4 ± 1.2 kJ mol−1 (447.3 K)). These aromatic compounds are structurally related to benzene and their solution enthalpies in hypothetical liquid state at 298.15 K in benzene should be close to zero, so the differences between the solution enthalpy of crystal and the fusion enthalpy at the melting temperature should be attributed to the temperature dependence of the fusion enthalpy.Direct adjustment of the fusion enthalpy to 298.15 K requires knowledge of the supercooled liquid state heat capacity, which is hardly attainable by conventional methods due to fast crystallization. The heat capacities of 1,2,3,4-tetraphenylnaphthalene and 1,3,5-triphenylbenzene in liquid, deeply supercooled liquid, glassy and crystalline states were obtained for the first time by using fast scanning calorimetry in wide temperature ranges. Crystalline 1,2,3,4-tetraphenylnaphthalene heat capacity was measured over the temperature range from 323 to 410 K by conventional DSC. The temperature dependences of the heat capacities of the studied compounds in supercooled liquid state were fitted with the linear equations. The experimental results obtained by fast scanning calorimetry are in excellent agreement with the data obtained by solution calorimetry and conventional DSC.