Thermodynamic Properties of 1,1′,6,6′-Tetraaza-7,7′-bi(bicyclo[4.1.0]heptane) by Calorimetric and Quantum Chemical Methods

Experimental and quantum-chemical methods were used to determine the thermodynamic properties of one of the representatives of the 1,6-diazabicyclo[4.1.0]heptane molecular system which is of interest in design of new promising high-energy density materials. The combustion energy of this compound at 298.15 K was measured using isoperibolic macrocalorimeter with a static bomb. The enthalpy of sublimation was determined by Knudsen cell mass spectrometry method. The heat capacity in the range of 6–350 K was studied using vacuum adiabatic calorimetry. No phase transitions were found by analyzing the behavior of the heat capacity curve. It has been shown that purification of a substance by recrystallization can lead to encapsulation of the solvent inside the crystalline structure. Using high-level quantum chemical calculations, the enthalpy of formation and thermodynamic functions of this compound in the gas phase were obtained. When calculating thermodynamic functions, the conformational isomerism of the studied molecule was taken into account. As a result, a complete set of standard thermodynamic functions was obtained for the studied compound, including formation functions, both in the crystalline and gaseous phases over a wide temperature range.