Characterizing the thermal degradation mechanism of two bisphosphoramidates by TGA, DSC, mass spectrometry and first-principle theoretical protocols

The present investigation describes a combined experimental-theoretical strategy to assess the thermal resistance features of two symmetric bisphosphoramidates, tetraphenyl ethane-1,2-diylbis (phosphoramidate) 1 and tetraphenyl propane-1,3-diylbis (phosphoramidate) 5. Therefore, their structural reluctance to thermal decomposition through differential scan calorimetric (DSC) and thermogravimetric (TGA) experiments was evaluated. Then, their molecular degradation path was followed by analysing recorded data from mass spectrometry measurements performed at different temperature conditions. Their corresponding thermal degradation mechanism was then established by searching plausible transition states interconnecting the intermediaries found in our mass spectrometry records using a quantum theoretical protocol based on Coupled-Cluster calculations. Through this strategy, key intermediaries of the two bisphosphoramidates studied during their molecular degradation mechanism were identified, although compound 5 displayed the highest resistance to heat decomposition.