Dynamics and thermochemistry of the negatively charged clusters in a 2-hydroxyethylhydrazinium nitrate ionic liquid system.

The formation and fragmentation of negatively charged 2-hydroxyethylhydrazinium nitrate ([HOCHCHNHNH]NO, HEHN) ionic liquid clusters were examined using a guided-ion beam tandem mass spectrometer furnished with collision-induced dissociation of selected ions with Xe atoms. Measurements included the compositions of cluster ions formed in the ionization source, and the dissociation products, cross sections, and 0 K threshold energies for individually selected cluster ions. To identify the structures of the main cluster ion series [(HEHN)(HNO)NO] formed, molecular dynamics simulations were employed to create initial geometry guesses, followed by optimization at the ωB97XD/6-31+G(d,p) level of theory, from which global minimum structures were identified for reaction thermodynamics analyses. A comparison was made between the cluster formation and fragmentation in the negatively charged 2-hydroxyethylhydrazinium nitrate with those in the positive mode (reported by W. Zhou , , 2023, , 17370). In both modes, the cluster ions were predominantly composed of / below 350; loss of a neutral 2-hydroxyethylhydrazinium nitrate ion pair represents the most important cluster fragmentation pathway, followed by intra-ion pair proton transfer-mediated 2-hydroxyethylhydrazine and HNO elimination; and all clusters started to dissociate at threshold energies less than 1.5 eV. The overwhelming similarities in the formation and fragmentation chemistry of positively negatively charged 2-hydroxyethylhydrazinium nitrate clusters may be attributed to their inherent ionic nature and high electric conductivities.