STRUCTURES, ENERGETICS, AND REACTIONS OF PROTON-BOUND HYDRAZINE CLUSTERS

Proton bound hydrazine containing clusters were studied experimentally by a temperature- and pressure-variable ion source in conjunction wit h tandem mass spectrometry and computationally by semiempirical (PM3 a nd AM1) and ab initio (6-31G) methods. The series (N2H4H+ demonstrated a magic number at n = 4, confirmed by the dependences of metastable f ractions and average kinetic energy releases on cluster size. The sugg ested favored structure calculated for the tetramer has an N2H5+ core ion and three hydrazine molecules bound to the protonated nitrogen ato m, leaving two bare hydrogen atoms on the other nitrogen atom. Binding energies for solvent evaporation from (N2H4H+ were deduced computatio nally and by fitting of kinetic energy release distributions and using thermal kinetics in small systems. A series of magic numbers n+m = 5 were observed for mass spectra of (N2H4)(n)(H2OH+ (n = 1-6, m = 1-4). Two collisionally activated dissociation channels were observed for th ese mixed clusters-water loss for n+m less than or equal to 5 and hydr azine loss for n+m greater than or equal to 6-demonstrating a structur al transformation at n+m = 5. Additional cluster series (N2H4)(n)N2H6. +, (N2D4)(n)N2D5H.+, and (N2D4)(n)N2D6.+ were observed, which can have N(2)X(6)(.+) or N(4)X(10)(.+) (X = H or D) as core radical cations.