Molecular structure of 3,3-pentamethylenediaziridine in gas and solution phases

The equilibrium molecular structure of the 3,3-penta-methylenediaziridine (PMDA) molecule in the gas phase was determined by gas-phase electron diffraction in combination with quantum chemical calculations up to the CCSD(T)-AE/cc-pwCVQZ level and estimation of the mean amplitudes and anharmonic vibrational corrections using quadratic and cubic force fields. 1D and 2D ¹H and ¹³C NMR spectra of PMDA in a CDCl₃ solution recorded at different temperatures revealed the temperature dependence of the chemical shifts of NH protons. Nonempirical simulations of small PMDA clusters, carried out at the DFT-B3LYP/6-31++G(2d,p) level, enabled us to suggest an interpretation of the NMR data