Ab initio study of the molecular structure and spectroscopic properties of tetraazatetracyclotridecane and tetrakis(dimethylamino)methane

The equilibrium structures of 1,4,7,10-tetraazatetracyclo[5.5.1.0^4,13.0^10,13]tridecane and tetrakis(dimetriylamino)methane were calculated at the HF/6-31G** ab initio level of theory and found to show a spiro-connection of two U- and W-shaped arrangements of the nitrogen lone pairs with D₂ and D_2d symmetry, respectively. The NMR ¹H and ¹³C chemical shifts have been analyzed with ab initio continuous set of gauge transformations (CSGT) calculations performed with the B3LYP/6-311+G(2d,p) hybrid functional model. The He(I) photoelectron spectra were measured and interpreted by means of ab initio outer valence Green function (OVGF) calculations, which give an overall consistent reproduction of the energies and splittings of the n(N) bands.