The patterns adopted in the solid state structures of over 300 cyclic NH carboximides as determined by X-ray diffraction are reviewed. While the analysis shows that the majority of these fit into just a few common patterns, a significant number exhibit more complex and interesting patterns involving the other functional groups present in addition to the cyclic imide.

The X-ray structure of the title compound has been determined for the first time. Data on its 1H–13C-NMR coupling constants and 15N-NMR spectrum are also given.

A synchrotron based photoionization spectrum represents a considerable improvement in resolution over early He(I) and He(II) spectra. The spectral onset shows a complex profile where two states, later shown to be the 12B2 and 12B1 states, are strongly overlapping. Symmetry-adapted coupled cluster calculations of the ionic state sequence up to 27 eV, give the sequence of state vertical ionization energies (VIE) as: 12B2 < 12B1 < 12A2 < 12A1 < 22B1 < 32B1 < others. Density functional calculations of the corresponding adiabatic terms (AIE) were also performed using the long range-corrected version of the Becke three-parameter hybrid functional (B3LYP), through the Coulomb-attenuating method (CAM-B3LYP) functional. Complete active space self-consistent field (CASSCF) methods were used to determine the wave-functions for the 22B1 and 32B1 states. Selected ionic state vibrational profiles, including all p-ionizations, were interpreted by Franck-Condon (FC) procedures, and compared with experiment for the above group of states. Although the lowest IE shows considerable overlap of the 12B2 and 12B1 states, there is no apparent vibrational interference between the two states. This is in marked contrast to our previous work on the halogeno-benzenes, where overlapping state envelopes led to degradation of the higher energy states, which showed considerable widening of the line-width at half-height.

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Thirteen new crystal structures of cyclic NH carboximides have been determined and are compared with respect to the mode of intermolecular hydrogen bonding observed in the crystal. The structures include a new cyclobutane-fused succinimide, seven new simple bi- and tricyclic succinimides derived from Diels–Alder reactions of maleimide, three methylated glutarimides, a morpholinedione and adipimide, the first seven-membered ring NH carboximide to be structurally characterised. Overall, seven of the compounds adopt a ribbon structure, five show centrosymmetric dimers, and one has bonding between NH and a remote bridging ether oxygen. Halogen bonding was also detected in one case.