DABCO mono-betaine hydrate studied by X-ray diffraction, DFT calculations and spectroscopic methods

A new DABCO mono-betaine (1-carboxymethyl-1,4-diazabicyclo[2.2.2]octane inner salt) has been synthesized. It crystallizes as monohydrate in orthorhombic space group Pmn21. The DABCO mono-betaine and water molecules are located on a mirror plane. The water molecules link DABCO mono-betaine into linear chains through the H–O–H⋯OOC and H–O–H⋯N hydrogen bonds of 2.709(2) and 2.875(2) Å. The structure of the title compound optimized at B3LYP/6-31G(d,p) level of theory is consistent with X-ray diffraction. The absorption bands in the FTIR spectrum have been assigned. The calculated magnetic isotropic shielding tensors confirm the assignments of the 13C NMR resonance signals.