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Abstract: DABCO mono-betaine (1,4-diazabicyclo[2.2.2]octane-1-acetate) forms a complex with HCl and water in the ratio 2:3:2. The crystals are triclinic, space group P . Two non-equivalent molecules of protonated DABCO mono-betaines form a homoconjugated cation through the short and asymmetric O·H·O hydrogen bond of 2.470(3)Å. Two chloride anions are involved in the N–H···Cl hydrogen bonds of 3.049(2) and 3.023(3)Å. The third chloride anion is solvated by the water molecules. The molecules of bis(1,4-diazoniumbicyclo[2.2.2]octane-1-acetate) trihydrochloride dihydrate are linked into comb-like chains by the hydrogen bond formed between water molecules of the neighboring complexes; the O(W)–H···O(W) distance is 2.920(5)Å. FTIR spectrum shows several broad bands attributed to the νO–H, νN–H and νO·H·O vibrations. The structure of three bis(1,4-diazoniumbicyclo[2.2.2]octane-1-acetate) hydrochlorides are optimized at the B3LYP/6-31G(d,p) level of theory and a theoretical IR spectrum is calculated. The values of pK a of DABCO, DABCO mono- and di-betaines are determined by the potentiometric titration of their hydrohalides. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]