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|Title:||Crystal Structure and Phase Transition of Diglycine Perchlorate|
|Citation:||JOURNAL OF CHEMICAL CRYSTALLOGRAPHY,41(2)147-154|
|Abstract:||Diglycine perchlorate (DGPCl), a new 2:1 adduct formed between glycine and perchloric acid has been obtained and studied using differential scanning calorimetry and single crystal X-ray diffraction. DGPCl undergoes a reversible first-order phase transition at 261.5 K. The crystal structures at 150 and 293 K have been determined to be triclinic, space group PaEuro1, Z = 2, suggesting the first-order phase transition to be an isostructural phase transition. The DGPCl crystal consists of five glycinium-monoprotonated glycinium dimers and five perchlorate anions in an asymmetric unit. The glycine moieties in the glycinium-monoprotonated glycinium dimers are non-planar. Two types of hydrogen bonds are present in the crystal, strong O-H center dot center dot center dot O hydrogen bonds and a weak N-H center dot center dot center dot O hydrogen bonds. The short, strong O-H center dot center dot center dot O hydrogen bond connects the glycinium ion and mono protonated glycinium ion. In four of the dimers, the O-H and H center dot center dot center dot O bond lengths are different, indicating the hydrogen atom to be located more close to the monoprotonated glycinium ion. However, in one of the glycinium-monoprotonated glycinium dimer the O center dot center dot H and H center dot center dot O bond lengths are nearly equal, suggesting the hydrogen atom (O center dot center dot center dot H center dot center dot center dot O) to be attached to the oxygen atoms of both glycine moieties. On thermal transition some of these hydrogen bonds are weakened and in all dimers the hydrogen atom seems to be located more close to the mono protonated glycinium ion.|
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