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Theoretical Study of the Inter‐ionic Hydrogen Bonding in the GZT Molecular System
Author(s) -
Chen Cheng,
Liu MinHsien,
Cheng SouRo,
Wu LungShing
Publication year - 2003
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.200300108
Subject(s) - chemistry , hydrogen bond , ionic bonding , low barrier hydrogen bond , ion , crystallography , bond energy , hydrogen , molecule , computational chemistry , organic chemistry
Diguanidinium‐5,5′‐azotetrazolate (GZT) is an ionic type high energy compound, which is combined with two guanidinium cations (C(NH 2 ) 3 + or defined as G + ) and one 5,5′‐azotetrazolate‐2‐anion (ZT 2− ). The structure of ZT 2− is made up of two N 4 C tetrazole type five‐member rings connected by an azo type (‐N=N‐) linkage. The multi‐nitrogen structure of the compound makes the ZT 2− anion in the GZT molecular system a major high‐energy source with the properties of an electron donor. In addition to this, the C(NH 2 ) 3 + cation containing H atoms within its NH 2 groups behaves like a good charge acceptor not only for the formation of hydrogen bonds but also in regard to the stabilization effect within the whole molecular system. There are four strong inter‐ionic hydrogen bonds in this GZT molecular system combining with the ZT 2− anion and the two C(NH 2 ) 3 + (or G + ) cations. It is impossible to calculate hydrogen bond energy between its ions by a conventional energy difference method because it is difficult to distinguish whether such an energy difference happens simply because of inter‐ionic Coulomb attraction or because of the pure energy of the hydrogen bond. With our newly developed “hydrogen bonding localization analysis methods”, we have successfully calculated the localized hydrogen bond orders and energies of the inter‐ionic hydrogen bonds in the GZT molecular system. When the localized hydrogen bond energy, the bond order, the shortening of the hydrogen bond distance, the elongation of the bond length, and the red shift of stretching frequency of the closely related NH bond are compared in order to determine the hydrogen bonding strength, all the evidence taken together, proves that the four hydrogen bonds in the GZT inter‐ionic molecular system are stronger than most hydrogen bonds existing in all the inter‐molecular and intra‐molecular hydrogen‐bonding problems we have ever considered previously.