The conformational analysis of flexible 5,5'-bi(1H-1,2,4-triazole) mol
ecule containing various reaction centers has been performed by the se
miempirical methods MNDO,AM1 and PM3, and the internal rotation barrie
r calculated. The most stable conformation of the molecule has been de
termined to be the planar trans conformation. According to the three m
ethods, 5,5'-bi(1H-1,2,4-triazole) molecule (C) has been found to be r
elatively more stable than its tautomer 3,3'-bi(1H-1,2,4-triazole) (B)
and to be less stable than its other tautomer 3,3'-bi(4H-1,2,4-triazo
le) (A), Moreover, the electronic properties of 5,5'-bi(1H-1,2,4-triaz
ole) molecule and the effect of conformational changing on electronic
and geometric properties have also been investigated. To determine the
protonation sites of the 5,5'-bitriazole system, the molecular electr
ostatic poential (MESP) of the molecule has been calculated. The elect
ronic properties and conformations of the monoprotonated species forme
d from the protonation of the molecule have also been studied using AM
1 and PM3 routes. The proton affinity of the 5,5'-bitriazole molecule
has been calculated for the different nitrogens using AM1 and PM3 meth
ods and the possible protonation centers have been determined. The ele
ctronic properties and the geometry of Fe2+ complex of the bitriazole
system have been investigated by ZINDO/1 method and its formation proc
ess has been searched theoretically According to proton affinity value
s, the complex formation ability of A, B and C tautomers of bi(1,2,4-t
riazole) system have been evaluated and the stabilities of their Fe2complexes have been determined by ZINDO/1 route. It has been found tha
t tautomer B has a higher complex formation ability and forms more sta
ble metal complexes relative to the other tautomers.