Temperature-induced reversible structural phase transition of 1,4-dimethyl-1,4-diazabicyclo[2.2.2]octane bis(perchlorate)

1,4-Dimethyl-1,4-diazabicyclo[2.2.2]octane bis(perchlorate), C 8 H 18 N 2 2+ ·2ClO 4 − , was synthesized and separated as colorless rodlike crystals. Differential scanning calorimetry (DSC) measurements revealed that this compound underwent a reversible phase transition at ca. 201.7 K with a hystere...

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Bibliographic Details
Published in:RSC advances 2015-01, Vol.5 (69), p.55914-55919
Main Authors: Chen, Li-Zhuang, Cao, Xing-Xing, Huang, Deng-Deng, Pan, Qi-Jian
Format: Article
Language:English
Subjects:
Broken symmetry
Crystals
Differential scanning calorimetry
Diffraction
Order disorder
Phase transformations
Twisting
X-rays
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Summary:1,4-Dimethyl-1,4-diazabicyclo[2.2.2]octane bis(perchlorate), C 8 H 18 N 2 2+ ·2ClO 4 − , was synthesized and separated as colorless rodlike crystals. Differential scanning calorimetry (DSC) measurements revealed that this compound underwent a reversible phase transition at ca. 201.7 K with a hysteresis of 5.1 K width, which was also confirmed by dielectric measurements. Single crystal X-ray diffraction data suggested that there was a transition from a room temperature phase with the space group of Pnma ( a = 15.5417(14) Å, b = 13.3677(12) Å, c = 20.7728(19) Å, V = 4315.7(7) Å 3 and Z = 12) to a low temperature one with a space group of P 2 1 / n ( a = 13.331(3) Å, b = 15.185(4) Å, c = 20.477(5) Å, β = 90.895(3)°, V = 4144.8(17) Å 3 and Z = 12), and symmetry breaking occurred with an Aizu notation of mmmF 2/ m . The order–disorder transition of ClO 4 − anions and the ordering of twisting motions of the dabco ring may drive the phase transition.
ISSN:2046-2069
2046-2069
DOI:10.1039/C5RA07526B