Mesomorphic behaviour, single crystal and low angle variable temperature X-ray diffraction studies of the chloro-bridged cyclopalladated dimer obtained from 4,4′-hexyloxyazobenzene
作者:
A. Crispini,
M. Ghedini,
S. Morrone,
D. Pucci,
O. Francescangeli,
期刊:
Liquid Crystals
(Taylor Available online 1996)
卷期:
Volume 20,
issue 1
页码: 67-76
ISSN:0267-8292
年代: 1996
DOI:10.1080/02678299608032028
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
The newly synthesized palladium complex [(Azo-6)Pd(μu-C1)]2,1, [H(Azo-6)= 4,4′-hexyloxyazobenzene] has been investigated by optical observations, calorimetric measurements, and single crystal and low angle variable temperature X-ray diffraction techniques. Two different mesophases appear from 210 to 220°C (nematic) and above 220 until 235°C (smectic E) where the compound eventually decomposes. The nematic phase is not in thermodynamic equilibrium and when subjected to an annealing process transforms into a smectic phase. The molecular structure of the dinuclear cyclopalladated complex1has an intramolecular Pd-Pd distance of 3.528(1) Å. Moreover the molecules of1are arranged in pairs with an intermolecular Pd-Pd non-bonded interaction distance of 3.668(1) Å. On the basis of this structural feature and of the variable temperature low-angleXRDstudies, transitions involving dissociation of the molecular pairs (e.g. N(pair)⇌E(single), on heating; N(pair)→SE(pair), at constant temperature) are suggested.
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