synthesis and characterization of azo compounds and study of the effect of substituents on their liquid crystalline behavior含氮的化合物的合成和表征和研究取代基对其液体结晶行为的影响.pdf

Molecules 2010, 15, 5620-5628; doi:10.3390/molecule OPEN ACCESS molecules ISSN 1420-3049 /journal/molecules Article Synthesis and Characterization of Azo Compounds and Study of the Effect of Substituents on Their Liquid Crystalline Behavior Uhood J. Al-Hamdani *, Tarik E. Gassim and Howraa H. Radhy Department of Chemistry, College of Education, Basrah University, Basrah, Iraq ∗ Author to whom correspondence should be addressed; E-Mail:Uhood1959@; Tel.: +9647712616545. Received: 1 July 2010; in revised form: 4 August 2010 / Accepted: 12 August 2010 / Published: 13 August 2010 Abstract: In this paper we present six select mesomorphic azo compounds distinguished by the presence of diverse substituents on a central benzene nucleus. All the synthesized compounds exhibit enantiotropic mesophases. The mesomorphic properties of the substituted compounds were compared with those of the unsubstituted parent compound to evaluate the effect of the nature and position of the substituents on mesomorphism. Keywords: azo; lateral group; liquid crystal Introduction Until 1983 it was generally accepted that substituents diminish the mesogenic properties of a compound, with the extent of the effect depending on their size. Cox et al. [1] synthesized nematogens in which a phenyl side group was attached without a spacer. Mesogens with aromatic substituents have been prepared [2-7]. Recently a homologous series of mesogenic azo compounds containing three rings in t