Synthesis, optical and thermal behaviour of palladium(II) complexes with 4-(4-alkoxy-2-hydroxybenzylideneamino)azobenzene

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• 作者：BOON-TECK HENG (1)
  GUAN-YEOW YEAP (1)
  DAISUKE TAKEUCHI (2)
  
• 关键词：Pd(II) complexes ; smectic A ; nematic ; 1H ; NMR ; Cu(II) complexes
• 刊名：Journal of Chemical Sciences
• 出版年：2013
• 出版时间：November 2013
• 年：2013
• 卷：125
• 期：6
• 页码：1435-1443
• 全文大小：577 KB
• 作者单位：BOON-TECK HENG (1)
  GUAN-YEOW YEAP (1)
  DAISUKE TAKEUCHI (2)
  
  1. Liquid Crystal Research Laboratory, School of Chemical Sciences, Universiti Sains Malaysia, 11800, Minden, Penang, Malaysia
  2. Chemical Resources Laboratory (Mailbox R1-03), Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan
  
• ISSN：0973-7103

文摘

A series of new Pd(II) complexes derived from the reaction of palladium acetate with 4-(4-alkoxy-2-hydroxybenzylideneamino)azobenzene having the flexible terminal chain of OC n H2n--, in which n are even numbers ranging from 8 to 16, has been successfully synthesized. The physical measurement and spectroscopic techniques (FTIR and 1H-NMR) reveal that the Pd(II) complexes possess the Pd–N and Pd–O coordination modes in which the central Pd(II) adopts square-planar geometry. The observation under the polarized light shows that all the ligands and Pd(II) complexes exhibit enantiotropic mesophases. The ligands with n-octyloxy and n-decyloxy flexible chains exhibit the nematic (N) and smectic A (SmA) phases whilst the Pd(II) complexes show exclusive SmA phase. The SmA phase observed in Pd(II) complexes can be supported by the presence of focal conic fan-shaped texture with the presence of curved lines which are prominent during the cooling process. On the other hand, the comparison studies show that Pd(II) complexes possess exceptional higher phase transition temperatures as compared to the corresponding Cu(II) and Ni(II) complexes. Graphical Abstract A new series of Pd(II) complexes with azobenzene core have been synthesized and characterized. The ligands with n-octyloxy and n-decyloxy flexible chains exhibit the nematic (N) and smectic A (SmA) phases whilst the Pd(II) complexes show exclusive SmA phase. Comparison study shows that Pd(II) complexes have exceptional higher phase transition temperatures as compared to its counterparts of Cu(II) and Ni(II).