Structure and liquid crystalline properties of 2-hydroxyazobenzenes. X-ray diffraction, infra-red and DFT theoretical studies

✍ Scribed by J Pająk; M Rospenk; Z Galewski; L Sobczyk

• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 245 KB
• Volume: 700
• Category: Article
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2003.11.056

✦ Synopsis

The family of 2 0 -hydroxy-4 0 -alkyloxyazobenzenes containing in position 4 either CH 3 or Cl group with varying number of carbon atoms in alkyl group was analysed from the point of view of liquid crystalline properties and intramolecular OH• • •N hydrogen bonding. The phase transition diagrams show that insertion of the OH group in 2 0 position leads to a marked extention of mesophases as compared with parent azobenzenes and appearance in addition to nematic of the smectic SmA phase in the case of 4-chloro-derivatives. The role of chelate conjugating OH• • •N hydrogen bonds in modification of mesophases is discussed based on DFT theoretical and X-ray as well as infrared studies. The importance of the molecule pairing is emphasized. Most important feature of mesophases and crystalline state of compounds under study is appearance of a continuous absorption down to 500 cm 21 which is absent in solutions and Ar matrices.