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

• Published in: Journal of molecular structure Vol. 700; no. 1; pp. 191 - 197
• Main Authors: Pająk, J, Rospenk, M, Galewski, Z, Sobczyk, L
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.08.2004
• Subjects: 2-Hydroxyazobenzenes; DFT calculation; Infra-red; Intramolecular OH⋯N hydrogen bonding; X-ray diffraction; X-ray diffraction; DFT calculation; Infra-red; Intramolecular OH⋯N hydrogen bonding; 2-Hydroxyazobenzenes
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2003.11.056

The family of 2′-hydroxy-4′-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′ 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 −1 which is absent in solutions and Ar matrices.