Synthesis, characterization, crystal structure and liquid crystal studies of some symmetric naphthalene derivative molecules

Abstract

The synthesis of a series of symmetrical liquid crystals having naphthalene as the central rigid core and attached to long chain flexible 4′-alkoxybenzoate moiety at positions 2,6 - of the aromatic ring are reported. The mesophase behavior of the molecules was investigated using differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction studies. The studies reveal that the synthesized compounds exhibit stable enantiotropic mesophase of Smectic A (SmA) and Nematic (N) phase. The mesophase appearance is independent of the length of the alkyl chain. The molecular structure was determined by single crystal X-ray diffraction technique. The derivative with n-heptyloxy- flexible chain crystallizes under triclinic, P1¯space group with unit cell dimension a = 5.569(3) Å, b = 10.540(5) Å, c = 15.254(9) Å, α = 73.434(18)o, β = 80.807(19)o and γ = 82.02(2)o, V = 843.1(8) Å3. The dihedral angle between the naphthalene ring system and the benzoate moiety is 63.63(2)o.