A Sn-119 and Fe-57 Mossbauer Effect Study of the Crystalline Phase of 7S5

Abstract

The Mossbauer effect of Sn-119 and Fe-57 has been used to study solutions of trimethyltin-4-methoxybenzylidene-4′-aminocinnamate (4.3% by weight) and Fe-57 enriched 1-1′-diacetylferrocene (0.2% by weight) in the crystalline phase of the liquid crystalline material 4-n-pentylphenyl-4′-n-heptyloxythiobenzoate (7S5). A pronounced deviation from Debye-like behavior was observed at 180 K in the In (recoil-free fraction) vs temperature data for the tin-bearing probe molecule. This deviation may be interpreted as due to a crystal-crystal phase transition which has been observed at 183 K. For the iron-bearing probe molecule, no deviation from Debye behavior was found up to 300 K. The data of this report support the interpretation that the phase transition is due to a rotation of the 7S5 molecule about the C-S bond.