Azo isocyanide gold(i) liquid crystals, highly birefringent and photosensitive in the mesophase.
Isocyanide ligands bearing an azo group and one alkoxy chain OC(n)H(2n+1) have been synthesized. They are calamitic liquid crystals for n > 4 and display nematic (n = 8, 12) and SmA (n = 12) mesophases. Their gold(I) compounds [AuX(CNR)] (X = Cl, C(6)F(5); R = C(6)H(4)N horizontal lineNC(6)H(4)OC(n)H(2n+1), n = 4, 8, 12) have been obtained by displacement of a weakly coordinated ligand. The chloro gold(I) compounds exhibit nematic (n = 4) and SmA mesophases, and decompose at temperatures higher than 200 degrees C, before reaching the clearing point. The pentafluorophenyl gold(I) compounds show nematic and SmA (n = 12) mesophases. All the derivatives are photosensitive in solution because of trans to cis isomerization of the azo group under UV light, which reverts photochemically or thermally to the trans isomer. Irradiation in the mesophase also induces isomerization with consequent destabilization of the mesophase to an isotropic liquid; the mesophase is recovered as soon as illumination stops. These azo mesogens show high birefringence values, higher for the linear gold complexes than for the free azo ligand.
Arias
Javier
J
IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, 47011-Valladolid, Spain.
Bardají
Manuel
M
Espinet
Pablo
P
Folcia
César L
CL
Ortega
Josu
J
Etxebarría
Jesús
J