Discotic liquid crystals of transition metal complexes, 31: establishment of mesomorphism and thermochromism of bis[1,2-bis(4-n-alkoxyphenyl)ethane-1,2-dithiolene]nickel complexes

Two series of bis[1,2-bis(4-n-alkylphenyl)ethane-1,2-dithiolene]nickel, C-n -Ni (n = 1-12), and bis[1,2-bis(4-n-alkoxyphenyl)ethane-1,2-dithiolene]nick el, CnO-Ni(n = 1-12, 14, 16, 18), have been synthesized. Their mesomorphism , thermochromism, supramolecular structures and pi -acceptor property have been investigated by using different scanning calorimetry, polarizing micro scopy, temperature-dependent X-ray diffraction technique, electronic spectr oscopy and cyclic voltammetry. From the X-ray diffraction and electronic sp ectral results, it was established that the CnO-Ni complexes for n less tha n or equal to 10 exhibit two differently colored discotic lamellar (D-L) me sophases whereas none of the C-n-Ni complexes has a mesophase, and that the thermochromism (brown --> green) is attributable to a slow transformation from the Ni-Ni bonded dimers to the Ni-S bonded dimers.