Discotic liquid crystals of transition metal complexes 25: influence of the central metal on columnar mesomorphism and π-acceptor properties of the octa-alkoxy-substituted bis(diphenyldithiolene)metal complexes

Abstract In order to investigate the influence of the central metal on mesomorphism and π-acceptor properties of the octa-alkoxy-substituted metal complexes, novel homologs, bis[di( n -alkoxy)phenyldithiolene]palladium and bis[di( n -alkoxy)phenyldithiolene]platinum ( n -alkoxy=C n H 2 n +1 O, n =1 to 12), have been synthesized. The mesophases were established by microscopic observations, DSC, and temperature-dependent X-ray diffraction techniques. As reported previously, the nickel complexes show a Col h mesophase for n =5 to 12. On the other hand, the present palladium and platinum complexes show a Col h mesophase for n =4 to 12 and n =6 to 12, respectively. Thus, they give the Col h mesophase for a shorter length of alkoxy chain in the order Pd, Ni, Pt. For 6≤ n ≤12, the clearing points become higher in the order Pt Ni>Pd. Hence, the order of stacking distances is apparently related to the order of clearing points. Moreover, the Pt, Ni and Pd complexes show reduction potentials at −0.09±0.01, −0.055±0.005, and 0.00≤0.01 V (versus SCE in CH 2 Cl 2 ), respectively. They become better π-acceptors in the order Pt