Discotic liquid crystals of transition metal complexes, 53†: synthesis and mesomorphism of phthalocyanines substituted by m-alkoxyphenylthio groups

Abstract

We have successfully synthesized a series of novel octakis([Formula: see text]-alkoxyphenylthio)phthalocyaninato copper(II) complexes, ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PcCu ([Formula: see text] = 2, 4, 6, 8, 10, 12, 14, 16: 1b~1i), by our developed method to reveal their mesomorphism. The phase transition behavior and mesophase structures have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. Interestingly, the very short chain-substituted derivatives, ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PcCu (1a) and ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PCu (1b), show a hexagonal ordered columnar (Col[Formula: see text] mesophase, whereas each of the other longer-chain-substituted derivatives, ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PcCu ([Formula: see text] = 4~16: 1c~1i), shows only rectangular ordered columnar (Col[Formula: see text] mesophase(s). In contrast to the present longer-chain-substituted phenylthio derivatives, each of the previous longer-chain-substituted phenoxy derivatives, ([Formula: see text]-C[Formula: see text]OPhO)[Formula: see text]PcCu ([Formula: see text] = 10–20), shows a different columnar mesophase of Col[Formula: see text]. We discuss this difference of mesomorphism from the viewpoint of the different steric hindrance originated by the peripheral substituents, PhO and PhS groups. Moreover, we could estimate the optical band gaps of ([Formula: see text]-C[Formula: see text]OPhO)[Formula: see text]PcCu and ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PcCu (1f) from absorption edge of the Q-bands to be 1.79 eV and 1.70 eV, respectively. Therefore, the phenylthio-substituted derivative gave a narrower band gap byca. 0.1 eV in comparison with the phenoxy-substituted derivative.