Discotic liquid crystals of transition metal complexes, 55: Novel chlorine-substituted phthalocyanine derivatives showing mesomorphism and low HOMO energy level

Abstract

We have synthesized a series of novel phthalocyaninato copper(II) (abbreviated as PcCu) compounds, 1,4,8,11,15,18,22,25-octakisalkoxy-2,3,9,10,16,17,23,24-octachloro-phthalocyaninato copper(II) (abbreviated as ([Formula: see text]-C[Formula: see text]O)[Formula: see text]-Cl)[Formula: see text]PcCu (4a–4d): [Formula: see text] 6 (a), 8 (b), 10 (c) and 12 (d)) and, for comparison, another series of PcCu compounds, 1,4,8,11,15,18,22,25-octakisalkoxyphthalocyaninato copper(II) (abbreviated as ([Formula: see text]-C[Formula: see text]O)[Formula: see text]PcCu (1a–1d)). The PcCu derivatives 1a–1d are substituted by alkoxy chains only at the [Formula: see text] positions (1,4,8,11,15,18,22,25). On the other hand, the PcCu derivatives 4a–4d are substituted by alkoxy chains at the [Formula: see text] positions and chlorine atoms at the [Formula: see text] positions (2,3,9,10,16,17,23,24). We have investigated the influence of chlorine atoms substituted at the [Formula: see text] positions of the Pc ring on mesomorphism, spectroscopic and electronic properties for these two series of PcCu derivatives 1 and 4 by using a polarizing optical microscope, DSC, temperature-variable small angle X-ray diffractometer, a UV-Vis spectrophotometer and cyclic voltammetry. Each of the derivatives 1a–1d is crystalline without showing mesomorphism. On the other hand, each of the chlorine-substituted PcCu derivatives 4a–4d shows plural phase transitions, and the longer chain-substituted PcCu derivatives 4c–4d show a rectangular ordered columnar [Col[Formula: see text](P2m)] mesophase. Furthermore, we have revealed that each of the PcCu derivatives 4a–4d shows a Q-band in the near-infrared region and a lower HOMO energy level than conventional phthalocyanine derivatives.