Holmium porphyrin compound liquid crystals: Synthesis and properties

5,10,15,20-Tetra-(p-alkoxy-m-ethyloxy)phenyl]porphyrin and 5-(p-alkoxy)phenyl-10,15,20-tri-phenyl]porphyrin and their holmium(III) complexes are reported. They display a hexagonal columnar discotic columnar (Col_h) liquid crystal phase and were studied by cyclic voltammetry, surface photovoltage spectroscopy (SPS), electric-field-induced surface photovoltage spectroscopy (EFISPS) and luminescence spectroscopy. Within the accessible potential window, all these compounds exhibit two one-electron reversible redox reactions. Quantum yields of Q band are in the region 0.0045–0.21 at room temperature. The SPS and EFISPS reveal that all the compounds are p-type semiconductors and exhibit photovoltaic response due to π–π^* electron transitions.