An unsymmetrical porphyrin and its metal complexes: Synthesis, spectroscopy, thermal analysis and liquid crystal properties

Abstract

The synthesis and characterization of a new unsymmetrical porphyrin liquid crystal, 5-(4-stearoyloxyphenyl)phenyl-10,15,20-triphenylporphyrin (SPTPPH2) and its transition metal complexes (SPTPPM, M(II) = Zn, Fe, Co, Ni, Cu or Mn) are reported. Their structure and properties were studied by elemental analysis, and UV-Vis, IR, mass and 1H-HMR spectroscopy. Their luminescent properties were studied by excitation and emission spectroscopy. The quantum yields of the S1 → S0 fluorescence were measured at room temperature. According to thermal studies, the complexes have a higher thermal stability (no decomposition until 200°C). Differential scanning calorimetry (DSC) data and an optical textural photograph, obtained using a polarizing microscope (POM), indicate that the porphyrin ligand had liquid crystalline character and that it exhibited more than one mesophase and a low-lying phase transition temperature, with transition temperatures of 19.3 and 79.4°C; the temperature range of the liquid crystal (LC) phase of the ligand was 70.1°C.

Keywords

• porphyrin
• transition metal complex
• fluorescence spectroscopy
• liquid crystal