Tetra (4-propargyloxyphenoxy)phthalocyanines: Facile synthesis, fluorescence and thermal properties

Abstract

The facile method of synthesizing of tetra (4-propargyloxyphenoxy) phthalocyanines with the terminal alkynyl (CC) group is reported. The synthesized phthalocyanines are the unmetallated (H2TPrOPhOPc) and the metallated complexes of cobalt (CoTPrOPhOPc) and manganese (Mn(OAc)TPrOPhOPc). The fluorescence properties of H2TPrOPhOPc and Mn(OAc)TPrOPhOPc were investigated. The fluorescence lifetimes (τF) for the H2TPrOPhOPc and Mn(OAc)TPrOPhOPc, evaluated using time correlated single photon counting (TCSPC) technique, were found to be 5.79ns and 5.50ns, respectively. The fluorescence quantum yields (ΦF) were also calculated using a comparative method and were 0.12 for H2TPrOPhOPc and 0.16 for Mn(OAc)TPrOPhOPc. The CoTPrOPhOPc complex did not show fluorescent properties and this was attributed to the quenching of the excited state by the half-filled metal d-orbitals which are lying below the highest occupied molecular orbitals (HOMO) of the phthalocyanine ring. The CoTPrOPhOPc and Mn(OAc)TPrOPhOPc exhibited excellent thermal stability, which was better than H2TPrOPhOPc, due to the presence of the cobalt and manganese metal ions at the centre of the phthalocyanine ring. Density functional theory (DFT) calculations predicted the HOMO−LUMO (lowest unoccupied molecular orbitals) gap for H2TPrOPhOPc, CoTPrOPhOPc and Mn(OAc)TPrOPhOPc to be 2.06eV, 2.15eV and 1.75eV, respectively.