Insights into the New Cadmium(II) Metalloporphyrin: Synthesis, X-ray Crystal Structure, Hirshfeld surface analysis, Photophysical and Cyclic voltammetry Characterization of the (Morpholine){(meso-tetra(para-chloro-phenyl)porphyrinato}cadmium(II)

Abstract In this work we report the synthesis of the cadmium(II)- meso -tetra( para -chloro-phenyl)porphyrin with the morpholine O -donor axial ligand with formula [Cd(TClPP)(morph)] ( I ). This coordination compound adopts a distorted five-coordinate square pyramidal geometry indicated by a major doming , a moderate ruffling and saddle distortions of the porphyrinato core. The supramolecular architecture is dominated by intermolecular N−H···Cl and C−H···Cl interactions formed between the morpholine and the chlorine atom of the adjacent meso- phenylporphyrin of complex ( I ). Hirshfeld surface analysis was carried out to understand the nature of intermolecular contacts, where the fingerprint plot provides the information about the percentage contribution. UV-visible spectroscopy study highlighted the red-shift of the absorption bands after the insertion of Cd(II) metal ion into TClPP moiety and after coordination of the morpholine axial ligand. Fluorescence emission spectroscopy study showed a remarkable blue-shift effect of the Q bands followed by a dramatical diminution of the fluorescence intensity, quantum yield (φ f ) and lifetime (τ f ) as consequence of the high quenching effect of the cadmium heavy metal and the distortion of the porphyrin core, which promotes the loss of the “motion energy” by other non-radiative energy dissipation processes than light emission. An increase of the singlet oxygen quantum yield (Φ Δ ) is also observed due to the heavy atom effect of cadmium(II) cation. The cyclic voltammetry investigation of the free base H 2 TClPP, the starting material [Cd(TClPP)] and the Cd(II)-morpholine porphyrin species (I) is also reported.