Synthesis, structural, spectral and electrochemical studies of β-acetamide appended porphyrins

Mono [Formula: see text]-acetamide appended porphyrins, MTPP(NHCOMe) (M = 2H, Zn II , Cu II , Ni II , Co II , Mn III and V IV , TPP = meso-tetraphenylporphyrin) were synthesized and characterized by various spectroscopic techniques. The effect of the [Formula: see text]-substituents and core metal ions on the electronic spectra was evaluated. The free base and Zn II porphyrins exhibited weak emission and a lower singlet state lifetime than H 2 TPP and ZnTPP. The first ring reduction potential of MTPP(NHCOMe) (M = Co II , Ni II , Cu II , Zn II , V IV porphyrins exhibited a 10-70 mV cathodic shift whereas, free base and Mn III derivatives showed 10-100 mV anodic shift than corresponding MTPPs. The slightly saddled-shaped structures of CuTPP(NHCOMe), ZnTPP(NHCOMe), and Mn(Cl)TPP(NHCOMe) were confirmed by the single crystal X-ray diffraction analysis. Density functional theory (DFT) studies revealed that the NiTPP(NHCOMe) has the highest average deviation of the 24-core atom from the mean porphyrin plane, [Formula: see text]24 (± 0.278 Å) and the average displacement of [Formula: see text]-pyrrole carbons from the porphyrin mean plane, [Formula: see text]C[Formula: see text] (± 0.278 Å) values among all the synthesized porphyrins. The HOMO-LUMO gap observed from DFT and Cyclic voltammetry studies are qualitatively comparable. The EPR spectroscopy confirmed the +4 oxidation state of the vanadyl ion, exhibited by the comparable eight-line pattern.