Synthesis, photoinduced amination and topological indices of novel porphyrin dyads

Transition-metal-catalyzed homo and hetero coupling is a rapidly growing area of research. This work refers to the nickel-catalyzed photoinduced amination study of β-bromotetraarylporphyrin and its Ni(II), Zn(II) and Cu(II) complexes. The selective mono β-bromination of 5,10,15,20-tetrakis(4′-isopropylphenyl)porphyrin was achieved with N-bromosuccinimide. Under similar conditions, β-bromination of Ni(II), Zn(II) and Cu(II) complexes of 5,10,15,20-tetrakis(4′-isopropylphenyl)porphyrin successfully afforded the corresponding 2-bromometalloporphyrins. The β-bromoporphyrin/metalloporphyrins were coupled with three different amines through the creation of the C-N bond by using an economical and air-tolerant photoactive catalyst (NiBr2 · 3H2O) at room temperature under 365 nm radiations. Nickel-catalyzed amination yields are compared with the traditional Buchwald-Hartwig amination yields. Due to the low operational cost, photoinduced nickel-catalyzed C-N couplings were found to be more economical than the Buchwald-Hartwig amination procedure, although the latter afforded higher yields. The nickel-catalyzed photoamination reaction was also extended for the one-pot synthesis of pyridine-3,5-diamine bridged porphyrin dyad. The intramolecular cyclization of the pyridine-3,5-diamine-bridged porphyrin dyad afforded a novel quinolino-fused porphyrin dyad. Degree-and distance-based topological indices of the newly synthesized porphyrins were calculated and correlated with their molar refractivity. All newly synthesized porphyrins are characterized by UV-vis, FTIR, 1H NMR, elemental analysis and mass spectrometry.