Ethyl acetoacetate and acetylacetone appended hexabromo porphyrins: synthesis, spectral, electrochemical, and femtosecond third-order nonlinear optical studies.

Asymmetrically substituted porphyrins possessing ethyl acetoacetate or acetylacetone (EAA or acac) with six bromine atoms at β-positions were synthesized and then characterized by various spectroscopic techniques, such as UV-Vis, fluorescence and NMR, and also by CV, DFT, MALDI-TOF-MS and elemental analysis. The mechanistic pathway followed the nucleophilic substitution reaction (nucleophile: EAA and acac) with MTPP(NO)Br (M = 2H, Cu(II), and Ni(II)), and the resultant β-heptasubstituted porphyrins exhibited keto-enol tautomerism, as supported by H NMR spectroscopy. The six bulky bromo and EAA/acac groups made the macrocyclic ring highly electron deficient and nonplanar such that the quantum yield and fluorescence intensity for HTPP[EAA]Br and HTPP[acac]Br were severely reduced in contrast to those values for HTPP.