New trans-AB2C meso-substituted porphyrin amino acid esters with meso-substituents of tunable electron withdrawing power (B = mesityl, 4-C 6H4F, 4-C6H4CF3, C 6F5) were prepared as free amines 3a-3d, as N-acetylated derivatives Ac-3a-Ac-3d and corresponding zinc(ii) complexes Zn-Ac-3a-Zn-Ac-3d. Several amide-linked bis(porphyrins) with a tunable electron density at each porphyrin site were obtained from the amino porphyrin precursors by condensation reactions (4a-4d) and mono- and bis(zinc(ii)) complexes Zn2-4d and Zn1Zn2-4d were prepared. The electronic interaction between individual porphyrin units in bis(porphyrins) 4 is probed by electrochemical experiments (CV, EPR), electronic absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy in combination with DFT/PCM calculations on diamagnetic neutral bis(porphyrins) 4 and on respective charged mixed-valent radicals 4+/-. The interaction via the -C 6H4-NHCO-C6H4- bridge, the site of oxidation and reduction and the lowest excited singlet state S1, is tuned by the substituents on the individual porphyrins and the metalation state.
ASJC Scopus subject areas
- Inorganic Chemistry