Synthesis of new chlorin e6 trimethyl and protoporphyrin IX dimethyl ester derivatives and their photophysical and electrochemical characterizations

José C J M D S Menezes, M. Amparo F Faustino, Kleber T. De Oliveira, Marciana P. Uliana, Vitor F. Ferreira, Steffen Hackbarth, Beate Röder, Thiago Teixeira Tasso, Taniyuki Furuyama, Nagao Kobayashi, Artur M S Silva, M. Graça P M S Neves, José A S Cavaleiro

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2 Citations (Scopus)


In view of increasing demands for efficient photosensitizers for photodynamic therapy (PDT), we herein report the synthesis and photophysical characterizations of new chlorin e6 trimethyl ester and protoporphyrin IX dimethyl ester dyads as free bases and ZnII complexes. The synthesis of these molecules linked at the β-pyrrolic positions to pyrano[3,2-c]coumarin, pyrano[3,2-c]quinolinone, and pyrano[3,2-c]naphthoquinone moieties was performed by using the domino Knoevenagel hetero Diels-Alder reaction. The α-methylenechromanes, α-methylenequinoline, and ortho-quinone methides were generated in situ from a Knoevenagel reaction of 4-hydroxycoumarin, 4-hydroxy-6-methylcoumarin, 4-hydroxy-N-methylquinolinone, and 2-hydroxy-1,4-naphthoquinone, respectively, with paraformaldehyde in dioxane. All the dyads as free bases and as ZnII complexes were obtained in high yields. All new compounds were fully characterized by 1D and 2D NMR techniques, UV/Vis spectroscopy, and HRMS. Their photophysical properties were evaluated by measuring the fluorescence quantum yield, the singlet oxygen quantum yield by luminescence detection, and also the triplet lifetimes were correlated by flash photolysis and intersystem crossing (ISC) rates. The fluorescence lifetimes were measured by a time-correlated single photon count (TCSPC) method, fluorescence decay associated spectra (FDAS), and anisotropy measurements. Magnetic circular dichroism (MCD) and circular dichroism (CD) spectra were recorded for one ZnII complex in order to obtain information, respectively, on the electronic and conformational states, and interpretation of these spectra was enhanced by molecular orbital (MO) calculations. Electrochemical studies of the ZnII complexes were also carried out to gain insights into their behavior for such applications.

Original languageEnglish
Pages (from-to)13644-13655
Number of pages12
JournalChemistry - A European Journal
Issue number42
Publication statusPublished - 2014 Oct 1


  • Chlorin e
  • hetero Diels-Alder
  • Knoevenagel
  • photophysics
  • porphyrinoids

ASJC Scopus subject areas

  • Chemistry(all)


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