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ISSN 1998-9539

Spectral-Luminescent Properties of meso-Tetraarylporphyrins Revisited: The Role of Aryl Type, Substitution Pattern and Macrocycle Core Protonation

Irina V. Vershilovskaya,a Stefano Stefani,b Pieter Verstappen,c Thien H. Ngo,b,d@1 Ivan G. Scheblykin,e Wim Dehaen,f Wouter Maes,c@2 and Mikalai M. Kruka@3
aBelarussian State Technological University, Physics Department, 220006 Minsk, Belarus
bInstitut für Chemie und Biochemie, Freie Universität Berlin, 14195 Berlin, Germany
cDesign & Synthesis of Organic Semiconductors (DSOS), Institute for Materials Research (IMO-IMOMEC), Hasselt University, B-3590 Diepenbeek, Belgium
dInternational Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 305-0044 Tsukuba, Ibaraki, Japan
eLund University, Division of Chemical Physics, 22100 Lund, Sweden
fMolecular Design and Synthesis, Department of Chemistry, KU Leuven, B-3001 Leuven, Belgium
@1Corresponding author E-mail:;
@2Corresponding author E-mail:
@3Corresponding author E-mail:
DOI: 10.6060/mhc160962n
Macroheterocycles 2017 10(3) 257-267
Both the ground (S0) and the lowest singlet excited states (S1) for a series of 5,10,15,20-tetraarylporphyrins consisting of two symmetrically and four asymmetrically substituted derivatives (A4, AB3, trans-A2B2, cis-A2B2, A3B and B4, where A=phenyl and B=mesityl) are studied by absorption and fluorescence spectroscopies. The rotational degree of freedom of the aryl rings is found to play a crucial role in the discrimination between the radiative and radiationless decays of the S1 states. This feature is dramatically enhanced upon going from the free base molecules to their mono- and diprotonated forms because of the nonplanar macrocycle conformation of the latters. The progressive A to B replacement of the aryl substituents leads to additive spectral changes over the whole series in the free base form. For both mono- and diprotonated species such a gradual additive pattern is broken by a “spectral jump” from the trans to the cis derivative, which is proposed to be a signature of the transition between two macrocycle conformations with different flexibility.


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