meso-Indolo[3,2-b]carbazolyl-Substituted Porphyrinoids: Synthesis, Characterization and Effect of the Number of Indolocarbazole Moieties on the Photophysical Properties

• Published in: European Journal of Organic Chemistry Vol. 2010; no. 13; pp. 2576 - 2586
• Main Authors: Maes, Wouter, Ngo, Thien H., Rong, Gu, Starukhin, Aleksander S., Kruk, Mikalai M., Dehaen, Wim
• Format: Book Review Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01-05-2010; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Chemistry; Exact sciences and technology; Excitation energy deactivation; General and physical chemistry; Heterocyclic compounds; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Luminescence; Molecular electronics; Nitrogen heterocycles; Organic chemistry; Photochemistry; Photophysical properties; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Porphyrinoids; Preparations and properties; Nitrogen heterocycle; Zinc complex; Luminescence; Fluorescence; Luminescent material; Photochemical reaction; Macrocycle; Characterization; Oxygen molecules; Optical properties; Metalloporphyrin; Excitation energy; Chemical synthesis; Condensation reaction; Deactivation; Singlet state; Transition metal Complexes; Quantum yield; Porphyrinoids; Molecular electronics; Fluorescence yield; Nitrogen heterocycles; Excitation energy deactivation; Bathochromism; Photophysical properties; Porphyrin derivatives
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201000180

meso‐Indolocarbazolylporphyrins endowed with a different number of indolocarbazole units have been synthesized via condensation of an appropriately substituted monoformylated 5,11‐dihydroindolo[3,2‐b]carbazole precursor and mesityldipyrromethane. Under specific conditions, analogous meso‐indolocarbazolylcorroles could also be prepared. The photophysical features of the novel luminescent free‐base and Zn‐porphyrin derivatives were investigated. The introduction of indolocarbazole substituents results in progressive bathochromic shifts of the porphyrin absorbance and fluorescence bands due to the rising energy of the a2u orbital. The excitation energy is efficiently transferred from the meso‐indolocarbazole units to the porphyrin macrocycle. An increased number of indolocarbazole moieties does not lead to porphyrin fluorescence quenching; on the contrary, a small increase of the fluorescence quantum yield is observed. The main route for excitation energy deactivation of all the studied porphyrins is intersystem S1→T1 crossing, with the intersystem crossing quantum yield, as determined by the photosensitized formation of singlet molecular oxygen, being as high as about 70 % for the free‐bases and more than 80 % for the Zn complexes. The intersystem crossing quantum yield seems to be barely affected by meso‐indolocarbazole substitution. A noticeable part of the excitation energy was found to deactivate through radiationless internal S1→S0 conversion.
The synthesis and photophysical study ofmeso‐indolo[3,2‐b]carbazolyl‐substitutedporphyrinoids are reported. The combination of a luminescent porphyrin or corrole core moiety with appended energy and charge‐transporting indolocarbazole substituents affords interesting photophysical probes and provides novel prospects in the area of semiconducting organic materials.