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Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives.

ABSTRACT: We synthesized new pyrene derivatives with strong bis(para-methoxyphenyl)amine donors at the 2,7-positions and n-azaacene acceptors at the K-region of pyrene. The compounds possess a strong intramolecular charge transfer, leading to unusual properties such as emission in the red to NIR region (700?nm), which has not been reported before for monomeric pyrenes. Detailed photophysical studies reveal very long intrinsic lifetimes of >100?ns for the new compounds, which is typical for 2,7-substituted pyrenes but not for K-region substituted pyrenes. The incorporation of strong donors and acceptors leads to very low reduction and oxidation potentials, and spectroelectrochemical studies show that the compounds are on the borderline between localized Robin-Day class-II and delocalized Robin-Day class-III species.

SUBMITTER: Merz J

PROVIDER: S-EPMC6973242 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives.

Merz Julia J Dietz Maximilian M Vonhausen Yvonne Y Wöber Frederik F Friedrich Alexandra A Sieh Daniel D Krummenacher Ivo I Braunschweig Holger H Moos Michael M Holzapfel Marco M Lambert Christoph C Marder Todd B TB

Chemistry (Weinheim an der Bergstrasse, Germany) 20191119 2

We synthesized new pyrene derivatives with strong bis(para-methoxyphenyl)amine donors at the 2,7-positions and n-azaacene acceptors at the K-region of pyrene. The compounds possess a strong intramolecular charge transfer, leading to unusual properties such as emission in the red to NIR region (700 nm), which has not been reported before for monomeric pyrenes. Detailed photophysical studies reveal very long intrinsic lifetimes of >100 ns for the new compounds, which is typical for 2,7-substituted ...[more]

PMID: 31593316

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Project description:In order to develop new organic materials for optoelectronic applications, a fundamental understanding of the electronic properties of specific chromophore combinations must be realized. To that end, we report "model" acceptor (A)-acceptor' (A')-acceptor (A) triads in which the pendants (A') we selected are well-known components of organic optoelectronic applications. Our pendants are sandwiched between two dialkoxyphenazine (A) through an alkyne bond. The A' was systematically increased in electron-deficiency from benzothiadiazole (BTD-P) to naphthalene diimide with octyl (NDI-O-P) or ethylhexyl groups (NDI-EH-P) to perylene diimide with ethylhexyl (PTCDI-EH-P) to assess changes in the electronic properties of the resultant molecules. Characterizations were performed using both experimental and theoretical methods. From optical and cyclic voltammetry, we found that the electron deficiency of each pendant was directly correlated to the energy level of the lowest unoccupied molecular orbital (E LUMO). When examining the simple molecular orbital diagrams produced at the B3LYP/6-31G* level of theory, the LUMOs were, as expected, primarily localized on the more electron-deficient pendants. In terms of the energy level of the highest occupied molecular orbital (E HOMO), the numerical values obtained experimentally also correlated with values obtained computationally. Attempting to construct a simplified model that would explain these correlated values was not as readily apparent, given the disparate physical characteristics of these compounds. For example, BTD-P and NDI-O-P/NDI-EH-P achieved planarity when computationally optimized, but PTCDI-EH-P adapted a "buckled" geometry on the central PTCDI, consequently forcing the attached phenazines out-of-plane. The title compounds showed solvent polarity-dependent fluorescence, which is indicative of intramolecular charge transfer. In conjunction with our theoretical study, the current system can be viewed as an extension of donor-acceptor-donor systems. Thermal properties characterized by differential scanning calorimetry revealed that reversible phase transitions were only observed for BTD-P. In addition, BTD-P was found to be an efficient gelator in 1,1,1-trichloroethane and toluene. The other compounds in this study did not form gels in any of the solvents tested, which may have been a result of the alkyl groups on the pendants hampering the fibrillation process.

Dataset Information

Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives.

Publications

Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives.

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