Synthesis and Optical Features of Axially and Peripherally Substituted Subporphyrins. A Paradigmatic Example of Charge Transfer versus Exciplex States
Winterfeld K, Lavarda G, Yoshida K, Bayerlein MJ, Kise K, Tanaka T, Osuka A, Guldi DM, Torres T, Bottari G (2020)
Publication Type: Journal article
Publication year: 2020
Journal
Book Volume: 142
Pages Range: 7920-7929
Journal Issue: 17
DOI: 10.1021/jacs.0c01646
Abstract
We report here the synthesis of two novel subporphyrins (SubPs), in which the macrocycle has been functionalized at its meso (1) or axial (2) position with tetracyanobuta-1,3-diene (TCBD)-aniline. In-depth spectroscopic, spectrometric, and electrochemical analyses were carried out with both of them, whose molecular structures were determined by single-crystal X-ray diffraction studies. In the case of 2, its Ra and Sa enantiomers were separable by chiral HPLC and presented a fairly good configurational stability at room temperature, which enabled determining the activation parameters for the thermally induced racemization. Conversely, the enantiomers' separation was unfeasible for 1 due to the conformational and/or configurational dynamics of the TCBD-aniline, a structural "flexibility" that could be drastically reduced at low temperatures. The physicochemical impact of placing the TCBD-aniline at either the axial or peripheral positions of SubPs is also rather significant. The HOMO-LUMO gap is reduced by as much as 0.35 eV in SubP-(TCBD-aniline)meso 1 (1.77 eV) and, in turn, enables an emissive charge-transfer (CT) state in virtually all environments. It is only in polar environments, where it links a local excitation with an indirect charge separation. In contrast, a much larger HOMO-LUMO gap of 2.12 eV in SubP-(TCBD-aniline)axial 2 disables an emissive CT state and enforces either an exciplex deactivation in apolar environments or a direct charge separation in polar environments.
Authors with CRIS profile
Kim Winterfeld
Lehrstuhl für Physikalische Chemie I
Dirk Michael Guldi
Lehrstuhl für Physikalische Chemie I
Involved external institutions
Japan (JP)
Spain (ES)How to cite
APA:
Winterfeld, K., Lavarda, G., Yoshida, K., Bayerlein, M.J., Kise, K., Tanaka, T.,... Bottari, G. (2020). Synthesis and Optical Features of Axially and Peripherally Substituted Subporphyrins. A Paradigmatic Example of Charge Transfer versus Exciplex States. Journal of the American Chemical Society, 142(17), 7920-7929. https://dx.doi.org/10.1021/jacs.0c01646
MLA:
Winterfeld, Kim, et al. "Synthesis and Optical Features of Axially and Peripherally Substituted Subporphyrins. A Paradigmatic Example of Charge Transfer versus Exciplex States." Journal of the American Chemical Society 142.17 (2020): 7920-7929.
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