Subphthalocyanine-spiropyran - a versatile system to study photoswitchable fluorescence
Final Report Abstract
In the context of this project, the current state of research in the field of subphthalocyanines (SubPc’s) was collected in a review article. This article focused on the influence of different structures and substituents on the photophysical properties of SubPc’s. However, the syntheses that were proposed originally did not lead to success. Nevertheless, a new combination of two photoswitching molecules was synthesized. The dyad of dihydroazulene (DHA) and spiropyran (SP) could occupy eight different states. Two of those states are thermally stable and can be interconverted by protonation/deprotonation. From these two states, six other states can be reached by either irradiation or addition of an acid or base. The metastable states show half-life times that range from less than 30 seconds to multiple hours. Most interestingly, the connection of DHA and SP gave rise to remarkable fluorescence behavior. The quantum yield of the emission is two orders of magnitude larger than previously reported fluorescence of DHA. Moreover, the emission wavelength and thus the color of the fluorescence strongly depend on the polarity of the solvent. Solvents of low polarity such as cyclohexane gave blue fluorescence, medium polarity solvents such as dichloromethane gave yellow and highly polar solvents such as acetonitrile gave red fluorescence. Because of this polarity dependence, we assume a new emission mechanism for this class of compounds. The found emitting system is currently being investigated in several synthetic projects and a new collaboration was established to explain the emission properties by theoretical models.
Publications
- “Controlling the optical properties of boron subphthalocyanines and their analogues”, Mol. Syst. Des. Eng. 6, 6-24.
M. Dowds, M. B. Nielsen
(See online at https://doi.org/10.1039/d0me00150c) - “Five-State photo- and acidochromism“, The International Chemical Congress of Pacific Basin Societies 12/2021, online.
- “More than the sum of its parts: A modular dihydroazulene-spiropyran photo switchable dyad”, KOPO 2022 – Conjugated Oligomers and Polymers 10/2022, Bad Honnef, Germany.
- “More than the sum of its parts: A modular dihydroazulene-spiropyran photo switchable dyad”, Mach-5: Molecular Machinery, Making, Measuring, Modeling 09/2022, Plön, Germany
- “Orthogonal- and Path-Dependent Photo/Acidoswitching in an Eight-State Dihydroazulene-Spiropyran Dyad”, ChemPhotoChem 6, e202200152.
M. Dowds, S. G. Stenspil, J. H. de Souza, B. W. Laursen, M. Cacciarini, M. B. Nielsen
(See online at https://doi.org/10.1002/cptc.202200152) - “Photo- and acidochromism in dihydrazulene-spiropyran systems”, Universität Bremen, Bremen, Germany.
