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Samenvatting
Driven by their curiosity, humans have explored uncharted parts of the Earth and beyond. Similarly, chemists investigate the chemical compound space (CCS) to search for new, undiscovered molecules for potential applications in, e.g., medicine and material sciences. Regarding our work, the quest for efficient molecular electronic devices has spiked in importance as they can potentially replace current silicon-based technologies. Thanks to their tunable chemical and photophysical properties, porphyrins and their expanded analogues have been put forward as excellent candidates for new materials, such as infrared dyes and optoelectronic devices, including nonlinear optical (NLO) switches.
One strategy to improve the photophysical properties of molecules is through traditional direct molecular design, where functionalizations, such as core-modifications and meso-substitutions, are introduced by chemical intuition. Due to the enormous size of the CCS, only small regions are traversed with this approach, hampering the discovery of novel functionalized molecules for various optical applications. By applying inverse molecular design techniques, we aim to efficiently explore larger regions of the CCS in search of promising hexaphyrin-based molecular switches as measured by their absorbance intensity and wavelength within the near-infrared region, their first-hyperpolarizability related to the Hyper-Rayleigh Scattering (βHRS), and the NLO contrast between the switch’s ON and OFF states.
In this thesis, we first link the aromaticity and structural properties of different unfunctionalized hexaphyrin conformations with distinct π-conjugation topologies and redox states to the UV/Vis absorption spectrum and βHRS. Building further on these structure-property relationships, we performed several inverse design procedures with the best-first search algorithm starting from the most favorable redox (26R → 28R and 30R → 28R) and topological switches (28M → 28R). We hereby further explored the combinatorial CCS of meso-substituted and core-modified hexaphyrins towards high-contrast NLO switches. The efficiency of the 26R → 28R and 30R → 28R is more significantly enhanced than for the 28M → 28R.
In the process, an extensive dataset was collected, and statistical analysis revealed how each type of functionalization affects the NLO responses of the [26]- and [30]hexaphyrins, and in which aspects both redox switches differ. For instance, a synergistic effect was observed between the core-modifications and meso-substituents of the optimal pattern for the 30R → 28R, while the 26R → 28R preferred to exclude core-modifications and rely solely on the synergistic effect from the push-pull meso-substitution pattern. In addition, we extended our search to multistate switches (26R → 28R → 30R), where we aimed to design switches with a similar NLO response for both ON states. By visualizing the CCS, we observed that our best-performing switches are found in regions shared by high-responsive [26]- and [30]hexaphyrins.
To further understand why these two hexaphyrin types behave so differently, machine-learning (ML) models with explainable ML techniques were designed using orbital-based, charge-transfer, and electronic features. Finally, we exploit our hexaphyrin database to generalize the structure-property relationships between aromaticity and UV/Vis-derived spectroscopic properties.
One strategy to improve the photophysical properties of molecules is through traditional direct molecular design, where functionalizations, such as core-modifications and meso-substitutions, are introduced by chemical intuition. Due to the enormous size of the CCS, only small regions are traversed with this approach, hampering the discovery of novel functionalized molecules for various optical applications. By applying inverse molecular design techniques, we aim to efficiently explore larger regions of the CCS in search of promising hexaphyrin-based molecular switches as measured by their absorbance intensity and wavelength within the near-infrared region, their first-hyperpolarizability related to the Hyper-Rayleigh Scattering (βHRS), and the NLO contrast between the switch’s ON and OFF states.
In this thesis, we first link the aromaticity and structural properties of different unfunctionalized hexaphyrin conformations with distinct π-conjugation topologies and redox states to the UV/Vis absorption spectrum and βHRS. Building further on these structure-property relationships, we performed several inverse design procedures with the best-first search algorithm starting from the most favorable redox (26R → 28R and 30R → 28R) and topological switches (28M → 28R). We hereby further explored the combinatorial CCS of meso-substituted and core-modified hexaphyrins towards high-contrast NLO switches. The efficiency of the 26R → 28R and 30R → 28R is more significantly enhanced than for the 28M → 28R.
In the process, an extensive dataset was collected, and statistical analysis revealed how each type of functionalization affects the NLO responses of the [26]- and [30]hexaphyrins, and in which aspects both redox switches differ. For instance, a synergistic effect was observed between the core-modifications and meso-substituents of the optimal pattern for the 30R → 28R, while the 26R → 28R preferred to exclude core-modifications and rely solely on the synergistic effect from the push-pull meso-substitution pattern. In addition, we extended our search to multistate switches (26R → 28R → 30R), where we aimed to design switches with a similar NLO response for both ON states. By visualizing the CCS, we observed that our best-performing switches are found in regions shared by high-responsive [26]- and [30]hexaphyrins.
To further understand why these two hexaphyrin types behave so differently, machine-learning (ML) models with explainable ML techniques were designed using orbital-based, charge-transfer, and electronic features. Finally, we exploit our hexaphyrin database to generalize the structure-property relationships between aromaticity and UV/Vis-derived spectroscopic properties.
Originele taal-2 | English |
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Toekennende instantie |
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Begeleider(s)/adviseur |
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Datum van toekenning | 10 dec. 2024 |
Uitgever | |
Gedrukte ISBN's | 9789464948776 |
Status | Published - 2024 |
Projecten
- 1 Afgelopen
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FWOTM1013: Rationeel moleculair ontwerp van fotoschakelaars voor niet-lineaire optische toepassingen
Desmedt, E., Alonso Giner, M. & De Vleeschouwer, F.
1/11/20 → 31/10/24
Project: Fundamenteel