The 16th Femtochemistry Conference (FEMTO16)

Deciphering the ultrafast photobehavior of benzothiadiazole-based HOFs and its molecular units: experimental and theoretical insights into their spectroscopic properties in solution and in the solid state

Jun 27, 2025, 9:30 AM

20m

Contributed talk Session 15 - Materials II

Speaker

Abderrazzak Douhal (Universidad de Castilla la Mancha)

Description

Benzothiadiazole (BTD) derivatives have emerged as versatile building blocks for the fabrication of smart porous materials. Herein, we report on experimental and theoretical studies of two BTD-based H-bonded organic frameworks (HOFs) and their molecular units (MUs) in solutions and in solid state (BTIA and BTTA).1-3 The MUs in solutions exhibit a photoinduced intramolecular charge-transfer (ICT) reaction in the excited species followed by a twisting motion of phenyl moieties. Femtosecond (fs) experiments reveal that the ICT event takes place in ∼300 fs while the phenyl torsion occurs in ∼6 ps and ~10 ps for BTIA and BTTA, respectively. Ester-derivatives show a single emission lifetime of ~7 ns, while the acidvderivatives display lifetimes of ~ 400 ps and ~1 and ~7 ns assigned to different emitting species. Theoretical calculations on the ester compounds agree with the experimental observations. In solid state, the ester derivatives show an abnormally slow ICT event (80 ps) leading to ICT aggregates with lifetimes of ~1 and ~3 ns, whereas single crystal of BTD-HOFs under the microscope exhibit a fast ICT and intermolecular proton-transfer (PT) reactions (<15 ps), producing ICT and ionic species with lifetimes of ~500 ps and ~1 ns, respectively. These results provide new findings for a better understanding of the photobehavior of BTD related HOF materials and will help in the development of new HOFs for photonic applications.
Acknowledgement: This research was supported by PID2020-116519RB-I00 funded by MICIU/AEI/10.13039/501100011033 and by the “European Union, EU”; SBPLY/23/180225/000196 funded by JCCM and the EU through “Fondo Europeo de Desarollo Regional” (FEDER), and 2022-GRIN-34325 funded by UCLM (FEDER). MH thanks MCIN for the FPI fellowship PRE2021-099064 financed by MCIN/AEI/10.13059/501100011033.
References:
[1] Z. Yang, A. Moriyama, R. Oketani, T. Nakamura, I. Hisaki. Chem. Lett. 2021, 50, 1909-1912.
[2] Z. Yang, A. Saeki, A. Inoue, R. Oketani, K. Kamiya, S. Nakanishi, T. Nakamura, I. Hisaki. Cryst. Growth Des. 2022, 22, 4472−4479.
[3] M. de la Hoz Tomás, J. A. Organero, M. R. di Nunzio, T. Hashimoto, I. Hisaki, A. Douhal. J. Mater. Chem. C, 2024, 12, 9112-9129.