A Molecular Photosensitizer in a Porous Block Copolymer Matrix‐Implications for the Design of Photocatalytically Active Membranes

Abstract

Recently, porous photocatalytically active block copolymer membranes were introduced, based on heterogenized molecular catalysts. Here, we report the integration of the photosensitizer, i. e., the light absorbing unit in an intermolecular photocatalytic system into block copolymer membranes in a covalent manner. We study the resulting structure and evaluate the orientational mobility of the photosensitizer as integral part of the photocatalytic system in such membranes. To this end we utilize transient absorption anisotropy, highlighting the temporal reorienta-tion of the transition dipole moment probed in a femtosecond pump-probe experiment. Our findings indicate that the photosensitizer is rigidly bound to the polymer membrane and shows a large heterogeneity of absolute anisotropy values as a function of location probed within the matrix. This reflects the sample inhomogeneity arising from different protonation states of the photosensitizer and different intermolecular interactions of the photosensitizers within the block copolymer membrane scaffold.

Triplet Formation and Triplet‐Triplet Annihilation Upconversion in Iodine Substituted Non‐Orthogonal BODIPY‐Perylene Dyads

“…Femtosecond time-resolved absorption (fs-TA) measurements were performed using a home-built setup reported earlier. [33,34] Samples were placed in 1 mm pathlength quartz-made inert cuvettes for all fs-TA measurements and absorbance for all the samples at excitation wavelength is ~0.35. The pump pulse power was ~20 μJ.…”

A BODIPY‐Based Molecular Rotor in Giant Unilamellar Vesicles: A Case Study by Polarization‐Resolved Time‐Resolved Emission and Transient Absorption Spectroscopy

“…In such cases, time‐resolved transient absorption anisotropy (TAA) might complement time‐resolved fluorescence anisotropy measurements to investigate molecular motion, e. g., in cells, cell membranes or cell membrane models. TAA probes the rotational diffusion of both emissive and non‐emissive molecules by using two orthogonally polarized probe beams (see Figure 1 for a schematic depiction) [25–27] . For instance, nanosecond transient absorption anisotropy has been used to evaluate rotational diffusion coefficients of bacteriorhodopsin (BR) in dimyristoylphosphatidylcholine (DMPC) and egg phosphatidylcholine [28] .…”

“…TAA probes the rotational diffusion of both emissive and non-emissive molecules by using two orthogonally polarized probe beams (see Figure 1 for a schematic depiction). [25][26][27] For instance, nanosecond transient absorption anisotropy has been used to evaluate rotational diffusion coefficients of bacteriorhodopsin (BR) in dimyristoylphosphatidylcholine (DMPC) and egg phosphatidylcholine. [28] Here, we present -to the best of our knowledge -the first femtosecond transient absorption anisotropy of BODIPY-derivatives in GUVs to investigate the local mobility of the chromophoric part of the molecules (see Figure 1) bound to the model membrane by an extended molecular linker and relate this data to TEA results on the same fluorophore.…”

Growing Spicy ONIOMs: Extending and generalizing concepts of ONIOM and many body expansions

“…We are interested in describing interactions in electronically active soft matter materials, often in conjunction with embedded (photo)catalysts. For example, the integration of (photo)catalysts or photosensitizers into tailored polymer membranes can synergistically improve the stability of the active species and kinetic aspects while simplifying the handling of compounds sensitive to oxygen exposure 55,56 . An accurate description of their electronic properties and rich photochemistry prohibits their sole treatment by molecular mechanics (MM) methods.…”

“…For example, the integration of (photo)catalysts or photosensitizers into tailored polymer membranes can synergistically improve the stability of the active species and kinetic aspects while simplifying the handling of compounds sensitive to oxygen exposure. 55,56 An accurate description of their electronic properties and rich photochemistry prohibits their sole treatment by molecular mechanics (MM) methods. At the same time, a naive separation into low-and high-level regions may be impossible, as important electronic effects may occur in the entire polymer.…”