Tuning Photoinduced Electron Transfer in POM‐Bodipy Hybrids by Controlling the Environment: Experiment and Theory

Abstract

The optical and electrochemical properties of a series of polyoxometalate (POM) oxoclusters decorated with two bodipy (boron‐dipyrromethene) light‐harvesting units were examined. Evaluated here in this polyanionic donor‐acceptor system is the effect of the solvent and associated counterions on the intramolecular photoinduced electron transfer. The results show that both solvents and counterions have a major impact upon the energy of the charge‐transfer state by modifying the solvation shell around the POMs. This modification leads to a significantly shorter charge separation time in the case of smaller counterion and slower charge recombination in a less polar solvent. These results were rationalized in terms of Marcus theory and show that solvent and counterion both affect the driving force for photoinduced electron transfer and the reorganization energy. This was corroborated with theoretical investigations combining DFT and molecular dynamics simulations.

Molecular Nanocomposites with Lanthanide- and Counter-Cation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate

“…Atomistic MD simulations with explicit solvent molecules were performed to determine the behaviour of PcLn-{V12} and (PcLn)2-{V12} (for Ln = Lu) in pure CH2Cl2 using the GROMACS 5.1.2 code 54,55 and a modified AMBER 99 Force Field, 56 which has been successfully employed in previous studies of the dynamic behaviour of POMs in different environments, including aggregation phenomena. [57][58][59] The MD trajectories were calculated imposing 3D periodic boundary conditions. Two different fundamental cubic boxes were used: a (8.5 nm) 3 box containing 8 units (PcLn-{V12} or (PcLn)2-{V12} anions) for the 20 mM (high concentration) solution, and a (11.6 nm) 3 box containing 5 units for the 5 mM (low concentration) solution.…”

Acid-triggering of light-induced charge-separation in hybrid organic/inorganic molecular photoactive dyads for harnessing solar energy

“…33 MeCN. 23 The organotin derivatives display higher negative charge compared to the organosilyl derivatives,…”

“…21,22 Precious metal-free photosensitizers such as zinc porphyrin, perylene, pyrene and boron dipyrromethene (bodipy) have also been applied. 13,14,17,23,24 In these systems, charge-transfer from the sensitizer to the POM occurs either through space or through the bridge, depending on the structure. 25 In bodipy photosensitized POM conjugates, we previously showed that the occurrence and kinetics of photoinduced electron transfer was strongly dependant on the redox properties of both POM and the bodipy sensitizer.…”

“…organosilyl POM derivatives) led to very rapid (50 ps) charge injection upon the excitation of the photosensitizer unit. 14,18,23 This new study focuses on two new Keggin organotin-bodipy (BOD) dyads, K W Sn [BOD] and K Mo Sn [BOD].…”

Substituent Effects in Six(Anilido)‐Five(Thiazole) Membered Ring Boron Difluoride Dyes

“…This is mainly due to the πdelocalization that is symmetrically extended twice or even more, reducing both internal and external reorganization energy. [17][18][19][20][21] Therefore, despite the perhaps intense emission, the small Stokes shift causes significant reabsorption and hence radiative quenching of the emission. In sharp contrast, the asymmetric structure results in uneven π-delocalization, increasing the internal reorganization energy and hence the Stokes shift for reducing the reabsorption.…”