Modular Assembly of Poly(naphthalene diimide) and Ru(II) Dyes for an Efficient Light-Induced Charge Separation in Hierarchically Controlled Polymer Architectures

Abstract

Hierarchically well-defined multielectron acceptor−photosensitizer (A n −P) assemblies were prepared by nitroxide-mediated polymerization of a styrenic naphthalene diimide and subsequent decoration of the chain terminus by a [Ru(dqp) 2 ] 2+ photosensitizer (dqp is 2,6-di(quinolin-8-yl)pyridine). In view of a facile modular design, three synthetic linkage procedures were explored aiming at tailored light-initiated energy and electron transfer processes. The polymers were conveniently purified by column chromatography using aminoor diol-functionalized silica gels and were characterized in detail by NMR, MS, and UV−vis-SEC measurements. The electrochemical and absorption data confirmed the preserved individual redox and optical properties of the building blocks. The detailed steady-state emission measurements revealed an efficient quenching of the photosensitizer exceeding 86−96% with respect to reference complexes and the partial sensitization of/by polymer-based excited states. The results demonstrate the general versatility to construct photoredox-active macromolecules from tailored building blocks.

A Dynamic View of Proton-Coupled Electron Transfer in Photocatalytic Water Splitting

“…The potential problem of charge recombination can be also alleviated by inserting appropriate molecular bridge units with rectifying properties between the dye and the semiconductor 16,59,80,81 or by engineering n/p-supramolecular heterojunctions. [45][46][47][48] We will no further address this point in this work and assume a long-lived oxidized state.…”

“…44 Furthermore, they allow the construction of n/p-supramolecular heterojunctions presenting antiparallel gradients in electron and holes channels to achieve photoinduced long-distance charge separation and reduce charge recombination. [45][46][47][48] Scheme 1. Schematic representation of the proposed photoanode (1) including the acceptorsemiconductor (TiO 2 ), the molecular chromophore NDI 1 , and the Ru-based water oxidation catalyst; (1a) chromophore-semiconductor subsystem employed for the photoinduced electron injection simulation; (1b) chromophore-catalyst subsystem used in the simulation of the first water oxidation catalytic step.…”

Hydrophilic Poly(naphthalene diimide)‐Based Acceptor–Photosensitizer Dyads: Toward Water‐Processible Modular Photoredox‐Active Architectures

“…The monomers 1 and 2 were prepared by a two‐step synthesis from 1,4,5,8‐naphthalenetetracarboxylic dianhydride in analogy to previously described NDIs (Scheme ) . In the first step, the respective monoimide was prepared by reaction with MTEG‐NH 2 or MPEG‐NH 2 550 in DMF under microwave irradiation.…”

“…Hence, the individual parts can be optimized and a high flexibility in the final architecture is achieved. Recently, we demonstrated the suitability of this modular approach by the preparation of a series of acceptor–photosensitizer dyads and, in addition, the desired charge separation was proved by spectroscopic studies …”

“…In this contribution, the synthesis of oligo‐ and poly(ethylene glycol) (PEG) decorated naphthalene diimide (NDI)‐based styrenic polymers is presented in order to increase the hydrophilicity of acceptor–photosensitizer dyads and, thereby, the solubility and processability in polar solvents in comparison with the alkyl‐substituted analogs . The versatility of the general scope is demonstrated by kinetic investigations of the nitroxide‐mediated polymerization (NMP) polymerization and the modular construction of a hydrophilic acceptor–photosensitizer dyad (A−P dyad) using a ruthenium(II) complex.…”