Synthesis, Characterization, and Photoinduced Energy and Electron Transfer in a Supramolecular Tetrakis (Ruthenium(II) Phthalocyanine) Perylenediimide Pentad

Abstract

Metal coordination was probed as a versatile approach for designing a novel electron donor/acceptor hybrid [PDIpy(4){Ru(CO)Pc}(4)] (1), in which four pyridines placed at the bay region of a perylenediimides (PDIpy(4)) coordinate with four ruthenium phthalocyanine units [Ru(CO)Pc]. This structural motif was expected to promote strong electronic coupling between the electron donors and the electron acceptor, a hypothesis that was confirmed in a full-fledged physicochemical investigation focusing on the ground and excited state reactivities. As far as the ground state is concerned, absorption and electrochemical assays indeed reveal a notable redistribution of electron density, that is, from the electron-donating [Ru(CO)Pc] to the electron-accepting PDIpy(4). The most important thing to note in this context is that both the [Ru(CO)Pc] oxidation and the PDIpy(4) reduction are rendered more difficult in 1 than in the individual building blocks. Likewise, in the excited state, strong electronic communication is the inception for a rapid charge-transfer process in photoexcited 1. Regardless of exciting [Ru(CO)Pc] or PDIpy(4), spectral characteristics of the [RuPc] radical cation (broad absorptive features from 425 to 600 nm with a maximum at 575 nm, as well as a band centered at 725 nm) and of the PDI radical anion (780 nm maximum) emerge. The correspondingly formed radical ion pair state lasts for up to several hundred picoseconds in toluene, for example. On the other hand, employing more polar solvents, such as dichloromethane, destabilizes the radical ion pair state.

Perylene Bisimide Dye Assemblies as Archetype Functional Supramolecular Materials

“…According to cyclic voltammetry, the energy of the radical ion pair state was estimated to 1.46−1.57 eV depending on the polarity of the solvent. 438 Similarly, the covalently linked porphyrinatozinc-PBI pentad 5-14 ( Figure 58) has been published by Wurthner and coworkers, which could intramolecularly be cyclized by adding ditopic DABCO. Thus, discrete "figure-eight" type macrocycles that further self-assemble on HOPG into highly organized twodimensional arrays were detected by AFM measurements.…”

Ultrafast photodriven intramolecular electron transfer from an iridium-based water-oxidation catalyst to perylene diimide derivatives

“…In a side-to-face ruthenium porphyrin/PDI assembly studied by Iengo, Scandola, Würthner, and coworkers, in which two Ru porphyrins are coordinated to pyridyl groups at the PDI imide positions, charge transfer (τ ¼ 5.6 ps) and recombination (τ ¼ 270 ps) are observed following PDI photoexcitation (16). Related work from the groups of Guldi, Torres, and Wasielewski has demonstrated electron transfer with a ruthenium phthalocyanine/PDI assembly in which the metal complexes are coordinated to the organic dye through pyridyloxy groups at its 1, 6, 7, and 12 positions (9).…”

“…The design of a lightdriven water-splitting system based on molecular catalysts requires a fundamental understanding of the individual electron transfer steps involved in multielectron catalyst activation. To investigate the energetic and kinetic demands of coupling photodriven charge separation and catalysis, many research groups have studied the photophysical properties of covalently linked redox-active organic dyes and transition metal complexes (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). In several cases, electron transfer to or from the metal has been observed and characterized, though energy transfer and intersystem crossing to the chromophore triplet state can be significant competing processes.…”

Exploring the Optimal Synthetic Pathways towards µ‐Carbido Diruthenium(IV) Bisphthalocyaninates

“…RuPcs can be used as triplet injectors [5] and charge collectors [6] in organic photovoltaic devices. [11][12][13] Due to available axial positions and features of Ru coordination chemistry, the RuPcs complexes can be used as catalysts. [7][8][9][10] The ability of RuPcs to form strong coordination bonds with axial N-donor ligands is used to form multicomponent assemblies with well-defined architecture and efficient electronic communication between components.…”