A fully self-assembled non-symmetric triad for photoinduced charge separation

Abstract

A very efficient and successful metal-mediated strategy towards the formation of an non-symmetric triad is described: appropriate Lewis acid and/or base functions on the molecular components (a naphthalenediimide, an aluminium(III) porphyrin, and a ruthenium(II) porphyrin) lead to the desired product uniquely. The photophysics of the triad was investigated in details using time-resolved spectroscopy in the pico- and nanosecond time domains. The strategy is of great potential interest as, while confining the synthetic effort to the single components, it can give access to a wide range of photoactive systems

Long‐Lived Charge Separation in Novel Axial Donor–Porphyrin–Acceptor Triads Based on Tetrathiafulvalene, Aluminum(III) Porphyrin and Naphthalenediimide

“…Thus, overall the transient absorbance data suggest that in dichloromethane or BN at room temperature the charge‐recombination lifetimes of the states, AlPor .+ ‐NDI .− , TTF .+ ‐AlPor .− , and TTF .+ ‐AlPor‐NDI .− are shorter than a few ns. Such behavior is consistent with that reported recently6d for a similar dyad in which NDI is axially connected to the aluminum porphyrin through a flexible acetate spacer. By using ultrafast spectroscopy, the charge‐separation and charge‐recombination lifetimes of the dyad were found to be 8.1 and 120 ps, respectively, in dichloromethane solution at room temperature.…”

“…There are a number of examples reported in the literature of D–A systems in which the direction of the electron transfer is axial to the porphyrin plane 3c. 6d,f–h, 8 Most of these axial systems show efficient electron transfer between the donor and acceptor components. However, the factors governing electron transfer in these types of complexes have not yet been fully explored.…”

“…Here, we present the preparation and characterization of two AlPor‐based triads in which the nature of the donor, the acceptor, and the bridging groups are varied to study the factors governing the electron transfer in axial triads. As the acceptor, we have chosen naphthalenediimide (NDI) because it is structurally very different from fullerene and has been used in porphyrin‐based D–A complexes before 6d. 8c, 10 Attaching NDI covalently to AlPor gives the new axial dyad aluminum(III) porphyrin–naphthalenediimide (AlPor‐Ph‐NDI; Ph=phenyl) shown in Figure 1.…”

Photocatalytic Hydrogen Evolution with a Self‐Assembling Reductant–Sensitizer–Catalyst System

“…Aluminium(III) pyridylporphyrins are interesting molecular components for the construction of functional supramolecular arrays 19. 20 What makes them particularly attractive is their bifunctional nature, that is, the simultaneous presence of a Lewis acid (the Al center) and a Lewis basic (the meso ‐pyridyl group) function (Figure 1). The Al center can axially bind a variety of ligands, with a particular affinity for oxygen‐based functionalities, whereas the pyridyl function can coordinate to a large variety of transition metals.…”

“…We have recently described the self‐assembly of a triad for photoinduced charge separation based on such a platform 20. In that case, the Lewis acidic and basic functions were used to bind, respectively, an electron acceptor (a carboxyl derivative of naphthalene bisimide) and an electron donor unit (a ruthenium porphyrin).…”