In this work, we present an ew synthetics trategy for fourfold-substituted perylene monoimides via tetrabrominated perylene monoanhydrides. X-ray diffraction analysis unveiled the intramolecular stacking orientation between the substituents and semicircular packing behavior.W eo bserved the remarkable influence of the substituent on the longevity and nature of the excited state upon visible light excitation.I nt he presenceo fp oly(dehydroalanine)-graftpoly(ethylene glycol)g raft copolymers as solubilizing template, the chromophores are capable of sensitizing [Mo 3 S 13 ] 2À clustersi na queous solution for stable visible light driven hydrogen evolution over three days.

The photochemistry of Ru coordination compounds is generally discussed to originate from the lowest lying triplet metal-to-ligand charge-transfer state ( MLCT). However, when heteroleptic complexes are considered, for example, in the design of molecular triads for efficient photoinduced charge separation, a complex structure of MLCT states, which can be populated in a rather narrow spectral window (typically around 450 nm) is to be considered. In this contribution we show that the localization of MLCT excited states on different ligands can affect the following ps to ns decay pathways to an extent that by tuning the excitation wavelength, intermolecular energy transfer from a Ru -terpyridine unit to a fullerene acceptor can be favored over electron transfer within the molecular triad. These results might have important implications for the design of molecular dyads, triads, pentads and so forth with respect to a specifically targeted response of these complexes to photoexcitation.

Covalently linked photosensitizer–polyoxometalate (PS‐POM) dyads are promising molecular systems for light‐induced energy conversion processes, such as “solar” hydrogen generation. To date, very little is known of their fundamental photophysical properties which affect the catalytic reactivity and stability of the systems. PS‐POM dyads often feature short‐lived photoinduced charge‐separated states, and the lifetimes of these states are considered crucial for the function of PS‐POM dyads in molecular photocatalysis. Hence, strategies have been developed to extend the lifetimes of the photoinduced charge‐separated states, either by tuning the PS photophysics or by tuning the POM redox properties. Recently, some of us reported PS‐POM dyads based on cyclometalated Ir III complexes covalently linked to Anderson‐type polyoxometalate. Distinct hydrogen evolution reactivity (HER) of the dyads was observed, which was tuned by varying the central metal ion M of the POM M ( M =Mn 3+ , Co 3+ , Fe 3+ ). In this manuscript, the photoinduced electron‐transfer processes in the three Ir‐POM M dyads are investigated to rationalize the underlying reasons for the differences in HER activity observed. We report that upon excitation of the Ir III complex, ultrafast (sub‐ps) charge separation occurs, leading to different amounts of the charge‐separated states (Ir .+ ‐POM M .− ) generated in the different dyads. However, in all dyads studied, the resulting Ir .+ ‐POM M .− species are short‐lived (sub‐ns) when compared to reference electron acceptors (e.g. porphyrins or fullerenes) reported in the literature. The reductive quenching of Ir .+ ‐POM M .− by a sacrificial donor, triethyl amine (1 m ), to generate the intermediate Ir‐POM M .− is estimated to be very efficient (70–80 %) for all dyads studied. Based on this analyses, we conclude that the yield instead of the lifetime of the Ir .+ ‐POM M .− charge‐separated state determines the catalytic capacity of the dyads investigated. This new feature in the PS‐POM photophysics could lead to new design criteria for the development of novel PS‐POM dyads.

Two novel donor-acceptor molecules, 2,7-diphenylbenzo[1,2-b:4,3-b']difuran-4,5-dicarbonitrile and 2,7-bis(4-methoxyphenyl)benzo[1,2-b:4,3-b']difuran-4,5-dicarbonitrile containing cyano group as the electron acceptor, were synthesized. Their single-crystal structures, molecular packing, and self-assembly behaviors were also investigated. By simple solvent evaporation techniques, these compounds self-assemble into various low-dimensional microstructures that demonstrate distinctive nonlinear optical properties depending on the orientations of their transition dipoles. This study highlights the importance of the transition dipole moment in the construction of low-dimensional molecular materials with highly efficient nonlinear optical properties.

Distance-dependent electron transfer in donor–spacer–acceptor systems is accepted to occur via two distinct mechanisms, that is, by coherent superexchange or incoherent hopping. In general, the rate of electron transfer (k ET) decreases with increasing donor–acceptor distances, irrespective of the actual mechanism being responsible for the process. However, recently Wenger and his group showed that in the frame of the superexchange mechanism electron-transfer rates can pass a maximum when increasing the transfer distance. This manuscript presents an investigation of the forward electron transfer in a series of donor (N-methylphenothiazine)–photocenter (Ru­(II) bis­(terpyridine) complex)–acceptor (N-methylfulleropyrrolidine) triads that reveals the control of the electron-transfer rates by solvent variation to an extent that in acetonitrile an increasing electron-transfer rate is observed with increasing donor–acceptor distance, while in dichloromethane an increase in the separation causes the electron transfer rate to drop. This behavior is qualitatively rationalized based on a recently introduced model. Nonetheless, the quantitative mismatch between the results presented here and the theory indicates that nonexponential distance-dependent couplings will have to be considered in extending the theory.

Understanding the limitations of catalytic processes enables the design of optimized catalysts. Here, femtosecond transient absorption spectroelectrochemistry is used to explore the photophysics of polyoxometalate-based covalent photosensitizer-hydrogen evolution catalyst dyads....

Observation of photoinduced intramolecular charge-separation is difficult for photosensitizer-POM dyads because of rapid backward electron transfer. We report here for the first time on a long-lived charge-separated state (τ = 470 ns) observed in a Ru(ii) bis(terpyridine)-based dyad. Charge-separation occurs despite virtually no driving force and the short intrinsic excited-state lifetime of the photosensitizer.

The covalent attachment of molecular photosensitizers (PS) to polyoxometalates (POMs) opens new pathways to PS‐POM dyads for light‐driven charge‐transfer and charge‐storage. Here, we report a synthetic route for the covalent linkage of BODIPY‐dyes to Anderson‐type polyoxomolybdates by using CLICK chemistry (i. e. copper‐catalyzed azide‐alkyne cycloaddition, CuAAC). Photophysical properties of the dyad were investigated by combined experimental and theoretical methods and highlight the role of both sub‐components for the charge‐separation properties. The study demonstrates how CLICK chemistry can be used for the versatile linkage of organic functional units to molecular metal oxide clusters.