The oxygen in Earth's atmosphere is there primarily because of water oxidation performed by photosynthetic organisms using solar light and one specialized protein complex, photosystem II (PSII). High-resolution imaging of the PSII 'core' complex shows the ideal co-localization of multi-chromophore light-harvesting antennas with the functional reaction center. Man-made systems are still far from replicating the complexity of PSII as the majority of PSII-mimetics have been limited to photocatalytic dyads based on a 1:1 ratio of a light absorber, generally a Rupolypyridine complex, with a water oxidation catalyst. Here we report the self-assembly of multi-perylene-bisimide chromophores (PBI) shaped to function by interaction with a polyoxometalate water-oxidation catalyst (Ru 4 POM). The resulting [PBI] 5 Ru 4 POM complex shows: a robust amphiphilic structure and dynamic aggregation into large 2D-paracrystalline domains, a red-shifted light-harvesting efficiency > 40%, and favorable exciton accumulation, with a peak quantum efficiency using 'green' photons (λ> 500 nm). The modularity of the building blocks and the simplicity of the non-covalent chemistry offer opportunities for innovation in artificial photosynthesis.
This Minireview sheds light onto the electronic communication between, on one hand, low dimensional nanocarbonssingle and multiwalled 1D carbon nanotubes and 2D grapheneand, on the other hand, a variety of electroactive species en-route to novel electron donor-acceptor conjugates and hybrids in relation to their covalent and non-covalent chemistry, respectively. A common denominator to any of the highlighted conjugates/hybrids is charge transport across different scales, that is, from individual molecular conjugates/hybrids to morphologically controlled devices.
How can catalytic reactions be discovered? Here, a two-dimensional screening strategy for reaction discovery is described. For this purpose, the investigation of single mechanistic steps is merged with combinatorial screening. As a showcase, application to the field of visible light photocatalysis allowed for the discovery of three unexpected cyclization reactions. Extensive mechanistic analysis by advanced spectroscopic and computational tools enabled insights into the underlying molecular processes. In particular, a significantly endergonic sensitization event could be discovered and substantiated by transient absorption spectroscopy.
We describe the formation of charge-transfer complexes that feature electron-donating carbon nanodots (CND) and electron-accepting perylenediimides (PDI). The functionalities of PDIs have been selected to complement those of CNDs in terms of electrostatic and π-stacking interactions based on oppositely charged ionic head groups and extended π-systems, respectively. Importantly, the contributions from electrostatic interactions were confirmed in reference experiments, in which stronger interactions were found for PDIs that feature positively rather than negatively charged head groups. The electronic interactions between the components in the ground and excited state were characterized in complementary absorption and fluorescence titration assays that suggest charge-transfer interactions in both states with binding constants on the order of 8×10(4) M(-1) (25 L g(-1) ). Selective excitation of the two components in ultrafast pump probe experiments gave a 210 ps lived charge-separated state.
We demonstrate the success in self-assembling pyrene-modified Dawson-Wells-type polyoxometalates (POMs) with single walled carbon nanotubes (SWCNTs) by means of p-p interactions. In this context, the immobilization of POMs onto SWCNTs is corroborated by aberration-corrected high-resolution electron microscopy, thermogravimetric analysis, and Raman spectroscopy. From steady-state and time-resolved photophysical techniques we derived evidence for mutual interactions between SWCNTs and POMs in the excited states. The latter are the inception to a charge transfer from the SWCNTs to the POMs. Our results corroborate the suitability of POM-SWCNTs assemblies for photoactive molecular devices.
In this fundamental study, the supramolecular interactions between SWNTs and either symmetrical Zn(II) octa-tert-butylazulenocyanine 1 or a Zn(II) azulenocyanine-phthalocyanine 2 bearing a pyrene unit have been evaluated. The synthetic protocol allowed for the preparation of unsymmetrical azulenocyanine-phthalocyanine molecules, which incorporate reactive hydroxyl functional groups useful for the preparation of more elaborate derivatives, that is, the pyrene containing derivative 2 by an esterification reaction. To shed light onto the mutual interactions between 1 or 2 and SWNT, stable suspensions of SWNT in a mixture of 25% THF and 75% DMF were titrated with variable amounts of 1 or 2. These assays indicate a successful immobilization of azulenocyanine derivatives 1 or 2 onto SWNTs to yield the supramolecular hybrids SWNT/1 and SWNT/2. In this light, the physico-chemical properties of 1 and 2 as well as those of SWNT/1 and SWNT/2 were investigated. From these we conclude strong interactions in the ground state, and a rapid charge separation in the excited state of SWNT/1 or SWNT/2. The accordingly formed radical ion pair states decay with lifetimes of 124 and 137 ps for SWNT/1 and SWNT/2, respectively. Finally, SWNT/1 and SWNT/2 were integrated into photoelectrochemical cells, revealing a response throughout the visible and near-infrared with a moderate IPCE maxima of 2.5%.
A water soluble naphthalenebisimide derivative (NBI) was synthesized and probed to individualize, suspend, and stabilize single wall carbon nanotubes (SWCNT).
Different water-soluble perylenediimides (PDIs) have been used to individualize and stabilize single-walled carbon nanotubes (SWCNTs) in aqueous media. A key feature of the PDIs is that they can be substituted at the bay positions via the addition of two and/or four bromines. This enables control over structural and electronic PDI characteristics, which prompted us to conduct comparative assays with focus on SWCNTs' chirality and charge transfer. Electrochemical, microscopic, and spectroscopic experiments were used to investigate the SWCNT chiral selectivity of PDIs, on the one hand, and charge-transfer reactions between SWCNTs and PDIs, on the other hand.
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