Light-Regulated Molecular Trafficking in a Synthetic Water-Soluble Host.

Cucurbit[8]uril (CB[8])-mediated complexation of a dicationic azobenzene in water allows for the light-controlled encapsulation of a variety of second guest compounds, including amino acids, dyes, and fragrance molecules. Such controlled guest sequestration inside the cavity of CB[8] enables the regulation of the thermally induced phase transition of poly(N-isopropylacrylamide)-which is not photosensitive-thus demonstrating the robustness and relevancy of the light-regulated CB[8] complexation.J.D.B. thanks Marie Curie IEF (project no. 273807). S.T.J.R. acknowledges the Cambridge Home and European Scholarship Scheme and the Robert Gardiner memorial scholarship. This work was supported by the EPSRC (reference no. EP/G060649/ 1), an ERC Starting Investigator Grant (project no. 240629), and a Next Generation Fellowship from the Walters-Kundert Foundation. The authors thank HECBioSim (EPSRC grant no. EP/L000253/1) via ARCHER, and the Ada King’s HPC3 service.This is the author accepted manuscript. The final version is available from ACS Publications via http://dx.doi.org/10.1021/jacs.5b1164

A Dynamic and Responsive Host in Action: Light-Controlled Molecular Encapsulation.

The rational design of a flexible molecular box, oAzoBox4+ , incoporating both photochromic and supramolecular recognition motifs is described. We exploit the E↔Z photoisomerization properties of azobenzenes to alter the shape of the cavity of the macrocycle upon absorption of light. Imidazolium motifs are used as hydrogen-bonding donor components, allowing for sequestration of small molecule guests in acetonitrile. Upon E→Z photoisomerization of oAzoBox4+ the guest is expelled from the macrocyclic cavity.S.T.J.R acknowledges the Cambridge Home and European Scholarship Scheme and the Robert Gardiner memorial scholarship. J.D.B. thanks Marie Curie IEF (project number273807). R.S. acknowledges the EC for a Marie Curie fellowship (project number 622711). D.F.R is supported bythe NASA Postdoctoral Program administered by the Uni-versities Space Research Association. This work was supported by the EPSRC (reference number EP/G060649/1), an ERC Starting Investigator Grant (project number 240629),and a Next Generation Fellowship from the Walters-Kundert Foundation. The authors thank HECBioSim (EPSRC grantnumber EP/L000253/1) via ARCHER, and the Ada Kings HPC3 service. Felix Cosmin Mocanu is gratefully acknowledged for assistance in the synthesis of compound 1

Energy and Electron Transfer Dynamics within a Series of Perylene Diimide/Cyclophane Systems.

Artificial photosynthetic systems for solar energy conversion exploit both covalent and supramolecular chemistry to produce favorable arrangements of light-harvesting and redox-active chromophores in space. An understanding of the interplay between key processes for photosynthesis, namely light-harvesting, energy transfer, and photoinduced charge separation and the design of novel, self-assembling components capable of these processes are imperative for the realization of multifunctional integrated systems. We report our investigations on the potential of extended tetracationic cyclophane/perylene diimide systems as components for artificial photosynthetic applications. We show how the selection of appropriate heterocycles, as extending units, allows for tuning of the electron accumulation and photophysical properties of the extended tetracationic cyclophanes. Spectroscopic techniques confirm energy transfer between the extended tetracationic cyclophanes and perylene diimide is ultrafast and quantitative, while the heterocycle specifically influences the energy transfer related parameters and the acceptor excited state.S.T.J.R. thanks the Cambridge Home and European Scholarship Scheme and the Robert Gardiner memorial scholarship. S.T.J.R., A.F. and O.A.S. thank the ERC starting investigator grant ASPiRe (project no. 240629) and the EPSRC (reference no. EP/G060649/1). Femtosecond and nanosecond spectroscopy (R.M.Y.), EPR spectroscopy (M.D.K.) and phosphorescence spectroscopy (Y.W.) were supported as part of the ANSER Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under award no. DE-SC0001059. J.F.S., J.J.H., N.H., N.A.V. and E.D.J. acknowledge the Joint Center of Excellence in Integrated Nano-Systems (JCIN) between KACST and Northwestern University (Project 34-946) for their continued financial support. E.J.D. acknowledges NSF and Ryan fellowships. A.H. and W.M.N. thank the COST Action CM1005 “Supramolecular Chemistry in Water” and the DFG (grant NA-686/5) for financial support.This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/jacs.5b1032

Deoxyribonucleic Acid Encoded and Size-Defined π-Stacking of Perylene Diimides.

Funder: University of CambridgeNatural photosystems use protein scaffolds to control intermolecular interactions that enable exciton flow, charge generation, and long-range charge separation. In contrast, there is limited structural control in current organic electronic devices such as OLEDs and solar cells. We report here the DNA-encoded assembly of π-conjugated perylene diimides (PDIs) with deterministic control over the number of electronically coupled molecules. The PDIs are integrated within DNA chains using phosphoramidite coupling chemistry, allowing selection of the DNA sequence to either side, and specification of intermolecular DNA hybridization. In this way, we have developed a "toolbox" for construction of any stacking sequence of these semiconducting molecules. We have discovered that we need to use a full hierarchy of interactions: DNA guides the semiconductors into specified close proximity, hydrophobic-hydrophilic differentiation drives aggregation of the semiconductor moieties, and local geometry and electrostatic interactions define intermolecular positioning. As a result, the PDIs pack to give substantial intermolecular π wave function overlap, leading to an evolution of singlet excited states from localized excitons in the PDI monomer to excimers with wave functions delocalized over all five PDIs in the pentamer. This is accompanied by a change in the dominant triplet forming mechanism from localized spin-orbit charge transfer mediated intersystem crossing for the monomer toward a delocalized excimer process for the pentamer. Our modular DNA-based assembly reveals real opportunities for the rapid development of bespoke semiconductor architectures with molecule-by-molecule precision.ERC Horizon 2020 (grant agreement No 670405 and No 803326) EPSRC Tier-2 capital grant EP/P020259/1. Winton Advanced Research Programme for the Physics of Sustainability. Simons Foundation (Grant 601946). Swedish research council, Vetenskapsrådet 2018-0023

Photogeneration of Spin Quintet Triplet-Triplet Excitations in DNA-Assembled Pentacene Stacks.

Singlet fission (SF), an exciton-doubling process observed in certain molecular semiconductors where two triplet excitons are generated from one singlet exciton, requires correctly tuned intermolecular coupling to allow separation of the two triplets to different molecular units. We explore this using DNA-encoded assembly of SF-capable pentacenes into discrete π-stacked constructs of defined size and geometry. Precise structural control is achieved via a combination of the DNA duplex formation between complementary single-stranded DNA and the local molecular geometry that directs the SF chromophores into a stable and predictable slip-stacked configuration, as confirmed by molecular dynamics (MD) modeling. Transient electron spin resonance spectroscopy revealed that within these DNA-assembled pentacene stacks, SF evolves via a bound triplet pair quintet state, which subsequently converts into free triplets. SF evolution via a long-lived quintet state sets specific requirements on intermolecular coupling, rendering the quintet spectrum and its zero-field-splitting parameters highly sensitive to intermolecular geometry. We have found that the experimental spectra and zero-field-splitting parameters are consistent with a slight systematic strain relative to the MD-optimized geometry. Thus, the transient electron spin resonance analysis is a powerful tool to test and refine the MD-derived structure models. DNA-encoded assembly of coupled semiconductor molecules allows controlled construction of electronically functional structures, but brings with it significant dynamic and polar disorders. Our findings here of efficient SF through quintet states demonstrate that these conditions still allow efficient and controlled semiconductor operation and point toward future opportunities for constructing functional optoelectronic systems