Polymer thin films that emit and absorb circularly polarised light have been demonstrated with the promise of achieving important technological advances; from efficient, high-performance displays, to 3D imaging and all-organic spintronic devices. However, the origin of the large chiroptical effects in such films has, until now, remained elusive. We investigate the emergence of such phenomena in achiral polymers blended with a chiral small-molecule additive (1-aza[6]helicene) and intrinsically chiral-sidechain polymers using a combination of spectroscopic methods and structural probes. We show that – under conditions relevant for device fabrication – the large chiroptical effects are caused by magneto-electric coupling (natural optical activity), not structural chirality as previously assumed, and may occur because of local order in a cylinder blue phase-type organisation. This disruptive mechanistic insight into chiral polymer thin films will offer new approaches towards chiroptical materials development after almost three decades of research in this area.

We report the self-assembly of a series of highly charged supramolecular complexes in aqueous media composed of cyclobis(4,4'-(1,4-phenylene)bispyridine-p-phenylene)tetrakis(chloride) (ExBox) and three dicationic perylene diimides (PDIs). Efficient energy transfer (ET) is observed between the host and guests. Additionally, we show that our hexacationic complexes are capable of further complexation with neutral cucurbit[7]uril (CB[7]), producing a 3-polypseudorotaxane via the self-assembly of orthogonal recognition moieties. ExBox serves as the central ring, complexing to the PDI core, while two CB[7]s behave as supramolecular stoppers, binding to the two outer quaternary ammonium motifs. The formation of the 3-polypseudorotaxane results in far superior photophysical properties of the central PDI unit relative to the binary complexes at stoichiometric ratios. Lastly, we also demonstrate the ability of our binary complexes to act as a highly selective chemosensing ensemble for the neurotransmitter melatonin.

Abstract:The 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.Light energy transduction is a fundamental phenomenon in the biosphere where living organisms are able to exploit sophisticated noncovalent constructs to transform light into kinetic and potential energy. For instance, visual transduction is initiated by the photoisomerization of retinal in the integral membrane protein Bacteriorhodopsin (BR), and results in the release of a proton to the extracellular environment.1 It is widely accepted that the exquisite control over the light-induced proton transfer is largely imparted by the delicate organization of the protein binding site. At a lower level of complexity, synthetic chemistry has enabled the production of artificial systems that, similarly to BR, can also bind and release protons and substantially larger species through a diversity of light-controlled processes.2 A variety of examples exist, including molecular tweezers, foldamers, cages and macrocycles.3 However, the design and synthesis of light-regulated containers that can operate in an aqueous environment remains a challenge, with only a few examples related to modified cyclodextrins.4 Such materials, provided they show reversible and tight binding to both neutral and charged species, could have significant impact in a variety of areas including photopharmacotherapy, drug delivery and encapsulation technologies.Here we describe a supramolecular container system exhibiting light-controlled encapsulation properties in water. Our multicomponent approach towards photoresponsive binding relies on an optimized design of its individual constituents and comprises the barrel-shaped molecule cucurbit [8] uril (CB[8])5 and a photoresponsive ancillary guest (Chart 1). Recently, we reported the controlled complexation of neutral guests in CB [8] aided by a series of aromatic bis(imidazolium) derivatives.6 Depending on their size, these salts can act as first guests for CB [8] enabling the encapsulation of relatively small second guests includ- †

Pentapeptides containing a Phe residue in the middle of the sequence exhibit ternary complex formation in the presence of cucurbit[8]uril, thus opening new perspectives on supramolecular peptide dimerisation studies.

<div><div><div><p>Polymer thin films that emit and absorb circularly polarised light have been demonstrated with the promise of achieving important technological advances; from efficient, high-performance displays, to 3D imaging and all-organic spintronic devices. However, the origin of the large chiroptical effects in such films has, until now, remained elusive. We investigate the emergence of such phenomena in achiral polymers blended with a chiral small-molecule additive (1-aza[6]helicene) and intrinsically chiral-sidechain polymers using a combination of spectroscopic methods and structural probes. We show that – under conditions relevant for device fabrication – the large chiroptical effects are caused by coupling of electric and magnetic transition dipole moments (natural optical activity), not structural chirality as previously assumed, and may occur because of local order in a cylinder blue phase-type organisation. This disruptive mechanistic insight into chiral polymer thin films will offer new approaches towards chiroptical materials development after almost three decades of research in this area.</p></div></div></div>

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.

The rational design of a flexible molecular box, oAzoBox 4+, 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 oAzoBox 4+ the guest is expelled from the macrocyclic cavity.

The rational design of af lexible molecular box, oAzoBox 4+,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,a llowing for sequestration of small molecule guests in acetonitrile.U pon E!Zp hotoisomerization of oAzoBox 4+ the guest is expelled from the macrocyclic cavity.