Research Digest 21Initial Studies investigated the coupling of the molecule’s oxidation states with complementary charge transfer (C-T) states through meso-position modifications to produce a molecular switching motif with five discreet interchangeable states, that have different absorption spectra, which can be controlled by photochemical oxidation, chemical oxidation and acidity.1 Subsequent studies have focused on the photophysical properties of the fuchsonarene family of compounds. Upon irradiation with visible light the fuchsonarene compounds enter an excited state, which when exposed to atmospheric molecular oxygen, is capable of generating the reactive oxygen species called singlet oxygen (1O2).2 These species have a vast number of applications including the treatment of various cancers, as chemical synthesis reagents, for land and water remediation and for the destruction of biological entities in the environment (virus, bacteria, etc). We have also recently reported the use of fuchsonarenes as molecular machines.3 2. Research ActivitiesCurrent studies aim to apply these redox active macrocyclic systems to the design of functional materials based on Fig. 1. Structures of resorcinarenes and fuchsonarenes with their cartoon representation. * denotes meso position.Fig. 2. Summary of studies related to chromophore encryption. References 1) Payne et. al., Nat. Commun., 2019, 10, 1007. 2) Payne et. al., Chem. Sci., 2020, 11(10), 2614-2620. 3) Payne et. al., Org. Chem. Front. 2022, 9, 39-50. 4) Bloyet et. al., J. Am. Chem. Soc., 2022, 144, 24, 10830-10843.macrocyclic building blocks to produce novel photosensitizers for photodynamic therapy treatments and to the formation of nanocapsules capable of controllably releasing a guest upon irradiation with visible light. This will be achieved through the modification of the macrocyclic with three varied motifs, such as, water solubilizing groups, targeting motifs and self-assembly motifs to give an effect we call ‘photosensitizer encryption’.4 This research has started to elucidate the structural modifications required to render chromophores capable of self-assembly, whilst maintaining the ability to generate singlet oxygen. This information will be used to ascertain whether these compounds could be applied towards real-world application for molecules capable of generating singlet oxygen. This would include photodynamic therapy applications for the treatment of various diseases, including cancer, and the treatment of contaminated water.These studies represent the first examples of the generation of radical oxygen species for this class of compound and build on the fundamental work previously carried out, which obtained singlet oxygen generation quantum yields competitive with those of porphyrinoids.Applications of Redox Active Macrocycles Capable of Generating Singlet OxygenDaniel T. PAYNE1. Outline of Research Resorcinarenes (Fig. 1) compose a class of phenolic macrocycles that have been intensively investigated from the point-of-view of their host-guest chemistry, in particular involving the formation of oligomacrocyclic capsules. On the other hand, studies of these macrocycles for other applications had been neglected with few studies investigating chemical modifications of the meso-positions (* in fig. 1). Our research to-date has focused on meso-position modifications with phenol groups capable of oxidative processes leading to quinone formation via chemical, electrochemical and photochemical inputs. This allows for changes in the hybridization of the meso-carbon which has led to a number of interesting observations and the introduction of a new class of macrocycles; the fuchsonarenes (Fig. 1).
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