The Twists and Turns of Chiral Chemistry Chirality Is Fundamental to Chemistry, Molecular Biology and Photonics, but Chirality Itself Is Not Often in the Spotlight
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meeting report CHIRAL MATERIALS The twists and turns of chiral chemistry Chirality is fundamental to chemistry, molecular biology and photonics, but chirality itself is not often in the spotlight. Lewis E. MacKenzie and Patrycja Stachelek report on the 2021 Chiral Materials meeting, which explored how chirality manifests in functional materials, and how it can lead to new technological applications. hirality — where an object cannot The first session of the day focused (for example, to optimize conductivity) be superimposed on its mirror on the synthesis and design of chiral and has been experimentally validated4. Cimage — manifests across all molecules. Helicenes — finding use in a Both Lorenzo Di Bari and Francesco Zinna size scales: from fundamental particles variety of applications — were a recurring (University of Pisa) discussed recent work to galactic structures. Perhaps most theme. For example, Matthew Fuchter on the structure and chiroptical properties prominently, chirality underpins chemical (Imperial College London) described recent arising from chiral organic thin films5,6. interactions: twisted molecular structures advances in combining helicenes with The session closed with Lewis MacKenzie will interlock and bind only if their achiral luminescent polymers, to generate (Durham University) describing the chirality allows them. This in turn makes unprecedented strong circularly polarized development a new rapid CPL spectrometer chirality fundamental to the processes of luminescence (CPL) emission via natural for situations where rapid analysis is life. Chirality also drives supramolecular optical activity (rather than structural required, for example, verification of and bulk material properties, with chiral chirality as previously assumed). This CPL-active luminescent security inks7. molecular arrangements altering material approach is particularly promising for the The final session centred on applications, conductivity or the handedness of emitted development of a new-generation organic with a heavy slant towards the nanoscale. circularly polarized photons. Chirality light emitting diodes (OLEDs)1. Michal Ventsislav K. Valev (University of Bath) manipulation therefore gives new ways Juríček (University of Zurich) presented described hyper-Rayleigh scattering to tune and optimize material properties how organic chiral molecules (such as interactions between nanoscale helicoids for organic electronics and 3D display helicenes and helical cethrenes) can be and circularly polarized light8. Malcolm technology applications. Yet, whilst chiral utilized as magnetic switches and chiroptical Kadodwala (University of Glasgow) phenomena are at the heart of a vast array photoswitches with impressive experimental described how spin angular momentum of sciences, most notably chemistry and demonstrations2. Steve Goldup (University from circularly polarized light can be biology, chirality itself is not often the focus of Southampton) described advances in transferred to nanofilms, resulting of attention. processes for the stereoselective synthesis of in remarkable reversible control of ‘Chiral Materials’ is a new and mechanically chiral systems (for example, symmetry in solids9. Bart Kahr (New York independent series of researcher-led mechanically interlocked molecules) that University) described work in unpicking meetings that put chirality centre stage. can be used as enantioselective catalysis3. scale-dependent crystal growth mechanisms, It aspires to link the community of The session closed with Alyssa-Jennifer which — much to the interest of the researchers across the globe who study Avestro (University of York), describing audience — are surprisingly chiral at chirality, albeit with the majority of recent research into the structure and small scales10. speakers hailing from the UK and Europe, properties of helicenes. The meeting was rounded off by A. P. to explore the varied phenomena and The lunch break afforded the opportunity de Silva (Queen’s University Belfast), whose applications that emerge from the topic. to attend the virtual poster session. Many talk focused on the ‘big picture’ stories of his This year’s meeting was the second such of the posters included a short (< 1 minute) career as a scientist. Amongst many topics, event (the first was held in 2019) and was video introduction by the presenter and he touched on the science of photoinduced co-organized by Jessica Wade (Imperial the posters themselves were in PDF electron-transfer sensors and functional College London), Paul McGonigal and format. The video introductions made the image processing with chemicals11. Robert Pal (both Durham University). work very accessible and this innovation Importantly, de Silva emphasized how Due to the COVID-19 crisis, this Chiral would no doubt be welcome at future kindness, mentorship and serendipity are Materials meeting was held via Zoom on 23 conferences, whether virtual or in person. hugely important in scientific research. March 2021 after being delayed from 2020. Poster prizes were awarded by attendee At the end of the day, it felt odd Although many will be disappointed to voting. Carin Lightner (ETH Zurich), to simply switch off from the virtual not have had the opportunity to meet their Leah White (University of Bath), Lizzie meeting with no informal farewells or colleagues in person, the online nature of the Killalea (University of Nottingham) and after-conference dinner. However, the event made it easy for over 370 registered Marco Preuss (Eindhoven University of global accessibility of this free meeting attendees from around the world to attend Technology) all won prizes. was certainly an advantage, and virtual live talks as well as a poster session. Guest The early afternoon session focused on posters with accompanying video speakers discussed their recent research into chiral characterization techniques. Kim introductions can still be found on the 2021 the emergent properties of small molecules, Jelfs (Imperial College London) outlined Chiral Materials website (https://www. thin films, polymers, structural chirality, how computational approaches can be used chiralmaterials.co.uk/). We look forward to chiral matter and light interactions, as to rapidly predict/screen the properties more Chiral Materials meetings in future well as new technological developments in of bulk materials assembled from chiral years, whether they are virtual, in person, spectroscopy and computational screening constituents. This impressive approach or a combination of the best aspects of both techniques (Fig. 1). enables prediction of material properties meeting formats. ❐ NATURE CHEMISTRY | VOL 13 | JUNE 2021 | 521–522 | www.nature.com/naturechemistry 521 meeting report a b c Weakly ordered cylinders Twisted polymer fibril d Ag e 1 2 3 4 F F F F nanohelices 7 7 7 7 SSS- ( ) Δ λλλ Scattered light RRR- ( ) 0 0 0 0 Λ δδδ Circularly polarized at 2 , that is, /2 D D D D ω λ 5 5 5 5 4 3 F incident light at , that is, F 7 ω λ 7 1 1 D D 5 5 Water Fig. 1 | Some of the chiral materials and chiral phenomena presented at Chiral Materials 2021. a, Recent investigations have shown that the large chiroptical effects that manifest in polymer thin films formed from achiral polymers with chiral additives (that is, 1-aza[6]helicene) arise due to magneto-electric coupling (natural optical activity), not structure chirality as previously assumed1. Image provided by Jessica Wade and Matthew Fuchter. b, Varying chiral molecular packing in organic semiconductors alters the charge-carrier mobility properties of the material; computational approaches can be used for mass screening of many configurations to optimize properties such as charge mobility4. Image provided by Kim Jelfs. c, Chiral benzyl nanorods arise through spontaneous nanoscale twisting mechanisms10. Image provided by Bart Kahr. d, A new chiroptical effect: nonlinear optical hyper-Rayleigh scattering at the second harmonic light frequency is dependent on the chirality of Ag nanohelices dispersed in an isotropic liquid8. Image provided by Ventsislav Valev. e, Circular polarized luminescence spectroscopy enables elucidation of excited-state properties of luminescent chiral molecules for applications such as advanced security inks7. Image provided by Robert Pal. Lewis E. MacKenzie ✉ and Patrycja Stachelek References 7. MacKenzie, L., Pålsson, L.-O., Parker, D., Beeby, A. & Pal, R. Department of Chemistry, Durham University, 1. Wade, J. et al. Nat. Commun. 11, 6137 (2020). Nat. Commun. 11, 1676 (2020). 2. Ravat, P., Šolomek, T. & Juríček, M. ChemPhotoChem. 3, 8. Collins, J. T. et al. Phys. Rev. X 9, 011024 (2019). Durham, UK. 180–186 (2019). 9. Kelly, C. et al. Nat. Commun. 11, 5169 (2020). ✉e-mail: [email protected] 3. Maynard, J. R. J. & Goldup, S. M. Chem. 6, 1914–1932 (2020). 10. Li, C. et al. J. Phys. Chem. C 124, 15616–15624 (2020). 4. Schmidt, J. A. et al. Preprint at ChemRxiv https://doi. 11. Ling, J., Naren, G., Kelly, J., Moody, T. S. & de Silva, A. P. org/10.26434/chemrxiv.12451943 (2021). J. Am. Chem. Soc. 137, 3763–3766 (2015). 5. Albano, G., Pescitelli, G. & Di Bari, L. Chem. Rev. 120, Published online: 1 June 2021 10145–10243 (2020). Competing interests https://doi.org/10.1038/s41557-021-00729-8 6. Zinna, F. et al. Adv. Mater. 32, 2002575 (2020). The authors declare no competing interests. 522 NATURE CHEMISTRY | VOL 13 | JUNE 2021 | 521–522 | www.nature.com/naturechemistry.