Enantiopure distorted ribbon-shaped nanographene combining two-photon absorptionbased upconversion and circularly polarized luminescence
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AuthorCruz, Carlos M.; Márquez, Irene R.; Mariz, Inés F. A.; Blanco Izquierdo, Víctor; Sánchez-Sánchez, Carlos; Sobrado, Jesús M.; Martín-Gago, José A.; Cuerva, Juan M.; Maçôas, Ermelinda; González Campaña, Araceli
Enantiopure distorted ribbon-shaped nanographene combining two-photon absorptionbased upconversion and circularly polarized luminescence. Chem. Sci., 2018, 9, 3917–3924. [DOI: 10.1039/c8sc00427g].
SponsorshipThis project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023). We also thank the Ministerio de Economía y Competitividad (MINECO, Spain) (CTQ2015-70283-P, CTQ2014-53598-R, MAT2014-54231-C4-1P, FIS2016-77578-R) and the “Unidad de Excelencia Química Aplicada a Biomedicina y Medioambiente (UGR)”. A. G. C., C. S. S. and C. M. C. acknowledge funding from MINECO (Spain) for RyC-2013-12943, IJCI-2014-19291 and BES-2016-076371 contracts, respectively. I. R. M. thanks UGR (Spain) for a postdoctoral scholarship. I. M. and E. M. thank the Fundação para a Ciência e a Tecnologia for financial support (IF/00759/2013 and post-doc grant SFRH/BPD/75782/2011). We thank the CSIRC-Alhambra for supercomputing facilities.
Herein we describe a distorted ribbon-shaped nanographene exhibiting unprecedented combination of optical properties in graphene-related materials, namely upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). The compound is a graphene molecule of ca. 2 nm length and 1 nm width with edge defects that promote the distortion of the otherwise planar lattice. The edge defects are an aromatic saddle-shaped ketone unit and a carbohelicene moiety. This system is shown to combine two-photon absorption and circularly polarized luminescence and a remarkably long emission lifetime of 21.5 ns. The helicene is responsible for the chiroptical activity while the push–pull geometry and the extended network of sp2 carbons are factors favoring the nonlinear absorption. Electronic structure theoretical calculations support the interpretation of the results.