title: Physicochemical and Electronic Properties of Cationic [6]Helicenes: from Chemical and Electrochemical Stabilities to Far-Red (Polarized) Luminescence.
abstract: The physicochemical properties of cationic dioxa (1), azaoxa (2), and diaza (3) [6]helicenes demonstrate a much higher chemical stability of the diaza adduct 3 (pKR+=20.4, Ered1/2 =-0.72 V) compared to its azaoxa 2 (pKR+=15.2, Ered1/2 =-0.45 V) and dioxa 1 (pKR+=8.8, Ered1/2 =-0.12 V) analogues. The fluorescence of these cationic chromophores is established, and ranges from the orange to the far-red regions. From 1 to 3, a bathochromic shift of the lowest energy transitions (up to 614 nm in acetonitrile) and an enhancement of the fluorescence quantum yields and lifetimes (up to 31 % and 9.8 ns, respectively, at 658 nm) are observed. The triplet quantum yields and circularly polarized luminescence are also reported. Finally, fine tuning of the optical properties of the diaza [6]helicene core is achieved through selective and orthogonal post-functionalization reactions (12 examples, compounds 4-15). The electronic absorption is modulated from the orange to the far-red spectral range (560-731 nm), and fluorescence is observed from 591 to 755 nm with enhanced quantum efficiency up to 70 % (619 nm). The influence of the peripheral auxochrome substituents is rationalized by first-principles calculations.
authors.affiliation: Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet, 30.1211, Geneva 4, Switzerland.
authors.forename: Johann
authors.identifier: http://orcid.org/0000-0002-4117-5638
authors.initials: J
authors.lastname: Bosson
authors.affiliation: Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet, 30.1211, Geneva 4, Switzerland.
authors.forename: Geraldine M
authors.identifier: http://orcid.org/0000-0002-5141-6255
authors.initials: GM
authors.lastname: Labrador
authors.affiliation: Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet, 30.1211, Geneva 4, Switzerland.
authors.forename: Simon
authors.identifier: http://orcid.org/0000-0001-8387-494X
authors.initials: S
authors.lastname: Pascal
authors.affiliation: Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet, 30.1211, Geneva 4, Switzerland.
authors.forename: François-Alexandre
authors.initials: FA
authors.lastname: Miannay
authors.affiliation: Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet, 30.1211, Geneva 4, Switzerland.
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Yushchenko
authors.affiliation: ISM, UMR 5255, University of Bordeaux and CNRS, 33400, Talence, France.
authors.forename: Haidong
authors.initials: H
authors.lastname: Li
authors.affiliation: ISM, UMR 5255, University of Bordeaux and CNRS, 33400, Talence, France.
authors.forename: Laurent
authors.identifier: http://orcid.org/0000-0002-0346-1254
authors.initials: L
authors.lastname: Bouffier
authors.affiliation: ISM, UMR 5255, University of Bordeaux and CNRS, 33400, Talence, France.
authors.forename: Neso
authors.initials: N
authors.lastname: Sojic
authors.affiliation: Department of Chemistry, San José State University, 1 Washington Square, San José, CA, 95192-0101, USA.
authors.forename: Roberto C
authors.initials: RC
authors.lastname: Tovar
authors.affiliation: Department of Chemistry, San José State University, 1 Washington Square, San José, CA, 95192-0101, USA.
authors.forename: Gilles
authors.initials: G
authors.lastname: Muller
authors.affiliation: CEISAM, UMR CNRS 6230, Faculté des Sciences et des Techniques, Université de Nantes, 2, rue de la Houssinière, 44322, Nantes, France), Institut Universitaire de France, 1, rue Descartes, 75005 Paris Cedex 05 (France.
authors.forename: Denis
authors.identifier: http://orcid.org/0000-0002-4217-0708
authors.initials: D
authors.lastname: Jacquemin
authors.affiliation: CEISAM, UMR CNRS 6230, Faculté des Sciences et des Techniques, Université de Nantes, 2, rue de la Houssinière, 44322, Nantes, France), Institut Universitaire de France, 1, rue Descartes, 75005 Paris Cedex 05 (France.
authors.forename: Adèle D
authors.identifier: http://orcid.org/0000-0001-9553-9014
authors.initials: AD
authors.lastname: Laurent
authors.affiliation: Sciences Chimiques de Rennes UMR 6226, CNRS - Université de Rennes 1, Campus de Beaulieu, 35042, Rennes, France.
authors.forename: Boris
authors.identifier: http://orcid.org/0000-0003-3013-0546
authors.initials: B
authors.lastname: Le Guennic
authors.affiliation: Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet, 30.1211, Geneva 4, Switzerland.
authors.forename: Eric
authors.identifier: http://orcid.org/0000-0002-9580-9683
authors.initials: E
authors.lastname: Vauthey
authors.affiliation: Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet, 30.1211, Geneva 4, Switzerland.
authors.forename: Jérôme
authors.identifier: http://orcid.org/0000-0001-6247-8059
authors.initials: J
authors.lastname: Lacour
keywords: circularly polarized luminescence; density functional calculations; electrochemistry; fluorescence; helicenes