title: Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene.
abstract: The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S0), becomes exergonic in the first triplet state (T1). This is in line with Baird's rule, which tells that benzene is antiaromatic and destabilized in its T1state and also in its first singlet excited state (S1), opposite to S0, where it is aromatic and remarkably unreactive. Here we utilized this feature to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) to various extents undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21%). Quantum chemical computations reveal that T1-state benzene is excellent at H-atom abstraction, while cyclooctatetraene, aromatic in the T1and S1states according to Baird's rule, is unreactive. Remarkably, also CVD-graphene on SiO2is efficiently transfer-photohydrogenated using formic acid/water mixtures together with white light or solar irradiation under metal-free conditions.
authors.affiliation: Department of Chemistry-Ångström Laboratory, Box 523, 751 20 Uppsala, Sweden.|Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Raffaello
authors.initials: R
authors.lastname: Papadakis
authors.affiliation: Department of Engineering Sciences, Applied Materials Science, Uppsala University, Box 534, 751 21 Uppsala, Sweden.
authors.forename: Hu
authors.identifier: 0000-0003-1050-8441
authors.initials: H
authors.lastname: Li
authors.affiliation: AstraZeneca R&D Mölndal, Medicinal Chemistry-KH471, 43183 Mölndal, Sweden.
authors.forename: Joakim
authors.initials: J
authors.lastname: Bergman
authors.affiliation: Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Lundstedt
authors.affiliation: Department of Chemistry-Ångström Laboratory, Box 523, 751 20 Uppsala, Sweden.|Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Kjell
authors.identifier: 0000-0002-4191-6790
authors.initials: K
authors.lastname: Jorner
authors.affiliation: Department of Chemistry-Ångström Laboratory, Box 523, 751 20 Uppsala, Sweden.|Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Rabia
authors.initials: R
authors.lastname: Ayub
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
authors.forename: Soumyajyoti
authors.identifier: 0000-0002-3161-4326
authors.initials: S
authors.lastname: Haldar
authors.affiliation: Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Burkhard O
authors.initials: BO
authors.lastname: Jahn
authors.affiliation: Department of Chemistry-Ångström Laboratory, Box 523, 751 20 Uppsala, Sweden.|Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Denisova
authors.affiliation: Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Zietz
authors.affiliation: Department of Chemistry-Ångström Laboratory, Box 523, 751 20 Uppsala, Sweden.|Uppsala Center for Computational Chemistry-UC3, Uppsala University, Box 523, 751 20 Uppsala, Sweden.
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
authors.forename: Biplab
authors.initials: B
authors.lastname: Sanyal
authors.affiliation: Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Helena
authors.initials: H
authors.lastname: Grennberg
authors.affiliation: Department of Engineering Sciences, Applied Materials Science, Uppsala University, Box 534, 751 21 Uppsala, Sweden.
authors.forename: Klaus
authors.initials: K
authors.lastname: Leifer
authors.affiliation: Department of Chemistry-Ångström Laboratory, Box 523, 751 20 Uppsala, Sweden.|Department of Chemistry-BMC, Uppsala University, Box 576, 751 23 Uppsala, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Ottosson