Metal-free photochemical silylations and transfer hydrogenations of benzenoid hydrocarbons and graphene

• The first hydrogenation step of benzene, which is endergonic in the electronic ground state (S 0), becomes exergonic in the first triplet state (T 1). This is in line with Baird's rule, which tells that benzene is antiaromatic and destabilized in its T 1 state and also in its first singlet excited state (S 1), opposite to S 0, 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 T 1-state benzene is excellent at H-atom abstraction, while cyclooctatetraene, aromatic in the T 1 and S 1 states according to Baird's rule, is unreactive. Remarkably, also CVD-graphene on SiO 2 is efficiently transfer-photohydrogenated using formic acid/water mixtures together with white light or solar irradiation under metal-free conditions. © The Author(s) 2016.

Ämnesord

NATURVETENSKAP  -- Kemi -- Organisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Organic Chemistry (hsv//eng)

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering (hsv//eng)

Nyckelord

aromatic compound

benzene

formic acid

graphene

hydrogen

naphthalene

polycyclic aromatic hydrocarbon

carbon

hydrocarbon

irradiation

PAH

photochemistry

solar radiation

Article

geometry

hydrogenation

mathematical analysis

mathematical computing

photoreactivity

quantum chemistry

silylation

white light

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