On photo-oxidation of single molecules

Fluorescence and fluorescence excitation spectra of terrylene in 9,10-dibromoanthracene matrix were studied at 5 K. Characteristic singlet oxygen phosphorescence, O2(1Δg) → O2(3Σg) with the line maximum at 1272.5 nm, was observed after excitation of terrylene molecules embedded into one of its two sites. It indicates that singlet oxygen, precursor in photo-oxidation of aromatic molecules, can be created only for those oxygen molecules which can form weak van der Waals complex with terrylene. According to quantum-chemical calculations terrylene and oxygen can form complex with the bonding energy 141 cm−1, in which oxygen molecule is located along the long axis of terrylene, ∼0.3 nm apart, with the molecular axis inclined by 110°.

► We studied terrylene in 9,10-dibromoanthracene matrix at 5 K. ► Exciting terrylene we observed singlet oxygen phosphorescence line at 1272.5 nm. ► We concluded that terrylene can form weak van der Waals complex with oxygen molecule. ► According to calculations oxygen is located along the long axis of terrylene.