Activating [4 + 4] photoreactivity in the solid-state via complexation: from 9-(methylaminomethyl)anthracene to its silver(i) complexes

The [4 + 4] photoreactivity of the anthracene derivative 9-(methylaminomethyl)anthracene (MAMA) has been investigated in solution, gel medium and in the solid state. While quantitative formation of the cyloaddition photoproduct was achieved upon irradiation at λ = 365 nm of ethanol solutions of MAMA, only partial and slow conversion was detected in gels of low molecular weight gelators, and solid-state reactivity was not observed due to the unfavourable relative orientation of the anthracene moieties in the crystal. In hexafluorophosphate, tetrafluoroborate and nitrate silver(i) complexes, however, 9-(methylaminomethyl)anthracene exhibits a more favourable mutual orientation for the aromatic fragments, and [4 + 4] photoreactivity resulted. All compounds were structurally characterized via single crystal and/or X-ray powder diffraction and by Raman spectroscopy; this last technique proved effective in detection of the photoproduct in all solid state complexes.

Organic aspects. Oxygen-containing functions

In this chapter, most of the reported work deals with the photochemistry of carbonyl compounds; however, the photoreactions of other functions, such as the photo-Claisen rearrangement or the photocleavage of cyclic ethers, are also included. In the present volume, time coverage is 2010–2011, and only original research articles are quoted. In general, reviews or purely theoretical calculations are not systematically included. As usually, the material is organized according to established types of reactions (e.g., Norrish I/II, hydrogen abstraction, Paternò-Büchi, photoelimination, photo-Fries/photo-Claisen, etc.). After presenting the basic photochemical aspects, more specific findings are reported. They include synthetic applications, stereoselectivity, and biological or technological implications. Next, the attention is focused on photochemical reactions in anisotropic media, including (micro)heterogeneous or supramolecular systems, solid matrixes or fully organized crystals. Finally, mechanistic studies based on direct experimental evidence are highlighted, especially when transient absorption spectroscopy or related ultrafast detection are employed.