fotodimerizrile
Fotodimerizrile, or photodimerization, is a chemical reaction in which two molecules combine to form a single dimer upon exposure to light. The process is photochemical, typically initiated by absorption of ultraviolet light, though some substrates can absorb visible light or use photosensitizers to harvest light energy. The reaction can proceed through excited electronic states, with many cases involving a triplet excited state that couples to form a covalent bond, often by a [2+2] cycloaddition between adjacent double bonds to give a cyclobutane-containing dimer. Other pathways involve radical pair formation and subsequent coupling, yielding non-cycloaddition dimers. The exact outcome depends on the substrate, the environment (solution or solid state), and the irradiation wavelength and intensity.
In the solid state, photodimerizrile can exhibit topochemical control, where the relative orientations of the reacting
Common model systems include the photodimerization of anthracene and the [2+2] cycloaddition of simple alkenes; these
Terminology: in Romanian scientific literature the process is commonly referred to as fotodimerizarea; "fotodimerizrile" may appear