Contributions to the explanation of relaxation processes and photochemical formation of the coloured forms of orthonitrobenzylarenes

Photoreactions of 2-(2′, 4′-dinitrobenzyl)-pyridine ($\text{1}$) and 2, 2′, 4, 4′-tetranitrodiphenylmethane ($\text{2}$) were investigated by means of ps-probe beam spectroscopy. It could be shown, that the electronic ground states of aci-nitro-forms and polymethine forms of flashed compounds were populated after 50 ps (compound $\text{1}$) and 30 ps (compound $\text{2}$) direct from excited states of compounds $\text{1}$ and $\text{2}$. A possible reaction scheme will be given.