A novel solvatochromic 2-nitroacrylonitrile derived from octamethylferrocenecarbaldehyde

Abstract

Octamethylferrocenecarbaldehyde reacts with excess nitromethane in the presence of potassium tert-butanoxide to give, after silylation and hydrolysis, 2-nitro-3-(octamethylferrocenyl)acrylonitrile in moderate yield. This compound exhibits visible positive solvatochromism. The molar transition energies E_T in 26 different solvents are correlated with the dipolarity-polarizability parameter π* and the hydrogen bond donor acidity α. The results from temperature-dependent Mössbauer spectroscopy suggest that the cyclopentadienyl ring rotation and libration (‘gear wheel’ effect) is inhibited up to a temperature within a few degrees below the melting point, presumably due to the steric requirements of the side chain. The crystal structure has been determined.