Knoevenagel condensation of ferrocenyl substituted carboxaldehydes with methylene active compounds on inorganic supports and the NLO properties of the resulting push–pull alkenes

We report a new method for the condensation of nonamethylferrocenecarboxaldehyde, 3-ferrocenylacrolein, 5-ferrocenylthiophene-2-carboxaldehyde and 5′-ferrocenyl-2,2′-bithienyl-5-carboxaldehyde inorganic supports, with methylene active compounds on the inorganic supports. In this way, conditions leading to very high yield (>70%) of the product could be achieved. The effect of sonication during the synthesis of nonamethylferrocenecarboxaldehyde is reported and appears to be of great importance. We also report a new method for the synthesis of 3-ferrocenylacrolein. The second-order non-linear optical (NLO) properties of these ferrocenecarboxaldehyde condensation products are measured with the hyper-Rayleigh scattering (HRS) technique. The results of a similar study made for the condensation products of the above-mentioned aldehydes with malononitrile and indan-1,3-indandione are also given.