Complex formation between aliphatic amines and chromogenic calix[4]arene derivatives studied by FT-IR spectroscopy

Complex formation of two calix[4]arene derivatives - containing two ethoxycarbonylmethoxy groups or a bridge including two carboxamide moieties in the coordination sphere - with aliphatic amines (n-octylamine, OA and triethylamine, TEA) were the subject of FT-IR studies. Two nitrophenyl type auxochromic moieties were also present in both of the ligands. Solvent effects were studied in chloroform, diiodomethane and dichloromethane. Presumably, in these reactions, the reactants undergo phenol-amine type interactions and, simultaneously, coordinative interaction takes place between the carbonyl group of the ligand and the protonated form of the aliphatic amine. Complex formation of calixarene 1a with n-octylamine was complete resulting in drastic changes in the FT-IR spectra. Moreover, the possibility of the formation of a new compound by the reaction between the ester type functionalities and octylamine was precluded. The expected ligand was synthesized and its spectra were compared with those of calixarene 1a. In most of the cases of calixarene 1b, the amide moiety of the carboxamide bridge does not participate in the complex formation with the exception of complexes formed in diiodomethane solution and of the 1b-TEA complex observed in dichloromethane.