Bismuth derivatives of 2,3-dicarboxypyrazine and 3,5-dicarboxypyrazole as precursors for bismuth oxide based materials

Abstract

Depending on the experimental conditions, different bismuth derivatives of 2,3-dicarboxypyrazine (2,3-H₂pzdc) were obtained, corresponding to the compositions Bi(2,3-Hpzdc)₃·2H₂O (4) and Bi(2,3-Hpzdc)₂·OH (5). In line with the analytical results and the infrared spectra, high resolution NMR studies (DMSO-) of anhydrous Bi(2,3Hpzdc)₃ (4a) confirmed unequivocally the presence of one free carboxylic acid in the structure. Thermal degradation of 4a in air proceeds in three steps and results in the formation of α-Bi₂O₃ at moderate temperature (451°C). A bismuth derivative of 3,5-dicarboxypyrazole (3,5-H₃Dcp) corresponding to the formula Bi₂(3,5-Dcp)₂·nH₂O (3) was obtained from bismuth nitrate and the dicarboxylic acid in hot water. It decomposes into α-Bi₂O₃ when heated in air at 385°C. The starting compounds and their thermal degradation products were also examined with X-ray photoelectron spectroscopy.